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An Overview of the Medusozoa from the Southwestern Atlantic

  • Agustín Schiariti
  • María S. Dutto
  • André Carrara Morandini
  • Renato M. Nagata
  • Daiana Y. Pereyra
  • Francisco A. Puente Tapia
  • Luciana Díaz Briz
  • Gabriel Genzano
Chapter

Abstract

Medusozoans are critical components of coastal and marine ecosystems. They are ubiquitous, living from the surface to the bottom layers of the world’s oceans and tolerating a wide range of environmental conditions. They modulate food webs not only by consuming large quantities of ichthyoplankton and other zooplankton and acting as predators and competitors of varied pelagic organisms including fish but also by being consumed by other predators. Population outbreaks of these gelatinous animals commonly occur over a variety of spatiotemporal scales. These population explosion events have implications for the ecosystem and, usually, for human enterprise. Despite their ecological and socioeconomical importance, there is as yet no attempt to compile existing information on the medusozoan species of the Southwestern Atlantic (SWA). We provide here an overview of the information available regarding several aspects of Medusozoa in the SWA: the characteristics of their life cycles, life histories and “blooms,” and the ecological implications for SWA ecosystems. Guidelines for future research and perspectives on the field are also provided.

Keywords

Jellyfish Gelatinous zooplankton Medusae Ecological roles Societal impacts 

1 Introduction

Medusozoans (i.e., non-anthozoan cnidarians) comprise roughly 3700 species worldwide and are ordinarily divided into four classes: Scyphozoa (true jellyfish), Cubozoa (box jellies), Hydrozoa (hydroids, hydromedusae, siphonophores), and Staurozoa (stalked jellyfish) (Marques and Collins 2004; Daly et al. 2007). The majority of Scyphozoa and Hydrozoa, and all Cubozoa, include pelagic stages (i.e., medusae) in their metagenetic life cycles (Fig. 1). Free-swimming medusae have transparent, soft bodies consisting of ca. 95% of water, conferring a gelatinous consistency typical of all species commonly grouped as “jellyfish.” This common term is also used for other gelatinous zooplankton groups, and it has the advantage of emphasizing the convergent features of transparency, fragility, and planktonic existence that unite these disparate creatures, without the complex taxonomic terminology associated with other terms (Haddock 2004). Species belonging to four different phyla are included under this term. Therefore, “jellyfish” is meant to have no taxonomic implication but rather to evoke these diverse groups of non-crustacean zooplankton that are too fragile to be sampled with conventional net-based systems (Haddock 2004). In the context of this chapter, the word “jellyfish” refers only to the planktonic/pelagic stages of medusozoan species, i.e., scypho-, cubo-, and hydromedusae as well as siphonophores. We deliberately exclude the staurozoans due to a lack of any pelagic/planktonic stages.
Fig. 1

Schematic representation of the medusozoan life cycles. The metagenetic pattern is represented for Hydrozoa (a), Scyphozoa (b), and Cubozoa (c). Holoplanktonic life cycles in Hydrozoa, Trachymedusae (d), Narcomedusae (e), siphonophore colonies (f), and some Scyphozoa (g). Holobenthic life cycles, with fixed abortive medusoid stages in Hydrozoa (h). See details in text (Section 3)

Medusozoans, as do all cnidarians, have highly specialized cells, i.e., the cnidocytes, that contain specialized intracellular structures, the cnidae, unique within the animal kingdom (Morandini et al. 2016a). Nematocysts, a type of cnidae that are probably the most complex secretion products of single animal cells, have enabled the group to achieve enormous success as predators with little investment in the elaboration of sensory and morphological specializations that characterize most predators. In a sense, they have been considered as “little more than a gut with tentacles” (Kass-Simon and Scappaticci 2002). With very few exceptions, cnidarian jellyfish are carnivores that use their cnidae to kill their prey, which include, depending on the species, other jellyfish, crustaceans, veliger larvae, fish eggs, and larvae (Genzano et al. 2014). Some jellyfish, however, are microphagous or even contain symbiotic zooxanthellae. Jellyfish are ubiquitous, inhabiting all marine ecosystems of the world over more than 500 million years. They can range in size from a few mm to more than 1 m in bell diameter, thus being parts of the meso-, macro-, and megazooplankton. They are ecologically and evolutionarily important and relevant to human affairs. They present interesting conceptual problems, not only because of the key position they occupy in the evolutionary tree but also due to distinctive aspects of their biology and development (Mackie 2002; Morandini et al. 2014; Technau et al. 2015).

Research on zooplankton has been historically oriented toward the non-gelatinous species (mostly copepods) that provide the bulk of the food for commercially important fish stocks (Haddock 2004). These organisms present size, body structures, and spatial and temporal distributions that can be reliably represented with conventional plankton net samples. However, different devices are needed to establish patterns of abundance, distribution, behavior, and trophic ecology of soft-bodied gelatinous zooplankters, particularly when they occur in mass aggregations. The watery bodies of medusozoans are badly damaged by traditional plankton tows, often posing unanswerable questions regarding taxonomy and phylogeny and preventing accurate abundance and biomass estimates. Therefore, pelagic cnidarians usually have been omitted from routine oceanographic sampling. Since the mid-twentieth century, the development and improvement of collection and observation techniques (e.g., submersibles, remotely operated vehicles, SCUBA, acoustics, video and optical devices) have painted a dramatically different picture of medusozoan diversity from that provided by typical net tows. These sampling techniques provide access to specimens which can be used in natural experiments and not just poorly enumerated. This is essential to study their natural history, physiology, and ecology and is perhaps the most significant impact of modern collection techniques (Haddock 2004).

Research takes place within the larger context of human society, and as with any investigation, one must consider potential benefits that justify support using public funds.

Within this framework, interest in medusozoans has expanded in response to the problems generated for human enterprises by their population outbreaks (e.g., Purcell et al. 2007). Meanwhile, the economic exploitation of different scypho- and hydromedusae species has increased, which is the other side of the same coin (e.g., Purcell et al. 2013; Lange et al. 2016; Brotz et al. 2017). Because of these negative and positive interactions between “blooming species and business,” the factors regulating jellyfish abundance have emerged as one of the big questions in jellyfish research. Today jellyfish are widely acknowledged as keystone species shaping pelagic communities in marine ecosystems (Pauly et al. 2009; Boero 2013). The worldwide knowledge about jellyfishes is patchy, as it is the distribution of the animals; this means that some geographic areas are better known than others. In the Southwestern Atlantic (SWA), jellyfish research is still in its infancy. Our main goal here is to review the state of the art in jellyfish research and additionally drawing attention to the need for directed research programs and international cooperation. Thus, our contribution is organized in the following topics: species composition, biological patterns of life cycles and blooms, ecological roles of jellyfishes, interaction with man, and future perspectives.

2 Jellyfish Species Composition in the SWA

In the SWA region, 689 medusozoan species or morphotypes have been recognized so far (see Oliveira et al. 2016). Of these, 335 (49%) have a pelagic medusa-like stage (Table 1), although a few species have “unusual” habits and can live on the bottom or on other substrates like algae (e.g., Cassiopea, Cladonema, Staurocladia). In addition, the pelagic phase can be comprised of polypoid forms that can live in the planktonic or neustonic environment (e.g., Porpita, Velella). The 335 species/morphotypes with a pelagic medusa stage can be classified into the following classes:
  • Cubozoa: 5 species are reported for the SWA , from a total of ~50 species known worldwide (Kingsford and Mooney 2014): Alatina alata, Chiropsalmus quadrumanus, Chiropsalmus zygonema, Tamoya haplonema, and Tripedalia cystophora.

  • Scyphozoa: there are 21 species (20 confirmed species + Aurelia s.l.) registered for the SWA, out of ~200 known worldwide (Daly et al. 2007): Atolla chuni, Atolla wyvillei, Nausithoe atlantica, Nausithoe aurea, Nausithoe punctata, Linuche unguiculata, Periphylla periphylla, Cassiopea andromeda, Lychnorhiza lucerna, Phyllorhiza punctata, Stomolophus meleagris, Desmonema comatum, Desmonema gaudichaudi, Chrysaora lactea, Chrysaora plocamia, Pelagia noctiluca, Drymonema gorgo, Phacellophora camtschatica, Poralia rufescensAurelia sp., and Stygiomedusa gigantea.

  • Hydrozoa: there are 278 species ( 222 confirmed species + 56 identified only to genus) recorded for the SWA area, from ~3500 species known worldwide (Daly et al. 2007): 53 Trachylinae (21 Trachymedusae, 23 Narcomedusae, 9 Limnomedusae), 92 Siphonophorae (2 Cystonectae, 22 Physonectae , 68 Calycophorae), 71 Anthoathecata (13 Aplanulata, 16 Capitata, 42 Filifera), and 62 Leptothecata (3 Incertae sedis, 7 Laodiceida, 52 Statocysta).

Table 1

Medusozoan species composition reported from the Southwestern Atlantic waters. Only taxa determined to species level having planktonic/pelagic stages were considered, comprising 268 hydrozoan, 20 scyphozoan, and 5 cubozoan species or morphotypes (according to Oliveira et al. 2016). (*) species with described life cycles. For Hydrozoa species, see Section 3.3

Podocoryna loyola (Haddad et al., 2014) (*)

Dimophyes arctica (Chun, 1897) (*)

Podocoryna tenuis (Browne, 1902) (*)

Diphyes bojani (Eschscholtz, 1829) (*)

Podocoryna uniformis (Stampar et al., 2006) (*)

Diphyes chamissonis (Huxley, 1959) (*)

Stylactaria hooperii (Sigerfoos, 1899) (*)

Diphyes dispar (Chamisso & Eysenhardt, 1821) (*)

Niobia dendrotentaculata (Mayer, 1900)

Eudoxoides mitra (Huxley, 1859) (*)

Oceania armata (Kölliker, 1853)

Eudoxoides spiralis (Bigelow, 1911) (*)

Turritopsis nutricula (McCrady, 1857b) (*)

Gilia reticulata (Totton, 1954) (*)

Amphinema australis (Mayer, 1900) (*)

Lensia achilles (Totton, 1941) (*)

Amphinema dinema (Perón & Lesueur, 1809) (*)

Lensia ajax (Totton, 1941) (*)

Annatiara affinis (Hartlaub, 1914)

Lensia campanella (Moser, 1917) (*)

Cirrhitiara superba (Mayer, 1900)

Lensia challengeri (Totton, 1954) (*)

Halitholus intermedius (Browne, 1902) (*)

Lensia conoidea (Keferstein & Ehlers, 1860) (*)

Leuckartiara octona (Fleming, 1823) (*)

Lensia cossack (Totton, 1941) (*)

Leuckartiara zacae (Bigelow, 1940) (*)

Lensia fowleri (Bigelow, 1911) (*)

Merga tergestina (Neppi & Stiasny, 1912) (*)

Lensia grimaldii (Leloup, 1933) (*)

Neoturris pileata (Forskal, 1775) (*)

Lensia hardy (Totton, 1941) (*)

Pandea conica (Quoy & Gaimard, 1827) (*)

Lensia havock (Totton, 1941) (*)

Stomotoca atra (L. Agassiz, 1862) (*)

Lensia hostile (Totton, 1941) (*)

Proboscidactyla mutabilis (Browne, 1902) (*)

Lensia hotspur (Totton, 1941) (*)

Proboscidactyla ornata (McCrady, 1859) (*)

Lensia hunter (Totton, 1941) (*)

Halitiara Formosa (Fewkes, 1882) (*)

Lensia leloupi (Totton, 1954) (*)

Lizzia blondina (Forbes, 1848)

Lensia lelouveteau (Totton, 1941) (*)

Podocorynoides minima (Trinci, 1903)

Lensia meteori (Leloup, 1934) (*)

Rathkea formosissima (Browne, 1902)

Lensia multicristata (Moser, 1925) (*)

Rathkea octopunctata (M. Sars, 1835)

Lensia subtilis (Chun, 1886) (*)

Order Incertae sedis

Lensia subtiloides (Lens & van Riemsdijk, 1908) (*)

Dipleurosoma collapsum (Mayer, 1900)

Lensia cf. tottoni (Daniel & Daniel, 1963) (*)

Hebella furax (Millard, 1957) (*)

Muggiaea atlantica (Cunningham, 1892) (*)

Hebella scandens (Bale, 1888) (*)

Muggia eakochii (Will, 1844) (*)

Order Laodicea

Sulculeolaria biloba (Sara, 1846) (*)

Laodicea indica (Browne, 1905)

Sulculeolaria chuni (Lens & van Riemsdijk, 1908) (*)

Laodicea minuscula (Vannucci, 1957)

Sulculeolaria monoica (Chun, 1888) (*)

Laodicea ocellata (Babnik, 1948)

Sulculeolaria quadrivalvis (Blainville, 1834) (*)

Laodicea pulchra (Browne, 1902)

Sulculeolaria turgida (Gegenbaur, 1853) (*)

Laodicea undulata (Forbes & Goodsir, 1851)

Hippopodius hippopus (Forskål, 1776)

Staurophora mertensii (Brandt, 1835)

Vogtia glabra (Bigelow, 1918)

Modeeria rotunda (Quoy & Gaimard, 1827) (*)

Vogtia pentacantha (Kölliker, 1853)

Order Statocysta

Vogtia serrata (Moser, 1925)

Tetracanna octonema (Goy, 1979)

Vogtia spinosa (Keferstein & Ehlers, 1861)

Cirrholovenia tetranema (Kramp, 1959) (*)

Amphicaryon acaule (Chun, 1888) (*)

Cosmetirella davisi (Browne, 1902)

Amphicaryon ernesti (Totton, 1954) (*)

Cosmetira pilosella (Forbes, 1848)

Amphicaryon peltifera (Haeckel, 1888) (*)

Halopsis ocellata (A. Agassiz, 1865)

Phylum Cnidaria

Mitrocomella brownei (Kramp, 1930)

Subphylum Medusozoa

Mitrocomella frigida (Browne, 1910)

Class Hydrozoa (cont.)

Mitrocomella polydiademata (Romanes, 1876)

Order Calycophorae(cont.)

Phialella falklandica (Browne, 1902) (*)

Lilyopsis rosea (Chun, 1885)

Aequorea coerulescens (Brandt, 1838) (*)

Maresearsia praeclara (Totton, 1954) (*)

Aequorea forskalea (Péron & Lesueur, 1809) (*)

Nectadamas diomedeae (Bigelow, 1911)

Aequorea globosa (Eschscholtz, 1829) (*)

Nectopyramis natans (Bigelow, 1911) (*)

Aequorea macrodactyla (Brandt, 1835) (*)

Nectopyramis thetis (Bigelow, 1911) (*)

Rhacostoma atlanticum (L. Agassiz, 1851)

Praya dubia (Quoy & Gaimard, 1833) (*)

Zygocanna vagans (Bigelow, 1912)

Rosacea cymbiformis (Delle Chiaje, 1822)

Blackfordia virginica (Mayer, 1910) (*)

Rosacea plicatasensu (Bigelow, 1911)

Eirene lactea (Mayer, 1900) (*)

Sphaeronectes fragilis (Carré, 1967) (*)

Eirene viridula (Péron & Lesueur, 1809)

Sphaeronectes koellikeri (Huxley 1859) (*)

Eutima coerulea (L. Agassiz, 1862) (*)

Order Limnomedusae

Eutima cf. gegenbauri (Haeckel, 1874) (*)

Aglauropsis agassizii (F. Müller, 1865) nomen dubium

Eutima gentiana (Haeckel, 1879)

Aglauropsis conantii (Browne, 1902)

?Eutima gracilis (Forbes & Goodsir, 1851)

Aglauropsis kawari (Moreira & Yamashita, 1972)

Eutima mira (McCrady, 1859) (*)

Cubaia aphrodite (Mayer, 1894)

Phylum Cnidaria

Gonionemus vertens (A. Agassiz, 1862) (*)

Subphylum Medusozoa

Gossea brachymera (Bigelow, 1909)

Class Hydrozoa (cont.)

Olindias sambaquiensis (F. Müller, 1861)

Order Statocysta (cont.)

Vallentinia falklandica (Browne, 1902)

Eutima sapinhoa (Narchi & Hebling, 1975) (*)

Vallentinia gabriellae (Vannucci Mendes, 1948)

Eutonina scintillans (Bigelow, 1909) (*)

Order Narcomedusae

Irenium teuscheri (Haeckel, 1879)

Aegina citrea (Eschscholtz, 1829) (*)

Phialopsis diegensis (Torrey, 1909)

Aeginura grimaldii (Maas, 1904) (*)

Mitrocomium cirratum (Haeckel, 1879) (*)

Solmundella bitentaculata (Quoy & Gaimard, 1833) (*)

Malagazzia carolinae (Mayer, 1900)

Cunina duplicata (Maas, 1893) (*)

Octophialucium haeckeli (Vannucci & Moreira, 1966) (*)

Cunina frugifera (Kramp, 1948) (*)

Octophialucium bigelowi (Kramp, 1955) (*)

Cunina globosa (Eschscholtz, 1829) (*)

Eucheilota diademata (Kramp, 1959b) (*)

Cunina octonaria (McCrady, 1859) (*)

Eucheilota duodecimalis (A. Agassiz, 1862) (*)

Cunina peregrina (Bigelow, 1909) (*)

Eucheilota foresti (Goy, 1979) (*)

Solmissus atlantica (Zamponi, 1983) nomen dubium (*)

Eucheilota maculata (Hartlaub, 1894) (*)

Solmissus faberi (Haeckel, 1879) (*)

Eucheilota menoni (A. Agassiz, 1862) (*)

Solmissus marshalli (Agassiz & Mayer, 1902) (*)

Eucheilota paradoxica (Mayer, 1900) (*)

Pegantha clara (Bigelow, 1909) (*)

Eucheilota ventricularis (McCrady, 1859) (*)

Pegantha laevis (Bigelow, 1909) (*)

Clytia brunescens (Bigelow, 1904) (*)

Pegantha martagon (Haeckel, 1879) (*)

Clytia discoida (Mayer, 1900) (*)

Pegantha rubiginosa (Kölliker, 1853) (*)

Clytia elsaeoswaldae (Stechow, 1914) (*)

Pegantha triloba (Haeckel, 1879) (*)

Clytia gracilis (M. Sars, 1850) (*)

Solmaris corona (Keferstein & Ehlers, 1861) (*)

Clytia hemisphaerica (Linnaeus, 1767) (*)

Solmaris flavescens (Kölliker, 1853) (*)

Clytia linearis (Thornely, 1900) (*)

Tetraplatia volitans (Busch, 1851) (*)

Clytia lomae (Torrey, 1909) (*)

Order Trachymedusae

Clytia noliformis (McCrady, 1859) (*)

Geryonia proboscidalis (Forskål, 1775) (*)

Clytia simplex (Browne, 1902) (*)

Liriope tetraphylla (Chamisso & Eysenhardt, 1821) (*)

Gastroblasta ovale (Mayer, 1900) (*)

Botrynema brucei (Browne, 1908) (*)

Obelia bidentata (Clark, 1875) (*)

Halicreas minimum (Fewkes, 1882) (*)

Obelia dichotoma (Linnaeus, 1758) (*)

Halitrephes maasi (Bigelow, 1909a) (*)

Obelia geniculata (Linnaeus, 1758) (*)

Aglantha digitale (F. Müller, 1776) (*)

Obelia longissima (Pallas, 1766) (*)

Aglantha elata (Haeckel, 1879) (*)

Order Cystonectae

Aglaura hemistoma Péron & Lesueur, 1809 (*)

Physalia physalis (Linnaeus, 1758) (*)

Amphogona apicata (Kramp, 1957) (*)

Rhizophysa filiformis (Forskål, 1775) (*)

Amphogona apsteini (Vanhöffen, 1903) (*)

Order Physonectae

Colobonema sericeum (Vanhöffen, 1903) (*)

Agalma elegans (Sars, 1846)

Crossota brunnea (Vanhöffen, 1903) (*)

Agalma okeni (Eschscholtz, 1825) (*)

Homoeonema platygonon (Browne, 1903) (*)

Athorybia rosacea (Forskål, 1775)

Pantachogon haeckeli (Maas, 1893) (*)

Halistemma rubrum (Vogt, 1852)

Persa incolorata (McCrady, 1859) (*)

Melophysa melo (Quoy & Gaimard, 1827)

Rhopalonema velatum (Gegenbaur, 1856) (*)

Erenna richardi (Bédot, 1904)

Sminthea eurygaster (Gegenbaur, 1856) (*)

Forskalia contorta (Milne Edwards, 1841)

Class Scyphozoa

Forskalia edwardsi (Kölliker, 1853)

Order Coronatae

Physophora hydrostatica (Forskål, 1775) (*)

Atolla chuni (Vanhöffen, 1902)

Bargmannia elongata (Totton, 1954) (*)

Atolla wyvillei (Haeckel, 1880)

Pyrostephos vanhoeffeni (Moser, 1925) (*)

Linuche unguiculata (Swartz, 1788) (*)

Rhodalia rotunda (Haeckel, 1888) (*)

Nausithoe atlantica (Broch, 1914)

Cordagalma ordinatum (Haeckel, 1888) (*)

Nausithoe aurea (Silveira & Morandini, 1997) (*)

Lychnagalma utricularia (Claus, 1879) (*)

Nausithoe punctata (Kölliker, 1853) (*)

Marrus antarcticus (Totton, 1954)

Periphylla periphylla (Péron & Lesueur, 1810) (*)

Marrus cf. orthocanna (Kramp, 1942)

Order Rhizostomeae

Halistemma striata (Totton, 1965)

Cassiopea andromeda (Forskål, 1775) (*)

Melophysa melo (Quoy & Gaimard, 1827)

Lychnorhiza lucerna (Haeckel, 1880) (*)

Nanomia bijuga (Delle Chiaje, 1841) (*)

Phyllorhiza punctata (von Lendenfeld, 1884) (*)

Apolemia uvaria (Lesueur, 1811)

Stomolophus meleagris (L. Agassiz, 1860) (*)

Order Calycophorae

Order Semaeostomeae

Abyla bicarinata (Moser, 1925)

Desmonema comatum (Larson, 1986)

Abyla haeckeli (Lens & van Riemsdijk, 1908)

Desmonema gaudichaudi (Lesson, 1832)

Abyla trigona (Quoy & Gaimard, 1827)

Drymonema gorgo (Müller, 1883)

Abylopsis eschscholtzii (Huxley, 1859)

Chrysaora lactea (Eschscholtz, 1829) (*)

Abylopsis tetragona (Otto, 1823)

Chrysaora plocamia (Lesson, 1830) (*)

Bassia bassensis (Quoy & Gaimard, 1833) (*)

Pelagia noctiluca (Forskål, 1775) (*)

Ceratocymba dentata (Bigelow, 1918)

Phacellophora camtschatica (Haeckel, 1880) (*)

Ceratocymba leuckarti (Huxley, 1859)

Aurelia sp. (*)

Ceratocymba sagittata (Quoy & Gaimard, 1827)

Stygiomedusa gigantea (Browne, 1910)

Poralia rufescens (Vanhöffen, 1902)

Enneagonum hyalinum (Quoy & Gaimard, 1827)

Class Cubozoa

Chuniphyes moserae (Totton, 1954)

Order Carybdeidae

Chuniphyes multidentata (Lens & van Riemsdijk, 1908)

Alatina alata (Reynaud, 1830) (*)

Crystallophyes amygdalina (Moser, 1925)

Tamoya haplonema (F. Müller, 1859)

Heteropyramis crystallina (Moser, 1925)

Tripedalia cystophora (Conant, 1897) (*)

Heteropyramis maculata (Moser, 1925)

Order Chirodropida

Chelophyes appendiculata (Eschscholtz, 1829) (*)

Chiropsalmus quadrumanus (F. Müller, 1859)

 

Chiropsalmus zygonema (Haeckel, 18 = 80)

3 Life Cycles, Life Histories, and Jellyfish Blooms

3.1 Medusozoan Life Cycles: General Patterns

Life cycle can be defined as the continuous sequence of changes undergone by an organism from one primary form, as a gamete, to the development of the same form again (Stearns 1992). In the general medusozoan life cycle, fertilization of gametes results in a planula larva that settles onto the substrate and metamorphoses into a sessile polyp. The polyps reproduce only asexually by producing more polyps. When certain environmental conditions are met, polyps begin producing ephyrae (i.e., young medusae), which are released into the water column and become adult medusae (Fig. 1). This basic scheme has been described as a metagenetic life cycle, alternation (or succession) of generations (or stages) (see Morandini et al. 2016b).

From this general life cycle , an unparalleled diversity and plasticity have been reported, perhaps because the anatomical and physiological simplicity of cnidarians makes them evolutionarily plastic (Boero et al. 1997; Fautin 2002; Jarms 2010). Yet, an acceptable approach can be derived from the general pattern described above: the life cycle of the typical medusozoan comprises a polyp stage, which reproduces asexually in the benthos, and a medusoid stage, which reproduces sexually in the plankton, with the gametes and the planula larvae as links in between them (Fig. 1).

This general pattern is present in the majority of scyphozoans, most hydrozoans and all cubozoans, but differs from staurozoan life cycles in which the pelagic stage has been reduced to a creeping benthic planula (Miranda et al. 2010). While there is great variation in medusozoan life cycles, there is congruence between the variations and the origins of major medusozoan taxa (Collins 2002). The way in which the medusa stage is produced is a good example: the Hydrozoa produce medusae by budding, the Scyphozoa by strobilation , and the Cubozoa by complete metamorphosis of a polyp into a medusa (Fig. 1).

Scyphozoa is the taxon with the highest proportion of species among medusozoans with the typical metagenetic life cycle. Most scyphomedusae are produced asexually by individual polyps (i.e., scyphistomae) through the process of strobilation (i.e., transverse fission followed by metamorphosis) (Fig. 1) (Jarms 2010). During strobilation, polyps lose their tentacles and mouth and reduce their size. After ephyrae are released into the water column, polyps can reattain their normal size, shape, and function within a few days. Polyps can be then capable of producing new polyps and ephyrae again, if suitable environmental conditions are met. Within the general metagenetic life cycle, hydrozoans exhibit the greatest number of variations. In the typical case, planula larvae metamorphose into primary polyps that reproduce asexually in the benthos. However, the polyps of the majority of species bud off additional polyps that remain connected, producing a branching colony . The colony, in turn, can produce new buds that either enlarge the mother colony or detach and form another colony. Hydromedusae are produced by budding instead of by strobilation (Boero et al. 1997) (Fig. 1).

The life cycle of cubozoans differs from that of scyphozoans and hydrozoans in the way medusae are produced. Cubomedusae also develop asexually from benthic polyps; however, the whole polyp (in most species) transforms into a medusa by metamorphosis, leaving no polyp remnant behind (Fig. 1). In Cubozoa, each fertilized ovum becomes a planula larva, which in turn forms a single polyp that becomes a single medusa. In contrast, the Scyphozoa and Hydrozoa life cycles involve what has been referred to as “larval” amplification (Boero 2013), when a single polyp (or a colony) can produce asexually thousands of polyps and medusae by repeating the processes strobilation and budding several times within a single annual cycle (Bouillon et al. 2006; Morandini et al. 2016a).

Although with some variations, the majority of Scyphozoa and Hydrozoa, and all Cubozoa, present the described general life cycle characterized by these alternations of body forms (polypoid/medusoid), types of reproduction (asexual/sexual), and environments (benthos/plankton). Hereafter, deviations from this pattern that we comment upon are based on examples among the species present in the SWA . More detailed revisions of medusozoan life cycles can be consulted in Collins (2002), Jarms (2010), and Toshino et al. (2015).

3.2 Medusozoan Life Cycles: Deviations from the Pattern

Several different variations of the general metagenetic life cycle can be found among medusozoans groups, consisting of reduction of the polypoid stage or the medusa stage and concomitant simplifications (or increased complexity) within each form (Fig. 1). The simplest examples can be found at both the extremes of the pattern; there are species that lack “one half” of the general scheme. Several species exhibit holopelagic (=holoplanktonic) life cycles, with medusae reproducing sexually in the plankton with no benthic, polypoid, or asexually reproducing stages. The examples from the SWA are the scyphozoans Pelagia noctiluca and Periphylla periphylla. Also, species of Trachymedusae (Hydrozoa) are holoplanktonic , with a medusa stage that reproduces sexually in the plankton and a completely absent benthic polypoid stage (Table 1). But even within holopelagic life cycles, several variations can be found with representatives in the SWA. For example, Narcomedusae species have holoplanktonic life cycles that include a polypoid stage parasitic on other medusae. Despite having an asexually reproducing polypoid stage, these species occur only in the pelagic realm. Holoplanktonic life cycles are also present in siphonophores that have a polymorphic organization with polypoid and medusoid forms included in the same colony (Fig. 1) (Carré 1969; Kirkpatrick and Pugh 1984; Carré and Carré 1991).

A special case that perhaps constitutes the best example of the extraordinary diversity of medusozoan life cycles is the so-called immortal jellyfish Turritopsis nutricula (Hydrozoa) (see Piraino et al. 1996) that is also present in the SWA. Life cycles generally include a progression of developmental stages leading to sexually mature adults (e.g., the medusa stage). Although in a few hydrozoans ontogeny reversal is possible (i.e., a change the sequence of stages), this never occurs after the onset of sexual reproduction. Normally, medusae have a limited life span, with a growth phase leading to sexual maturity and spawning , followed by cell disintegration and death. The onset of sexual reproduction has been hypothesized to be a point of no return in the ontogenetic sequence of any living organism (Stearns 1992). However, Piraino et al. (1996) have found in T. nutricula one of the most surprising cases in the entire animal kingdom: all its stages of development – from newly liberated to fully mature individuals – can transform back into colonial hydroids. Because of this extraordinary ability, this species has been considered as “immortal.” This case does not deviate from the described general pattern , just adds the most astonishing variation.

Briefly, whereas the basic scheme of medusozoan life cycles can be thought of as alternation between a pelagic, sexually reproducing medusa stage and a benthic, asexually reproducing polyp (or colony) stage, it is possible to find many of the imaginable deviations from this general pattern. Thus, some species are pelagic as polypoid forms, and in some others the benthic stage is a medusa (or some medusoid form), and both types of reproduction (sexual and asexual) can be conducted in different species by medusae or by polyps, and either can be found in both the planktonic and benthic environments. As stated by Fautin (2002), cnidarian reproduction is more variable than previously thought, and examples of this unparalleled diversity of life cycles and reproductive strategies are found within the region considered in this study, including one species that “seems to cheat death.”

3.3 Jellyfish Blooms

Medusozoans regularly show natural events of massive proliferation that are triggered by the cyclical occurrence of favorable environmental conditions. As an intrinsic feature of cnidarians, pelagic stages can be extremely abundant during certain periods; even if rarely found for years, they may massively (and oddly) reappear (Boero 2013). It is likely that at least three conditions must be favorable simultaneously to allow jellyfish population explosions (see Box 1): (1) optimum values of physical factors, such as temperature, (2) suitable food in terms of both quality and quantity for the various life stages, and (3) relatively low mortality rates from predators , parasites, and diseases compared to the growth rate of the bloom former (Kremer 2001). These simultaneous environmental conditions may enable these pelagic pulses to develop over a relatively short period (i.e., days to weeks). In general, blooming species have several specific properties: wide food spectrum, high ingestion rates, rapid population growth rate , and life stages competitive with those of other species (Dawson and Hamner 2009).

Box 1 How to Define a Medusozoan Population ?

In ecology, the term population has been defined in different manners according to the authors and their research goals. Whereas some authors consider a population simply as a group of organisms of the same species that coexist in a given area, others add to this concept the condition of self-sustainability (Sinclair 1988). In other words, while the members of a population are able to exchange genes, those which belong to different populations are not able to do so (Jummars 1993).

In population ecology, the emerging characteristics of the populations are studied (e.g., abundance, spatial distribution, sex ratio, mortality and birth rates, size structure) (Begon et al. 1988). In turn, population dynamic focuses on the variations through time of the abovementioned features, the factors which cause these variations, and the mechanisms by which they occur (Ricklefs 1979). Thus, the first thing a researcher should do when studying the population ecology of a particular species is to clearly define which the population under study is and which area it occupies. This decision, although sometimes fairly trivial, presents certain complications in the study of medusozoan populations which may reflect that these ecological concepts have been thought to species (mostly terrestrial) with rather different life cycles.

The first complication emerges from the metagenetic life cycle typical of most medusozoans. The alternation between sexually reproducing planktonic stages (medusae) and asexually reproducing benthic stages (polyps) poses the following questions: What is a jellyfish population? Does it include the medusa and polyp stages? Is there a medusa population and a separate polyp population?. Considering that a given population has to be able to self-sustain, we can state the existence of a population of polyps, which can perpetuate themselves through asexual reproduction. Conversely, we cannot consider only the medusae as a population since they need the polyps to perpetuate themselves. If genetic interchange must exist within a population, we should include both medusae and polyps in the concept of population, with medusae reproducing sexually and polyps propagating asexually, ensuring the perpetuation of the species.

These events have been classified according to the observed patterns and their likely causes categorized as accumulations, mass occurrences, aggregations, swarms, population outbreaks, and blooms (true or apparent) (see Box 2.2 in Lucas and Dawson 2014). Unfortunately, in most cases they have been referred to in the literature simply as “jellyfish blooms” for reasons of simplicity, ignorance, lack of proper classification, and lack of historical records over long-term time series. Considering their individual size and the frequency and magnitude of their “blooms,” it can be said that medusozoans are the most conspicuous components of the planktonic community. For phylogenetic, ecological, and socioeconomic reasons, these phenomena have gained increased attention during the last two or three decades, with funds available for study of the causes and mechanisms of jellyfish blooms and for the development of management and adaptation strategies (e.g., Purcell 2009; Lucas et al. 2014).

There are two main ways in which medusozoans form their “blooms”: through qualitative adjustments of their life cycle or through quantitative fluctuations in the life history (Giangrande et al. 1994; Boero et al. 2008). Whereas life cycle adjustments are related to the biology and reproductive strategies (e.g., how many stages are involved?, free-living or sessile?, benthic or planktonic?, sexual or asexual?), life history adjustments deal with ecological aspects of growth and reproduction . For example, at what age and size should reproduction start? Should it be once or more than once? Should it be continuous or seasonal? How much energy and time should be allocated to reproduction? (Stearns 1992). Therefore, the evolution of life cycles and life history traits determines the population dynamics of species including the timing and magnitude of jellyfish blooms. Hence, the abundance of the medusa stage will be determined by the “success” of each part of the life cycle defined, in turn, by their interaction with the environment, including both biotic and abiotic factors. Therefore, in the metagenetic life cycle, the potential number of medusae forming a bloom will depend on fertilization rates, the ability of the planulae to settle and metamorphose, the polyp survival, and their capacity to produce medusae and medusa growth, reproduction, and survival. Jellyfish species persist locally at different times during the different life cycle stages that inhabit different environments (e.g., benthic polyps and pelagic medusae). Life cycle adjustments are, therefore, the outcome of the evolution of life cycle stages; life history adjustments are, instead, the outcome of the population dynamics (Boero 2013). In this case, species may undergo seasonal or irregular peaks of rarity and abundance in their populations through growth and reproduction of their stages (Boero et al. 2008).

In several species the presence of resting stages (i.e., cysts) adds another source of variability in later medusa abundance. Under particular (species-dependent) environmental conditions, polyps (or planulae) form (or transform into) cysts that are thought to withstand unfavorable environmental conditions (see Schiariti et al. 2014, 2015). Particular environmental stimuli (also species-dependent and poorly studied) trigger encystment, later originating new batches of polyps that, in turn, grow and reproduce leading to population peaks of the medusa stage. Those can be more intense than usual and are frequently considered to be jellyfish blooms (Arai 2009; Kawahara et al. 2013; Schiariti et al. 2014).

Trying to understand how the environment defines the timing and magnitude of jellyfish blooms and how these environmental changes potentially affect marine ecosystem functioning is impossible without a basic knowledge of the life cycles and life history of the species in question. In 2001, Mills commented that “Knowledge about the ecology of both the medusa and the polyp phases of each life cycle is necessary if we aim to understand the true causes of these increases and decreases, but in most cases where changes in medusa populations have been recognized, we know nothing about the field ecology of the polyps.” Over the past two decades, this knowledge gap has started to be addressed. The percentage of described life cycles at present reaches 40% for Cubozoa (2 described life cycles for 5 reported species) and 60% for Scyphozoa (12 life cycles for 20 reported species/morphotypes) (Table 1). In Hydrozoa, descriptions of entire life cycles remain unknown for most species. However, for many of them, there are morphological descriptions of both phases of the cycle, gonophores in the polyp and the mature medusa or description of cormidia (i.e., a cluster of zooids usually consisting of a helmet-shaped bract, a gastrozooid, and one or more gonophores) in calycophoran colonies. Consequently, it is possible to provide a general scheme of the type of life cycle for these species. Besides, if the life cycle of a certain species is known, it could be assumed that cogeneric species have a similar life cycle (e.g., Podocoryna, Clytia, Bougainvillia). Reproductive modes seem to be similar for species belonging to the order Trachymedusae (holoplanktonic, with larva stages directly developing into medusa in water column) or Narcomedusae (holoplanktonic, with larva stage parasitizing other medusa species; see comments in Section 2). Taking this into account, we can infer the reproductive way of most Hydrozoa species (7186%, 191 life cycles for 222 confirmed species) in the SWA (Table 1). However, studies about life history traits and population dynamics of key species in the SWA are still very few and urgently needed.

4 Ecological Roles of Medusozoans in Marine Ecosystems

Historically kept on the dark side of the marine ecology and ignored during traditional oceanographic cruises, medusozoans are now acknowledged as crucially modulating the dynamics of marine ecosystems. They can not only act in trophic webs as predators and prey, but they play important roles related to nutrient cycling and also establish a variety of interspecific associations that cannot be neglected. In this section, a brief review of the different ecological roles that medusozoans can play is given, focusing on the examples reported for the SWA.

4.1 Trophic Interactions

4.1.1 Medusozoans as Predators

The role of jellyfish as predators is probably the best documented among their potentially important ecological roles (Arai 2005 and references therein). Medusae and siphonophores have been tagged as “deadly creatures” by journalists and researchers (Mackie 2002; Doyle et al. 2014) and categorized as the most important predators of the sea (Pauly et al. 2009). This trend for attention on medusozoans as predators is owed to their capacity to prey on early life stages (eggs, larvae, and juveniles) of valuable fishing resources and/or to compete with them for food resources (e.g., Brodeur et al. 2002; Lynam et al. 2005).

Medusozoans display a vast diversity of feeding mechanisms and body sizes, allowing them to feed on a large range of prey types and sizes, from micro- to macroplankton (e.g., Arai 2005; Boero 2013). Most medusozoans are generalist carnivorous and prey on a variety of zooplankton, including crustaceans (small adults and larvae), fish eggs and larvae, other jellyfish (including ctenophores), and chaetognaths, among others. However, there are also specialists, some reported from the SWA, like the siphonophore Hippopodius hippopus that feeds exclusively on ostracods (Purcell 1981). Their considerable functional diversity requires more detailed information for better understanding of the roles of medusozoan in pelagic trophic webs.

Jellyfish feeding strategies (e.g., ambush, cruising predator) and characteristics of their cnidomes are related to capture of distinct prey (e.g., Purcell 1997; Costello et al. 2008). Among the hydromedusae, feeding habits are diverse, with a few species feeding on bacterioplankton and protozoans (Colin et al. 2005; Boero et al. 2007), while others feed preferentially on gelatinous prey (Larson et al. 1989; Purcell 1997), crustaceans, or fish (Zamponi and Mianzan 1985). Scyphomedusae have broader diets, including crustaceans (e.g., copepods, cladocerans, ostracods), soft-bodied animals (e.g., eggs, fish larvae, ctenophores, small hydromedusae ), and meroplanktonic larvae (bivalve veligers) (Suchman et al. 2008; Riascos et al. 2014). There are also some scyphozoans (especially in the order Rhizostomeae) that can consume both micro- and mesozooplankton (Larson 1987; Fancett 1988; Nagata 2015), which are retained along their complex oral arms (Nagata et al. 2016). In cubomedusae, age-specific diets are probably related to the maturation of their toxins and to an ontogenetic shift in their cnidome. These jellyfish generally feed on crustaceans at smaller stages, while adults can consume fish (Carrette et al. 2002; Nogueira Jr and Haddad 2008; Kingsford and Mooney 2014).

When jellyfish occur at high densities, they can remove a considerable fraction of zooplankton standing stock (ca. 20–60%) (e.g., Behrends and Schneider 1995; Purcell 2001; Uye and Shimauchi 2005). High predation impacts have been reported for scyphomedusae (Aurelia and Chrysaora: Hayet al. 1990; Purcell et al. 1994; Mills 1995; Purcell 2003; Hansson et al. 2005) and some large hydromedusae (Aequorea: Purcell and Grover 1990; Purcell 2003). Smaller species (<2 cm), such as Liriope tetraphylla and Muggiaea atlantica, may also consume large fractions of zooplankton when they occur in extremely high densities (>500 org m−3) (Greve 1994; Yilmaz 2014).

Studies about diet and feeding strategies of medusozoans from the SWA are mostly recent and restricted to laboratory observations and lists of prey items found in their gastric cavities. The prey of several medusozoans have been described in the SWA, including dinoflagellates (Noctiluca sp.), chaetognaths, barnacle larvae, cladocerans, copepods, appendicularians, other jellyfish, fish eggs, and larvae and other medusozoan species (Zamponi 1985; Zamponi and Mianzan 1985; Nagata 2015; Carrizo et al. 2016; Díaz Briz unpublished data, Dutto pers. obs.). A further and more detailed examination of gut contents, as well as diet analyses using stable isotopes, is needed to assess the impacts of medusozoans on local food web dynamics within the SWA.

4.1.2 Medusozoans as Prey

Whereas the significance of jellyfish as predators is widely acknowledged, their role as prey has been less studied. Jellyfish have been historically considered as trophic “dead ends” in marine food webs, because of their absence from gut-content analyses and their supposedly low nutritional value. They were assumed to be insufficiently nutritious to supply the energetic demands of the vertebrates preying on them (Verity and Smetacek 1996; Richardson et al. 2009). However, there is considerable evidence now indicating that a wide range of taxa consume exclusively, or opportunistically, different medusan species. There are also some reports demonstrating that polyps are consumed by a variety of predators.

Predation upon jellyfish has been reviewed on several occasions (e.g., Arai 1988, 2005; Ates 1988; Purcell 1997; Acuña et al. 2011). In these reviews, consumption of different medusan species by other jellyfish, mollusks, arthropods, fish, reptiles, and birds has been documented. Observation of intraguild predation in the SWA includes only a laboratory observation of Aurelia and Chrysaora ephyrae being eaten by the rhizostome Lychnorhiza lucerna (Carrizo et al. 2016). Although in situ local observations are lacking from the SWA, there are reports in the literature from other regions that involve species occurring in our study area, such as Aequorea feeding on several smaller hydromedusan species (Purcell 1991).

While reports of intraguild predation are few worldwide, examples of other taxa consuming jellyfish are much more common. Jellyfish comprise the diet of more than 120 fish species, 39 of them reported for the SWA (Arai 2005; Pauly et al. 2009; Díaz Briz et al. 2017), several seabirds (Harrison 1984; McInnes et al. 2017; Phillips et al. 2017; Thiebot et al. 2017), and some marine turtles (Houghton et al. 2006; Gonzalez Carman et al. 2013). Examples of medusae as prey in the SWA exist for Argentina and Uruguay, which are recorded in the historical database built by the National Institute for Fishery Research and Development of Argentina (INIDEP). This database contains results from more than 100 fish gut-content analyses (see Díaz Briz 2014).

The leatherback turtle Dermochelys coriacea and the green sea turtle Chelonia mydas represent other vertebrates that feed on jellyfish in the SWA. These two species of sea turtles are present each summer in the Río de la Plata estuary (Argentina-Uruguay), coinciding with blooms of Lychnorhiza lucerna, Chrysaora lactea, and Liriope tetraphylla (Estrades et al. 2007; Gonzalez Carman et al. 2013). During recent years, the miniaturized animal-borne video data loggers have enabled feeding events to be monitored from a predator’s perspective. Video recordings obtained from cameras placed on four penguin species revealed that Magellanic penguins (Spheniscus magellanicus) consume jellyfish (likely Chrysaora plocamia and Aequorea forskalea), particularly along the Patagonian shelf (Thiebot et al. 2017). Contributions of jellyfish to the diets of different marine vertebrate species are common, likely more so than previously thought, supporting a potentially important role of medusozoans in transferring energy within marine trophic webs.

4.2 Nontrophic Interactions

Pelagic stages of medusozoans have a broad range of potentially important ecological roles in addition to their trophic interactions (Fig. 2). These include diverse interspecific associations that have been classified under terms like phoresy, parasitism, parasitoidism, kleptoparasitism, ectocommenalism, endocommensalism, amensalism, mutualism, micropredation, and epizoism (see Towanda and Thuesen 2006; Ohtsuka et al. 2009; Chiaverano et al. 2015). Although these categorizations have mostly been vaguely defined (see Sal Moyano et al. 2012), we briefly describe these interactions that suggest keystone status in marine ecosystems, particularly from the SWA.
Fig. 2

Schematic representation of the different interspecific relationships among medusozoan and other species. Scyphomedusae with associated fishes (a), with symbiont crabs (b), with hyperiid parasites (c), and predation by fishes (d). Cubomedusae with isopod parasites (e). Hydromedusae with sea anemone parasites (f), secondary hosts in the life cycle of digenean (g), and with Narcomedusae parasites (h)

Medusae can provide structures in the water column that may be used as shelter or as focus for aggregation (Ohtsuka et al. 2009; Sal Moyano et al. 2012). A simple example is the widely documented presence of schools of small fish around the conspicuous oral arms of scyphomedusae and siphonophore colonies (Fig. 2) (Purcell and Arai 2001). The nature of these associations may change as the fish grow, but in all reported cases, large adult medusae were involved. It seems likely the fish near a medusa gain protection from predators (Mansueti 1963; Purcell and Arai 2001). However, as they grow they may consume parts of it and may steal its food. Fish survive contact with these “toxic” hosts due to a variety of special characteristics (reviewed in Arai 1988). In the SWA (particularly in Brazil), different fish species (Carangidae and Serranidae) have been observed in association with the semaeostome Chrysaora lactea and the rhizostomes Lychnorhiza lucerna and Phyllorhiza punctata (Morandini 2003; Bonaldo et al. 2004; Sobolewski et al. 2017). Several unidentified fish species have been documented in association with C. lactea and L. lucerna in the Río de la Plata estuary (Argentina-Uruguay) and with Chrysaora plocamia off Patagonia (Argentina) (Mianzan et al. 2014; Schiariti pers. obs.).

Other species, including crabs and shrimp , apparently benefit from association with medusae (Fig. 2). Brachyuran crabs riding scyphomedusae have been widely documented in coastal and estuarine environments from Brazil, Uruguay, and Argentina. In general, crabs are thought to benefit from shelter, from enhanced mobility, from access to food, and in some cases by preying on medusae (see Sal Moyano et al. 2012 and references therein). Larval, juvenile, and adult crabs all occur with medusae, suggesting varied benefits to each of the life stages. Benefits of the associations have rarely been noted for medusae, but neither is there conspicuous damage produced by crabs. The benefits obtained by crabs may be diverse , but in most cases they are only based on speculations. However, findings like that of recently molted megalopae of Libinia crabs (L. spinosa and L. ferreirae) associated with L. lucerna indicate that the crabs gain protection from their host during their most vulnerable periods. Several other associations between crabs, shrimp, and scyphomedusae have been documented in the SWA, always suggesting benefits for the symbionts with neither discernible benefits nor damages to the medusan host (Moreira 1961; Chace 1969; Mianzan et al. 1988; Nogueira Jr and Haddad 2005; Martinelli Filho et al. 2008; Santos et al. 2008; Schiariti et al. 2012; Gonçalves et al. 2016).

A different kind of association is found between medusae and hyperiid amphipods (Fig. 2). These associations reported worldwide have been considered clearly parasitic, because they are nearly always detrimental to the host, which is devoured when the hyperiid reaches adulthood (Laval 1980; Gasca et al. 2015). Adult hyperiid females may also deposit their offspring directly into the tissue of their host, which then feed on prey caught by the host or directly on the host, consuming it partially or totally (Laval 1980; Sullivan and Kremer 2011). Thus, medusae provide not only food but a reproductive habitat for some hyperiid species (Dittrich 1988). Energy from medusae may be channeled into fishes that feed on these amphipod parasites (Riascos et al. 2012). In the SWA, some cases have been recorded encompassing Hyperia galba and the scyphozoan Desmonema gaudichaudi (as D. chierchianum) (Mianzan 1986), between Brachyscelus rapacoides and C. lactea, or the hydromedusa Olindias sambaquiensis (Puente Tapia et al. submitted).

Platyhelminthes also form parasitic associations with medusozoan pelagic stages. Digenean worms, such as Monascus and Opechona, have medusae and ctenophores as secondary hosts (Fig. 2). Their transmission to fish, in which they complete their life cycles, occurs when fish consume the gelatinous zooplankton, and several examples are reported from the SWA (see Díaz Briz et al. 2012, 2015 and references therein). Four taxa of digenean metacercariae (Monascus filiformis, Opechona sp., Bacciger sp., and species of Hemiuridae) have been found parasitizing more than 20 hydromedusae and 4 scyphomedusae species (Morandini et al. 2005; Díaz Briz et al. 2012; Nogueira Jr et al. 2013, 2015).

A few studies have shown parasitic associations between medusae and isopods, and some examples have been found in the region. Isopods can affect the reproductive performance and growth of their hosts by feeding on them (Fig. 2). The isopods have been found on different parts of medusae, including the sub- and exumbrella , manubrium, oral arms, and subgenital cavities (Nogueira Jr and Silva 2005). They may use medusae as food, protection, and probably transportation (Saito et al. 2002; Nogueira Jr and Silva 2005). Several examples of these associations have been reported for the SWA, including between L. lucerna and Synidotea marplatensis, C. lactea and the isopods Cymothoa catarinensis and S. marplatensis (Nogueira Jr and Silva 2005), P. punctata and an identified Cymothoidae species (Moreira 1961), the cubozoan Chiropsalmus quadrumanus and the isopods Nerocila fluviatilis and Ancinus brasiliensis and the hydromedusa Olindias sambaquiensis parasitized by the isopod S. marplatensis (Nogueira Jr and Silva 2005).

Medusozoans can also act as parasites; for example, the actinula larva of two genera of narcomedusae (Cunina and Pegantha) settles onto hydro- and scyphomedusae establishing parasitic associations (Fig. 2). These larval stages develop into a polypoid stage using their hosts as a substrate in the pelagic realm (Bouillon 1987; Osborn 2000). In the SWA, the polypoid phase of Cunina octonaria was observed parasitizing the Trachymedusae L. tetraphylla (Puente Tapia pers. obs.), but further studies are needed for a proper characterization of this association. Another type of parasitic relationship involving non-medusozoan cnidarians involves the larvae of anemones (Spaulding 1972; Sullivan and Kremer 2011). In our region, larvae of Peachia sp. have been observed attached to the scyphomedusae C. lactea and C. plocamia (identified as C. hysoscella) (Mianzan 1986) and the hydromedusae L. tetraphylla and Eucheilota ventricularis (Puente Tapia unpubl. data.).

4.3 Nutrient Cycling

Medusozoans may contribute to support primary production (Pitt et al. 2009). The products generated by medusan excretion (C, N, and P), mucus production, and “sloppy feeding” can be significant (Pitt et al. 2005; West et al. 2009). In a similar way, regenerated products released by medusae become available to bacteria and can create the so-called jelly loop of carbon cycling between jellyfish, bacteria, heterotrophic nanoflagellates, and ciliates (Condon et al. 2011). Jellyfish may contribute to nutrient recycling through the transport of nutrients and other dissolved matter across physicochemical boundaries. Considering the abundance of some medusozoans and the scale of their diel vertical migrations (e.g., Periphylla periphylla, siphonophores), such mixing can impact ecosystem function (Doyle et al. 2014). The input of organic material to benthic and pelagic trophic webs when medusae die constitutes another nutrient flow in coastal marine environments.

Depending on their sinking speeds and water depth, jellyfish bodies may decompose within the water column or near the bottom. The decay of jellyfish may involve both leaching of dissolved organic carbon (DOC) from the medusae and mineralization by bacteria. The release of DOC during decomposition may support bacterioplankton production (Pitt et al. 2009). Decomposition of jellyfish is also likely to affect oxygen dynamics. The complete oxidation of jellyfish tissues would require considerable oxygen, resulting in local hypoxia when the decomposing biomass is large enough. The consumption of oxygen may be more severe in the benthos leading to potential anoxia. This would be particularly intense in closed areas or with slow mixing of the water. The declines and decomposition of jellyfish blooms could induce “boom and bust” dynamics in a given ecosystem. Decay of bloom abundances can even annihilate benthic fauna (e.g., Pitt et al. 2009).

5 Medusozoans and Homo sapiens

While jellyfish are some of the most ancient multicellular organisms on Earth, man only started to take notice of their impact on human activities from about the 1960s. For the general public, jellyfish are largely synonymous with stinging. However, when abundant, jellyfish can negatively affect human enterprise in a number of ways beyond the economic losses caused to the tourism industry (Lucas et al. 2014). In some regions of the world, jellyfish blooms can have substantial impacts on human activities, including the clogging of fishing nets and cooling water intakes in power plants, and damage to aquaculture systems (Purcell et al. 2007; Boero 2013). Given these sometimes dramatic consequences, the number of reports has increased, and the public has acquired an overwhelmingly negative perception of these creatures (e.g., Vandendriessche et al. 2013; Graham et al. 2014). However, as research and knowledge increase, jellyfish are also being portrayed in a more positive light. From the study of marine ecosystem functioning and biodiversity to their importance as ecosystem services providers and through the discovery of their potential economic value as food or as source of biochemical compounds, it is now clear that there is far more to jellyfish than bad news (Doyle et al. 2014). In the following section, we briefly review the variety of negative and positive interactions between medusozoans and Homo sapiens, focusing on species present in the SWA.

5.1 Medusozoans as “Troublesome” Species

5.1.1 Public Health and Tourism

Problems for tourism generated by stinging species are perhaps the most “attractive” to public media, as suggested by frequent headlines around the world. Globally, nearly 100 species have been recognized as threats to human health, a few of those being fatal (Burnett 1991). In the SWA, several medusozoans do give nasty stings, but none of those have caused fatalities so far. In general, the most serious effect is panic; clinical records are scarce, and species have not been clearly identified because few people are able to identify them with certainty. The widely distributed “Portuguese man-of-war” (Physalia physalis) is probably the most dangerous species in the region. Fortunately, although serious, injuries from it (which typically include ulceration, local muscle contractures, and tissue necrosis) are not frequent (Freitas et al. 1995; Haddad Jr et al. 2002; Failla Siquier pers. com.).

The hydrozoan Olindias sambaquiensis is one of the most frequently reported species as causing health problems (malaise, vomiting, dyspnea, and tachycardia) for swimmers off Brazil, Uruguay, and Argentina (Kokelj et al. 1993; Chiaverano et al. 2004; Haddad Jr 2008; Resgalla Jr et al. 2011; Mosovich and Young 2012). In coastal environments, Liriope tetraphylla, locally known as “tapioca,” is another hydromedusa that can be troublesome during summer because of their intense blooms (Mianzan et al. 2000; Dutto et al. 2017).

Some frequent and abundant scyphozoans can become problematic when blooming off different regions of Brazil, Uruguay, and Argentina. In southern Brazil, the larva of Linuche unguiculata has been responsible for the “sea bather’s eruption,” a pruritic erythematous papular eruption that develops in areas covered by swimsuits (Haddad Jr et al. 2001, 2010; Rossetto et al. 2015). From other regions of the SWA, erythematous lesions due to the sting of Chrysaora lactea have also been reported (Marques et al. 2014).

Box jellyfish (Cubozoa) are among the most toxic marine animals because their venom contains hemolytic, neurotoxic, and cardiotoxic elements . Along the tropical coasts of Brazil, two species have been responsible for a few reported cases: Tamoya haplonema and Chiropsalmus quadrumanus . These medusae cause an intense pain and long linear plaques (Haddad Jr 2003; Haddad Jr et al. 2002, 2009). Although it is present also in Uruguayan coasts , no accidents related to this species have been documented (Leoni et al. 2016).

Literature on the treatment of jellyfish envenomation is abundant but usually controversial and lacking scientific support. No universal therapeutic remedy exists. Thus, development species- or genus-specific therapies are needed, since the nature of the venom is organism-dependent (see Montgomery et al. 2016). Many anecdotal treatments are available (gas oil, onion, and pee are among the most surprising), but species-specific first aid response is essential for an effective treatment. The removal of tentacles followed by treatment of the stung area can be crucial to avoid further release of nematocysts. Freshwater should never be used as a treatment for jellyfish stings, because changes in osmotic concentration can trigger nematocyst release. Vinegar and seawater have been established to be an effective painkiller, and baking soda slurry can be used, both as an immediate therapy and to wash off tentacles (Mianzan et al. 2001). The training of lifeguards and education on jellyfish envenomation are strongly recommended.

5.1.2 Fisheries

Medusozoans and fisheries interact in a number of ways: (1) jellyfish feed on the eggs and larvae of the species we commercially exploit (e.g., fish, crustaceans, mollusks); (2) they are competitors with zooplanktivorous fish for food resources; (3) they can transmit parasites and bacterial pathogens to fish (Purcell and Arai 2001; Delannoy et al. 2011). Although these interactions have been documented, the majority of the cases are just speculations based on logical assumptions or literature records of similar species from other regions. The economic costs associated with these ecological interactions are very difficult to evaluate. Particularly for the SWA , we are not in a position to assess the extent of impacts that jellyfish may be having on the fishing industry (directly or indirectly). There is no reliable evidence of these interactions in the SWA, and research on medusan feeding strategies, diet, and impacts on zooplankton, ichthyoplankton, and fish communities remain relatively unknown (but see Schiariti et al. 2012, 2015; Nagata 2015; Macchi and Schiariti 2016; Nagata et al. 2016). In addition, characterization of the zooplankton community in spawning areas of the commercially important species is still not adequate to test hypotheses regarding jellyfish impacts in the region.

In addition to the potential negative effects of jellyfish on fish stocks (through their impact on recruitment rates), mass occurrences of medusae can directly affect net-based fisheries through clogging and bursting of nets, decreasing fish catch, killing and spoiling the targeted species, costing time and effort during the removal of jellyfish bycatch, and even causing fishing boats to capsize (Lucas et al. 2014 and references therein). These problems have been reported in several regions of the world but have seldom been quantified. The impact of large jellyfish blooms, such as those of Nemopilema nomurai in Japan and Phyllorhiza punctata in the Gulf of Mexico, is among the best studied cases with economic losses of several million dollars (Graham et al. 2003; Uye 2008). In South America , a few specific cases have been reported from Brazil and Argentina that were caused by year-round blooms of the large (20–30 cm bell diameter) medusa Lychnorhiza lucerna, which reduce total fish captures and catch quality, damage nets, and prevent fishermen from operating (Schiariti 2008; Schiariti et al. 2008; Nagata et al. 2009). Although blooms of C. lactea are also frequent and intense in the same regions, no impacts of this species on fishing operations have yet been documented. To a lesser extent, large catches of Desmonema gaudichaudi have interfered fishing operations off Southern Argentina (Schiariti unpubl. data).

5.1.3 Aquaculture, Power Plants and Ship Operations

The problems caused by jellyfish blooms for aquaculture, ship operations, and power plants have been reviewed by Purcell et al. (2013) and Lucas et al. (2014). In general, damage occurs for aquaculture operations when massive numbers of medusae are transported by tidal currents and accumulate around the fish cages (Doyle et al. 2008; Mianzan et al. 2014). Damage to fish may be indirect, through hypoxia, or direct by stinging as medusae or pieces passing through the mesh of the cages (Mitchell et al. 2012; Mianzan et al. 2014). Also, damaged gills may become infected by fish pathogens (Delannoy et al. 2011).

Power stations and desalination plants are located in coastal regions worldwide, because of the large amounts of cooling water needed for condensers and of seawater for desalination. Large quantities of medusae can block the screened intakes, preventing the water inflow (Purcell et al. 2007). Provision of power and desalinated water to customers can be reduced or temporarily halted altogether. A study by the Association of Nuclear Operators reported in 2006 that 44 power outages and load reductions have occurred during medusa blooms at nuclear plants (Lucas et al. 2014), but none of those were in the SWA region. Similarly to power stations, many ship operations are affected by the accumulation of jellyfish in on their cooling water uptake screens . There again, the reports of this problem in the SWA are poorly documented.

5.2 Medusozoans as “Beneficial” Species

The benefits that can be obtained from jellyfish have been obscured. However, several wealthy industries are based on particular medusan species, including their utilization as human food, as partial feedstocks for a variety of animals (e.g., fish, farmed chickens, and pigs), and as sources of biochemical compounds utilized in pharmacology and medical research (Hsieh and Rudloe 1994; Kingsford et al. 2000; Brotz et al. 2017). However, as clearly stated by Doyle et al. (2014), “the benefits of particular species for society are often more cryptic and emerge from research rather than commerce.” Paradoxically, research (number of papers and specific funding) has been growing during the last two decades, much of it in response to the problems generated by jellyfish blooms. Therefore, favored by the pressure from “bad press,” our knowledge about gelatinous species among which medusozoans are included has remarkably improved. Consequently, general acknowledgment of the ecological importance of jellyfish in marine ecosystems has developed, not only within the small jellyfish scientific community but also among fishery biologists, modelers, policymakers, businessmen, and the general public.

Medusozoan fisheries (primarily for scyphomedusae) have a long history in Asia, where jellyfish have been caught and processed as food for centuries. More recently, jellyfish fisheries have expanded to the Western Hemisphere, often driven by demand from Asian buyers and by collapse of more traditional local fish stocks. As many as 35 species of jellyfish have reportedly been consumed by humans, with the majority of commercial jellyfish fisheries focusing on species from the scyphozoan order Rhizostomeae (see Table 2 in Brotz et al. 2017). The Chinese savor jellyfish as cuisine to be served regularly, as well as for holidays, weddings, and celebrations (Hsieh and Rudloe 1994). Consumption of jellyfish is popular in other Asian countries, including Japan, Malaysia, Korea, Taiwan, and Singapore, sustaining strong market demand (Kingsford et al. 2000; Hsieh et al. 2001; Omori and Nakano 2001). Comprehensive reviews of jellyfish fisheries have been published recently describing fishing and processing techniques, diversity of targeted species, the edible products, and other uses of jellyfish (Kingsford et al. 2000; Hsieh et al. 2001; Omori and Nakano 2001; Brotz and Pauly 2017; Brotz et al. 2017). Therefore, we only describe here the main features of this industry focusing on the few ongoing local experiences.

Chinese emigrants likely first introduced jellyfish fisheries to Southeast Asia, initiating them to several countries (Brotz et al. 2017). To keep up with demand, jellyfish fisheries have spread to the Western Hemisphere, often preceded by local collapses of more traditional finfish and shrimps resources. While development of jellyfish fisheries has been explored in more than 20 Western Hemisphere countries , the degree to which they have successfully established varies (see Brotz and Pauly 2017). Most consumption continues to be in Asia, with the majority of the traded product being exported to China, Japan, and South Korea (Huang 1986, 1988; Hsieh and Rudloe 1994; Omori and Nakano 2001; Kitamura and Omori 2010). At present, catches of jellyfish as food for humans are significant, with global landings only recently exceeding 1 million tonnes (Brotz and Pauly 2017).

Jellyfish fisheries in the SWA are currently under consideration only in Argentina, targeting the rhizostome Lychnorhiza lucerna (Fig. 3) (Schiariti and Mianzan 2013; Brotz et al. 2017). To date, the life history and population dynamics of this species have been studied, as well as the development of the processed product and evaluation of the potential markets (Schiariti 2008; Schiariti and Mianzan 2013; Schiariti et al. 2015). Processing of jellyfish has been performed by fisheries researchers under instruction from potential buyers, and initial responses from Chinese and Malaysian importers have been positive. However, a major hurdle to the establishment of a permanent jellyfish fishery in Argentina is uncertainty regarding how much jellyfish can be produced from the region on a consistent basis, as buyers require a minimum availability to remain involved (Brotz et al. 2017). Significant investment is required to undertake proper biomass assessment, to investigate the costs involved, and to acquire a better understanding of jellyfish population dynamics in the region. Policymakers in the area continue to approach a potential jellyfish fishery with incredulity and are dismissive about jellyfish providing significant economic value . Conversely, fishermen in the region are motivated and have been working directly with fisheries researchers and potential buyers for several years. Until the economic and ecologic knowledge gaps can be filled, a jellyfish fishery in Argentina will remain undeveloped. Lychnorhiza lucerna also occurs along the neighboring coasts of southern Brazil and Uruguay , as shown by bycatch records and scientific studies (Schiariti 2008; Nagata et al. 2009; Schroeder et al. 2014), suggesting that the area of potential exploitation for this species can be expanded.
Fig. 3

Development of a jellyfish fishery in Argentina targeting the rhizostome Lychnorhiza lucerna . Two different phenotypes of L. lucerna medusae with whitish or purplish-blue Margilan lobs (a, b). Captures of L. lucerna medusae in the Buenos Aires Province, Argentina (c, d). Processing (salting) stages (e, f). Processed medusae exhibited in the Chinese market in Buenos Aires (g)

Jellyfish may be targeted for a number of reasons other than as food for humans. Jellyfish have been used successfully as partial feedstock for a variety of animal’s foods in traditional and aquaculture farms (Hsieh and Rudloe 1994; Gopakumar et al. 2008; Miyajima et al. 2011; Wakabayashi et al. 2012). Jellyfish may be used as bait, as is done in Japan where parts of the giant jellyfish Nemopilema nomurai are used for sea bream fishing (Omori and Kitamura 2004). Historically, fishermen in Peru used large blooms of C. plocamia to locate leatherback sea turtles (Dermochelys coriacea), which were hunted for their meat during the 1960s, 1970s, and 1980s (Brotz et al. 2017). On the other hand, different medusa species have also been studied for their potential utilization in medical, biomedical, and pharmacological research. Among the most remarkable examples are two Nobel Prizes: one in 1913 for the discovery of anaphylaxis and another in 2008 for the discovery and development of green fluorescent protein (GFP). The processing of L. lucerna to extract collagen in Brazil is among the ongoing local examples; the extraction of collagen from other rhizostomes, to be utilized in cosmetics and pharmaceuticals, is being studied (Addad et al. 2011). One company based in France (www.javenech.com, accessed 26 June 2015) processes several tonnes of Rhizostoma pulmo caught in the Atlantic Ocean for collagen each year.

There are other uses of medusae. In design engineering their biomechanics are often mimicked due to their simple and efficient designs (Gemmell et al. 2013). Among other industrial applications, jellyfish have been successfully added to cement in Russia , which increased the mechanical strength of traditional cement by 50%, although the details are unfortunately vague (see Brotz et al. 2017). Experiments have also demonstrated that jellyfish can successfully be used as fertilizer for a variety of plants, trees, and crops (see Brotz et al. 2017 and references therein). There are even recent reports that a company in Israel has developed an absorbent and biodegradable material from jellyfish that could be used in products such as diapers and paper towels (Shamah 2014). Most of the technologies that propose to use jellyfish in medical and industrial applications are in their infancy, and it will likely be sometime before there is significant demand for jellyfish other than as food. Nonetheless, it is conceivable that jellyfish could be used in a variety of future applications , some of them under current consideration in the SWA region.

6 Concluding Remarks and Guidelines for the Future

In the SWA, jellyfish can be found across and along the shelf, as well as in the oceanic environment to seaward. As a group, they are abundant all year-round, but particular species bloom seasonally. Whereas some species can be troublesome from time to time, others have shown potential to become valuable economical fishing resources. Furthermore, beyond their positive and negative impacts on different industries, the abundances some species can reach during their blooms give them important ecological roles in the marine ecosystems. Yet, although empirical data for the region have been increasing recently, too much of our understanding remains speculative because of the scarcity of specific studies on the resident species.

The SWA extends along about 10,000 km of marine coastline from northern Brazil (ca. 4°N) to southern Argentina (ca. 56°S). Opportunities and possibilities of scientific studies vary from one subregion to another in this vast area as a result of differences in funding, availability of qualified personnel, equipment, and several intricacies of the countries. The distribution of funds and research effort (hence, advances of knowledge) are heterogeneous according to the distribution of wealth. Brazilian states such as São Paulo, Rio de Janeiro, Paraná and Santa Catarina, the Río de la Plata estuarine zone (Argentina-Uruguay), and Buenos Aires Province coast (Argentina) are the regions where general knowledge about Medusozoa is relatively better. In contrast, the coasts of northern and northeast Brazil and southern Patagonia in Argentina are still poorly studied because of limited funds, lack of specialists, and the scarcity of collections from such regions. Moreover, the majority of the available records come from neritic environments and the upper layers of the oceanic realm. Therefore, the fauna from oceanic deep waters of the SWA remains underestimated or unevenly unknown.

There are reasons for this state of the art in jellyfish research in the SWA. In general, jellyfish research has been triggered worldwide in response to the socioeconomic problems for human enterprises caused by their blooms (Purcell et al. 2007). In the SWA, blooms of different medusa species (e.g., Lychnorhiza lucerna, Chrysaora lactea, Liriope tetraphylla, Olindias sambaquiensis) have been frequently documented at different locations; however, there have been no serious troubles documented so far (see Section 5.1). Therefore, the pressure from affected sectors and public media, which have produced funds and human resources dedicated to study of jellyfish elsewhere (e.g., Mediterranean and North Sea), is still absent in our region. A similar situation occurs in respect to knowledge needed for economic exploitation of different medusae. Research about the potential utilization of medusozoans as foods, or sources of collagen, are ongoing in the region (Section 5.2) but still at a small scale because of the lack of research funding from private or public sources. Consequently, research on medusozoans is recent and scarce and has been provided budgets too limited for field sampling or to build long-term databases. The available grants have been used to collect medusozoan specimens in particular areas for isolated periods and to improve the laboratory equipment of some institutions in Brazil, Uruguay, and Argentina. However, they have been insufficient to answer most of the questions concerning larger spatial and temporal scales and the deep details of species biology.

One of the main limitations for study of jellyfish is the limits on logistical resources (mainly ship time) available to jellyfish researchers. Therefore, alternatives must be found, and indirect sources of information from surveys not specifically for study of jellyfish, although far from ideal, can be very useful. In this context, the integration of goals and methodologies between jellyfish researchers and fishery biologists has become an interesting approach (see Pauly et al. 2009). Only when interdisciplinary research starts across in a number of SWA areas we will be in a better position to address the roles of jellyfish in marine ecosystems and their potential impacts on human activities. Some countries, like Argentina and Uruguay, organize regular fisheries resource surveys across extensive national and international waters, with many of these incidentally involving a bycatch of large jellyfish species. Although the fishing gear used is rarely suitable for accurate quantitative sampling of jellyfish (either to collect undamaged specimens for taxonomy or live specimens for experimentation), the equipment and methods are reasonably controlled, and records of such bycatch events could provide good relative indices of the distributions and abundance of large scypho- and hydromedusae (Schiariti 2008; Purcell 2009; Bastian et al. 2010; Schiariti et al. 2013; Rodriguez et al. 2017). Furthermore, over several years the data collected during these standardized surveys forms interesting time series, useful for investigating interannual variations of relative jellyfish abundances (Brodeur et al. 1999; Lynam et al. 2005; Schiariti 2008; Bastian et al. 2010). In Argentina, the National Institute for Fishery Research and Development (INIDEP) has performed routine fishery research cruises since the 1980s, cruises being utilized to build a gelatinous zooplankton database covering most of the Argentinean continental shelf (ca. 1 million km2). Demersal (mostly) and pelagic fishing trawls and a variety of plankton devices have been utilized with different aims, and several macromedusa species have been caught as bycatch (>5 cm bell diameter) (Schiariti et al. in press). Important information about the occurrence and spatial distribution of these species has been also obtained with acoustic devices (Álvarez Colombo et al. 2003; Cabreira et al. 2006).

However, the opportunities provided by fishery research surveys are not completely appropriate because their methods and sampling designs that are inadequate for study of jellyfish. The majority of the specimens are severely damaged and useless for experimentation or even taxonomic identification. Besides, jellyfish blooms of any kind might impair plankton nets or typical demersal trawling in next to no time or, if the specimens are sparse, might not be evaluated in the right way. In addition, historically jellyfish bycatch has not even been recorded on a regular basis. Most of the time, the jellyfish catch has not been recorded at all, and they were simply discarded. Therefore, this information is reliable when jellyfish blooms were recorded, but the reverse is not true. Therefore, the way that medusozoans are being studied in the SWA needs to be reevaluated, because it is mostly linked to episodic observations that can be considered as almost anecdotal. Therefore, we consider that jellyfish research in the SWA is still in its infancy.

Funding is not the only trouble for the study of jellyfish in the SWA. Key obstacles to a more widespread study of medusozoans are still the limited time to collect samples and data onboard due to the demanding workload of the fishery surveys as well as the insufficient human resources. Currently, the number of specialists in the region is too low to cover such a vast and diverse region. Indeed, few than 20 researchers from the 3 countries are dedicated to medusozoans, and the number of specialists on particular taxa is even lower, making this field potentially attractive for masters and PhD students. Solutions for these problems demand organization and financial support. We believe that training in the systematics and ecology of medusozoans and stretching the gap between researchers, fishermen, journalist, and policymakers should be a priority. Comprehensive monographs on specific groups should be undertaken, because they generate thorough and qualified results over a relatively short period. Improvement in the quality and number of collections is of utmost importance for continuity of studies, preservation of data, and availability of specimens for future comparisons (Marques et al. 2003). Given that recognition of the important ecological interactions between finfish and jellyfish populations has grown wider, we hope that it may become easier to initiate fruitful collaborations and to leverage appropriate resources.

Better understanding of medusozoan taxonomy should be the first step and will facilitate other research, such as on pharmacology, ecology, and phylogeny. The detailed description of more life cycles and the study of the life histories and population dynamics of medusozoans are also of paramount importance for understanding the ecological roles these species play in marine ecosystems and the regulation of their blooms by environmental factors. Finally, integration among jellyfish researchers, oceanographers, and fishery biologists is essential to obtaining broadscale datasets useful not only to jellyfish research but to everyone with an interest in developing a better understanding of the effects of climate and other environmental and biological factors on oceanic ecosystems. Such integration will be a critical element in development of an ecosystem-based approach to fisheries management. In addition, research outputs generated by jellyfish datasets are usually welcomed by the scientists in charge of fisheries surveys, who value them to help them justify the surveys and secure future funding. Medusozoans have become too cogently significant to be neglected.

Notes

Acknowledgments

This paper was supported by INIDEP, CONICET PIP 2013-00615, FONCyT PICT 2013-1773, and FONCYT PICT 2015-1151. ACM was supported by grants 2010/50174–7, 2011/50242–5, and 2015/21007-9 São Paulo Research Foundation (FAPESP) and by CNPq (301039/2013–5 and 304961/2016-7). This is a contribution of NP-BioMar, USP. This is INIDEP contribution N° 2119.

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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Agustín Schiariti
    • 1
    • 2
  • María S. Dutto
    • 3
  • André Carrara Morandini
    • 4
  • Renato M. Nagata
    • 5
  • Daiana Y. Pereyra
    • 1
  • Francisco A. Puente Tapia
    • 6
  • Luciana Díaz Briz
    • 6
  • Gabriel Genzano
    • 6
  1. 1.Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP)Mar del PlataArgentina
  2. 2.Instituto de Investigaciones Marinas y Costeras (IIMyC), CONICETUniversidad Nacional de Mar del PlataMar del PlataArgentina
  3. 3.Instituto Argentino de Oceanografía (IADO), Centro Científico Tecnológico Bahía Blanca, CONICET – UNSBahía BlancaArgentina
  4. 4.Departamento de Zoologia, Instituto de BiociênciasUniversidade de São Paulo (USP)São PauloBrazil
  5. 5.Instituto de Oceanografia Universidade Federal do Rio Grande (FURG) Rio GrandeRio GrandeBrazil
  6. 6.Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y NaturalesUniversidad Nacional de Mar del Plata (UNMdP)Mar del PlataArgentina

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