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Marine Biodiversity

, Volume 48, Issue 1, pp 531–544 | Cite as

First record of the deep-sea isopod family Dendrotionidae (Isopoda: Asellota) from the Northwest Pacific with description of two new species of Dendromunna

  • Olga A. Golovan
  • Marina V. Malyutina
  • Angelika Brandt
Original Paper

Abstract

Two new abyssal species of Dendrotionidae are described: Dendromunna kurilensis sp. nov. from the Northwest Pacific Basin to the east of the Kuril–Kamchatka Trench and D. okhotensis sp. nov. from the Kuril Basin of the Sea of Okhotsk. The new species represent the first records of the family for the Northwest Pacific and the first records of the genus for the North Pacific. The new species differ from the remaining species of Dendromunna by the extremely long antennae and pereopods (antenna I is about 0.7–0.8 body length, article 4 of antenna II is about 0.6–0.7 body length, bases of pereopods are about 0.2–0.3 body length), the male pereopod I with concave lateral margins, short pereonite 1 (<0.03 body length), and the lack of mandibular palp. D. okhotensis sp. nov. differs from D. kurilensis sp. nov. by the more slender body, presence of stout setae on the pereonites 1–4 ventral surface, by different number of maxilliped retinaculae, and by number of spines of the mandibular spine row. The key to the species of Dendromunna is presented.

Keywords

Isopoda Asellota Dendrotionidae Dendromunna Northwest Pacific Kuril–Kamchatka trench area Kuril Basin Sea of Okhotsk Deep sea Abyssal KuramBio SokhoBio Taxonomy New species 

Introduction

At abyssal depths, the isopod suborder Asellota is usually reported as one of the dominating macrobenthic taxa (Brandt et al. 2004, 2005, 2007a, b, c; Brenke et al. 2005; Golovan et al. 2013; Lörz et al. 2013). This is a highly diverse group with most impressive radiation in the deep sea (up to now, 23 primarily deep-sea families have been accepted) (Raupach et al. 2009; Riehl et al. 2014). Most of these families are cosmopolitan or have a wide distribution (Wilson 1998; Raupach et al. 2009; Riehl et al. 2014).

Dendrotionidae is a small family of asellotes with a peculiar morphology. Its members are reported to be commensals of sponges (Hansen 1916; George 2004). Dendrotionids are usually not frequent, however, in the abyss of the equatorial Atlantic Ocean: they were collected with rather high abundance (dozens of individuals per one C-EBS sample) in the Vema Fracture Zone (Brandt et al. 2015a). The family includes 25 described species of three genera: Dendrotion G.O. Sars, 1872 (11 species); Acanthomunna Beddard, 1886 (ten species), and Dendromunna Menzies, 1962 (four), known from the North Atlantic (ten species), the South Atlantic (two), the Antarctic (one), the South Pacific (ten) and the Northeast Pacific (one). Representatives of the family have been found at depths ranging from 130 to 6,568 m, while most species occur at bathyal depths (Schotte et al. 1995; Cohen 1998; Brandt et al. 2015a).

Within Dendrotionidae, the eye-bearing and more eurybathic and specious genus Acanthomunna Beddard, 1886 is assumed to have a basal phylogenetic position, while the eyeless deep-sea genus Dendromunna Menzies, 1962 is considered to be more derived (Wilson 1976; Raupach et al. 2009). Only two species of the family have been found on the shelf until now; both of them are eurybathic species of the genus Acanthomunna, which also occur at bathyal depths. Until now, only two dendrotionid species have been described from abyssal depths, namely Acanthomunna beddardi Menzies, 1962 from the South Atlantic (at 4885 m) and Dendromunna mirabile Wolff, 1962 from the South Pacific (Kermadec Trench, at 5,230–5,340 m) (Schotte et al. 1995; Cohen 1998). In addition, unidentified representatives of the family have been collected in the abyss of the Southern Ocean (Brandt et al. 2005, 2016), the South and North Atlantic (Martínez Arbizu et al. 2015), as well as in the hadal of the equatorial Atlantic Ocean (at depths up to 6,568 m) during the VEMA-Transit expedition (Brandt et al. 2015a). Moreover, dendrotionids have been found in the abyss of the Northwest Pacific. Thus during the German–Russian expedition KuramBio (Kurile Kamchatka Biodiversity Studies, 2012) (Elsner et al. 2015; Golovan et al. in press) in the abyssal plain to the east of the Kuril–Kamchatka Trench and the Russian–German expedition SokhoBio (Sea of Okhotsk Biodiversity Studies, 2015) in the Kuril Basin of the Sea of Okhotsk, two new species of the genus Dendromunna were collected. During these expeditions, a camera–epibenthic sledge C-EBS (Brandt et al. 2013) was used for sampling macrobenthos, and thus a much richer fauna was discovered in the Northwest Pacific than was known previously (Brandt et al. 2015b; Elsner et al. 2015). For example, in the KuramBio samples 243 species of Asellota were identified; about 90% of them were new to science (Golovan 2015a, b; Golovan et al. in press).

Within Dendrotionidae, the eye-bearing and more eurybathic and specious genus Acanthomunna Beddard, 1886 is assumed to have a basal phylogenetic position, while the eyeless deep-sea genus Dendromunna Menzies, 1962 is considered to be more derived (Wilson 1976; Raupach et al. 2009). Only two species of the family have been found on the shelf until now; both of them are eurybathic species of the genus Acanthomunna, which also occur at bathyal depths. Until now, only two dendrotionid species have been described from abyssal depths, namely Acanthomunna beddardi Menzies, 1962 from the South Atlantic (at 4885 m) and Dendromunna mirabile Wolff, 1962 from the South Pacific (Kermadec Trench, at 5,230–5,340 m) (Schotte et al. 1995; Cohen 1998). In addition, unidentified representatives of the family have been collected in the abyss of the Southern Ocean (Brandt et al. 2005, 2016), the South and North Atlantic (Martínez Arbizu et al. 2015), as well as in the hadal of the equatorial Atlantic Ocean (at depths up to 6,568 m) during the VEMA-Transit expedition (Brandt et al. 2015a). Moreover, dendrotionids have been found in the abyss of the Northwest Pacific. Thus during the German–Russian expedition KuramBio (Kurile Kamchatka Biodiversity Studies, 2012) (Elsner et al. 2015; Golovan et al. in press) in the abyssal plain to the east of the Kuril–Kamchatka Trench and the Russian–German expedition SokhoBio (Sea of Okhotsk Biodiversity Studies, 2015) in the Kuril Basin of the Sea of Okhotsk, two new species of the genus Dendromunna were collected. During these expeditions, a camera–epibenthic sledge C-EBS (Brandt et al. 2013) was used for sampling macrobenthos, and thus a much richer fauna was discovered in the Northwest Pacific than was known previously (Brandt et al. 2015b; Elsner et al. 2015). For example, in the KuramBio samples 243 species of Asellota were identified; about 90% of them were new to science (Golovan 2015a, b; Golovan et al. in press).

The only known North Pacific dendrotionid, Acanthomunna tannerensis Schultz, 1966, has been found at bathyal depth (813 m) of the Tanner Canyon, California.

The genus Dendromunna includes four species described from bathyal depths (1,271–2,550 m) of the North Atlantic (two species), South Atlantic (one species) and abyssal depths of the South Pacific (one species, Kermadec Trench, 5230–5340 m) (Menzies 1962; Wolff 1962; Lincoln and Boxshall 1983; George 2004) (Fig. 1). Except for D. compsa Lincoln and Boxshall, 1983, descriptions of all of these species are based on only one specimen. In D. spinipes Menzies, 1962 and D. mirabile Wolff, 1962, the type specimen is damaged.
Fig. 1

Distribution map of the species of Dendromunna Menzies, 1962. Type localities: 1 — D. bruuni George, 2004; 2 — D. compsa Lincoln and Boxshall, 1983; 3 — D. mirabile Wolff, 1962; 4 — D. spinipes Menzies, 1962; 5 — D. kurilensis sp. nov.; 6 — D. okhotensis sp. nov.

In the present paper, two new species of Dendromunna are described. They are the first records of the family for the Northwest Pacific and the first records of the genus for the North Pacific.

Material and methods

The material for this study was collected during the two subsequent deep-sea expeditions in the Northwest Pacific. The German–Russian expedition KuramBio (Kurile Kamchatka Biodiversity Studies) took place in July–August 2012 on board the German RV Sonne. The project aimed to study the abyssal plain adjacent to the Kuril–Kamchatka Trench (KKT) (Brandt and Malyutina 2015). The Russian–German expedition SokhoBio (Sea of Okhotsk Biodiversity Studies) in July–August 2012 on board of the RV Akademik M.A. Lavrentyev took samples in the Kurile Basin of the Sea of Okhotsk. During both expeditions, macrobenthos was sampled using a camera–epibenthic sledge C-EBS (Brandt et al. 2013, 2015b). The samples were washed onboard with cold filtered sea water immediately after hauling through sieves of 300 μm mesh size. At each station, the samples from the first deployment at each station were fixed in pre-cooled 96% ethanol. The samples from the second deployment in KuramBio were initially fixed in 4% formalin for 48 h and then re-fixed with −20 °C pre-cooled 96% ethanol, and in SokhoBio were fixed in pre-cooled 96% ethanol as well. The material was sorted using stereomicroscopes (different models) in the laboratory on board and later in the Zoological Museum of the University of Hamburg and in the Institute of Marine Biology (Vladivostok).

The best-preserved specimens of both species were designated as holotypes. Among the specimens of Dendromunna kurilensis sp. nov., the male holotype was the only specimen with pleotelson and pereopods presented. Antennae I, II, pereopods, and pleopod I were drawn from the holotype without dissection. Pleopods II-V were not studied, to avoid the destruction of pleotelson. The mouthparts and the female antennae were dissected from the female paratype.

In the description of D. okhotensis sp. nov. all appendages, except the pereopod V, were dissected from the male and female paratypes. The drawings were made using a Zeiss Discovery v.12 stereoscopic dissection microscope and Olympus CX31RTSF microscope, both equipped with a camera lucida.

The figures were illustrated using a Wacom Cintiq 22HD interactive display and processed using Adobe Photoshop CС.

The maps were generated using GeoMapApp 3.3.9.

Terminology and measurements except for body length, segments, and appendages follow Wolff (1962), Hessler (1970), and Wilson (1989, 2008). Body length was measured from the ventral views from the anterior edge of head to the posterior edge of pleotelson, because the curved shape of the described species does not allow an illustration of standard views. The lengths of the body segments were measured medially from dorsal views; widths were measured without dorsolateral spines.

The type material is deposited in the Museum of the Institute of Marine Biology (MIMB), Vladivostok, Russia and the Zoological Museum Hamburg (ZMH).

Abbreviations

Md-mandibular, SS-simple seta, BS-broom seta, UBS-unequally bifid seta

TAXONOMY

Order Isopoda Latreille, 1817

Suborder Asellota Latreille, 1803

Superfamily Janiroidea Kussakin, 1967

Family Dendrotionidae Vanhöffen, 1914

Genus Dendromunna Menzies, 1962

Dendromunna Menzies, 1962: 167. – Wolff 1962: 66. – Lincoln and Boxshall 1983: 299. – Kussakin 1988: 242. – Cohen 1998: 21. – George 2004: 56.

Type species: Dendromunna spinipes Menzies, 1962, by original designation.

Diagnosis: see Cohen 1998.

Composition: Dendromunna bruuni George, 2004; D. compsa Lincoln and Boxshall, 1983; D. kurilensis sp. nov.; D. mirabile Wolff, 1962; D. okhotensis sp. nov.; D. spinipes Menzies, 1962.

Dendromunna kurilensis sp.nov. Golovan and Malyutina.

Material examined. Holotype: (MIMB 33580) male (2.7 mm), KuramBio St.9–9-S, 40°35′29″N 150°59′55″E–40°34′15″N 150°59′55″E, 5399–5408 m; designated here.

Paratypes: (ZMH K-46576) one female with oostegites (2.8 mm without pleotelson), one female (1.3 mm without pleotelson), same data as holotype; (MIMB 33581) one female, damaged, used for dissection, St. 10–9-S, 41°12′28″N, 150°5′38″E–41°11′10″N, 150°5′36″E, 5264–5266 m.

Etymology. The species name refers to the type locality of the species.

Diagnosis. Male body length 3.7 width. Pereonites 1–7 free. Pereonite 1 length 0.02 body length. Pleotelson dorsal surface with two stout submedial setae. Antenna I about 0.8 body length, flagellum consisting of 29 articles in male and ten articles in female. Antenna II articles 1–5 together more than 1.3 times longer than body, article 4 about 0.7 body length. Mandibular palp absent, spine row of left mandible with three spines, of right mandible with seven spines. Maxilliped with one retinacula. Pereopods long: pereopod IV basis to carpus length 1.3 times longer than body, bases of pereopod I about 0.2 body length, bases of pereopods III–VI about 0.3 body length. Male pleopod I length 2.5 widths, lateral margins concave.

Description. Holotype, male: Body (Fig. 2a, b) curved, length 3.7 pereonite 3 width, body height 0.16 length.
Fig. 2

Dendromunna kurilensis sp. nov. ad Male, holotype (MIMB 33580). e, f Female, paratype. g Juvenile female, paratype (ZMH K-46576). a, e, g Dorsal view; b, f lateral view; c head, frontal view; d pleotelson, ventral view. Scale bar 1 mm

Head: length 1.0 width and 0.16 body length, widest and highest anteriorly, on level of antennal insertion.

Pereonite 1 length 0.13 width and 0.02 body length; pereonites 2–7 length in relation to pereonite 1 length: 5.8; 6.9; 6.5; 4.4; 2.7; 1.5; length–width ratios: 0.47; 0.53; 0.51; 0.48; 0.3; 0.32. Pereonites 1–4 anterolateral angles with thin acute spine. Pereonite 1 anterior and posterior margins concave. Pereonites 2–4 anteriorly and pereonites 5–6 posteriorly with lateral expansions, bearing pereopods; lateral expansions 2–6 distally with dorsolaterally directed projections ending with cluster of radial spines. Pereonites 2–3 posterior part of dorsal surface with pair of elevations, bearing a long cylindrical projection with radiate spines at the top (most projections, however, are broken off in these specimens); pereonites 4–5 with two thin acute spines in this position; pereonite 6 with two small acute dorsal spines. Pereonite 7 projected posteroventrally, with posterolateral protrusions bearing stout UBS. Coxae I–VI visible in dorsal view, coxa I with anterolateral UBS, coxa VI posteriorly with acute projection.

Pleotelson length 1.5 widths and 0.23 body length; height 0.43 length, highest mediodorsally; sharply bent down posteriorly to the base of uropodal insertion; anterior third of dorsal surface with bases of two stout setae submedially (broken); anterior half of lateral margin with two short stout UBS at both sides; posterior margin rounded, with few fine SS.

Antenna I (Fig. 3a) about 0.8 body length. Articles 1–3 length–width ratios: 2.0; 4.5; 9.7; articles 2–3 lengths in relation to article 1 length: 1.1; 2.4; article 2 with BS distally. Flagellum with 29 articles, article 1 shortest, length 2.3 width, article 2 longest, length 4.8 width, all articles bearing fine SS distally.
Fig. 3

Dendromunna kurilensis sp. nov. Male, holotype (MIMB 33580). a, b antennae I, II; c, d pereopods I, II; e pereopod IV, basis – carpus; f pereopod VI, basis. Scale bar 0.2 mm

Antenna II (Fig. 3b) articles 1–5 1.3 times longer than body, article 4 longest, about 0.7 body length, article 5 broken, flagellum lost. Articles 1–4 length-width ratios: 1.7; 1.1; 1.4; 28.0; articles 2–4 lengths in relation to article 1 length: 0.70; 0.87; 12.5; articles 1 and 2 with small UBS distally, article 4 covered with small tubercles, with about seven small and one longer UBS and one BS.

Mouthparts: see description of the female paratype.

Pereopod I (Fig. 2b, 3c) basis about 0.2 body length; ratios of lengths of basis–dactylus to their widths: 9.2; 5.2; 2.2; 11.5; 5.2; 4.0; ratios of lengths of ischium–dactylus to basis: 0.38; 0.19; 0.72; 0.23; 0.13. Merus with one distodorsal UBS; carpus with two ventral SS; propodus with one distoventral SS. Dactylus dorsal claw length 0.41 dactylus length, ventral claw about half as long as dorsal claw, two sensillae inserted between claws.

Pereopod II (Fig. 2b, 3d) basis about 0.23 body length; ratios of lengths of basis–dactylus to their widths: 9.2; 2.5; 5.0; 9.4; 6.3; 6.6; ratios of lengths of ischium–dactylus to basis: 0.23; 0.41; 0.57; 0.30; 0.19. Basis with two dorsal slender SS; merus and ischium with one ventral fine SS; carpus with four long stout ventral and one distodorsal UBS; propodus with four ventral UBS, one distoventral and one dorsal SS; dactylus with two fine SS, dorsal claw length 0.31 dactylus length.

Pereopod III (Fig. 2b) broken off, except for basis, basis about 0.31 body length.

Pereopod IV (Fig. 2b, 3e) basis to carpus length 1.3 times longer than body, basis about 0.33 body length; ratios of lengths of basis–carpus to their widths: 7.1; 2.9; 4.1; 24.0; ratios of lengths of ischium–carpus to basis: 0.38; 0.53; 2.3. Basis with stout seta ventrally (broken off in this specimen); carpus with about six short UBS ventrally and one distoventral SS.

Pereopod V broken off in this specimen.

Pereopod VI (Fig. 2b, 3f) broken off in this specimen, except for basis, basis 0.30 body length.

Pleopod I (Fig. 2d) length 2.5 widths, lateral sides concave; distomedial lobes extending 0.11 pleopod I length beyond lateral lobes, each lobe distally with few SS.

Pleopods II–V not studied.

Uropods broken off in this specimen.

Paratype, female: Pereonite 4 posterior part of dorsal surface with projections ending with cluster of radially directed spines. Pleotelson lost.

Antenna I (Fig. 4a) articles 1–3 length–width ratios: 2.4; 3.5; 20.4; articles 2–3 lengths in relation to article 1 length: 0.95; 3.0; article 1 with BS distally, article 2 with 2 BS and 1 UBS distally. Flagellum with ten articles, article 1 length 1.4 width, article 2 length 19.2 width, articles 7–10 bearing fine SS distally.
Fig. 4

Dendromunna kurilensis sp. nov. Female, paratype (MIMB 33581). a Antenna I and antenna II articles 1–4; b, c left and right mandibles; d, e maxillae 1, 2; f maxilliped; g hypopharynx. Scale bar 0.1 mm

Antenna II (Fig. 4a) articles 1–3 length–width ratios: 1.3; 0.85; 1.6; articles 2–3 lengths in relation to article 1 length: 0.65; 1.3; article 3 with two UBS distally; distal part of antenna II missing.

Mandibles (Fig. 3b, c): incisor process with four cusps on left mandible and six cusps on right mandible. Lacinia mobilis of left mandible with four cusps; spine row with three spines. Spine row of right mandible with four spines. Molar process distally with three setae. Palp absent, one SS instead of palp.

Hypopharynx (Fig. 4g) with long setae medially, medial lobe triangular.

Maxilla I (Fig. 4d) lateral endite distally with 13 robust setae, laterally and medially with few fine SS; mesial endite width 0.57 lateral endite width, distally with four robust setae.

Maxilla II (Fig. 4e) lateral endite distally with four robust setae; middle endite longest, width 0.72 lateral endite widths, distally with three robust setae; mesial endite shortest, width 1.2 lateral endite width distally with about eight fine setae.

Maxilliped (Fig. 4f) basis length 2.6 width, with one SS near palp insertion; endite length 1.4 width, 0.46 basis length, with one retinacula, distal margin with 3 fan setae, four UBS, two large and numerous fine SS. Palp article 1 width 0.37 basis width, lateral length 0.09 basis length; articles 2–5 to article 1 lateral length ratios: 1.8; 2.2; 2.3; 1.5; articles 1–5 lateral lengths to width ratios: 0.64; 1.1; 1.3; 1.7; 2.5; articles 2–3 with one and two distomedial SS respectively, articles 4–5 with three and five distal SS respectively. Epipod length 2.7 width, 0.91 basis length, narrowing distally.

Pereopods (Fig. 2f) lost, except basis; bases slightly shorter than those in male.

Remarks. D. kurilensis sp. nov. differs from D. spinipes Menzies, 1962 and D. bruuni George, 2004 by the short pereonite 1 (0.02 body length in the new species, > 0.07 body length in D. spinipes and D. bruuni). The new species differs from D. compsa Lincoln and Boxshall, 1983 and D. mirabile Wolff, 1962 by the absence of mandibular palp, long antennae and pereopods, the morphology of pleotelson, the male pleopod I with concave lateral sides. D. kurilensis sp. nov. is most similar to D. okhotensis sp. nov.; the comparison of both new species is presented below.

Type locality. Northwest Pacific to the east of the Kuril–Kamchatka Trench, from 40°35′29″N 150°59′55″E–40°34′15″N 150°59′55″E to 41°12′28″N, 150°5′38″E–41°11′10″N, 150°5′36″E, at depth ranges from 5,264 to 5,266 to 5,399–5,408 m.

Distribution. Known only from the type locality.

Dendromunna okhotensis sp.nov. Golovan and Malyutina.

Material examined. Holotype: (MIMB 33582) female (2.4 mm), SokhoBio St.7–3-S, 46°56.556 N 151°05.013E–46°56.791 N 151°04.860E, 3299 m; designated here.

Paratypes: (MIMB 33583) one male (3.0 mm), same data as holotype; (ZMH K-46577) one female, used for dissection, St.7–4-E, 46°57.466 N 151°05.068E–46°57.494 N 151°04.917E, 3,300 m.

Etymology. The species name refers to the type locality of the species.

Diagnosis. Body length 4.1 width in male and 3.8 width in female. Pereonites 1–7 free. Pereonite 1 length 0.02–0.03 body length. Pereonites 1–4 ventrally with transverse elevations bearing strong setae. Pleotelson dorsal surface near highest point with two submedial UBS. Antenna I about 0.8 body length, flagellum consists of 27 articles in male and eight articles in female. Antenna II articles 1–5 length together equal to body length, article 4 0.7 body length. Mandibular palp absent, spine row of left mandible with four spines, of right mandible with nine spines. Maxilliped with two retinaculae. Pereopods long: pereopods 5–6 2 times longer than body length; pereopods 1–6 bases about 0.2–0.3 body length. Male pleopod I length 3.0 widths, lateral sides concave. Uropod protopod length 0.72 pleotelson length, exopod longer than protopod.

Description. Holotype, female: Body (Fig. 5a, b) curved, length 3.8 pereonite 4 width, body height 0.18 length. Head: length 1.3 width and 0.20 body length, widest and highest anteriorly, under the base of antennal insertion.
Fig. 5

Dendromunna okhotensis sp. nov. Female, holotype (MIMB 33582). a Lateral view; b dorsal view; c pleotelson, ventral view; d pereopod V. Scale bar ac 1 mm; d 0.2 mm

Pereonite 1 length 0.13 width and 0.02 body length; pereonites 2–7 length in relation to pereonite 1 length: 4.8; 6.2; 6.9; 4.0; 1.9; 1.4; length–width ratios: 0.45; 0.53; 0.58; 0.35; 0.25; 0.35. Pereonite 1 anterolateral angle with thin acute spine, pereonites 2–4 with strong seta on this location. Pereonite 1 anterior and posterior margins concave. Pereonites 2–5 lateral expansions with dorsolaterally directed projections ending in a cluster of radially directed spines; pereonite 6 with bifurcated spine in this location. Pereonites 2–4 posterior part of dorsal surface with dorsally directed projections ending in a cluster of 2–4 radially directed spines, these projections smaller in size, than lateral ones. Pereonites 6 and 7 dorsally with two pairs of stout setae and a row of six stout setae respectively. Pereonite 7 projected posteroventrally, with posterolateral protrusions each bearing two stout UBS. Ventral surface of pereonites 1–4 anteriorly with transverse elevations bearing strong UBS; ventral surface of pereonites 5–7 with irregularly placed UBS. Coxae I–VI visible in dorsal view, coxa I anterolaterally, coxae V and VI posteriorly with acute projections.

Pleotelson length 1.7 widths and 0.22 body length; height 0.54 length, highest in central part, height gradually decreases posteriorly; dorsal surface near its highest point with two submedial UBS; anterior third of lateral margins with short UBS.

Antenna I (Fig. 5a) about 0.8 body length.

Antenna II (Fig. 5a) article 4 longest, about 0.6 body length, article 5 broken off, flagellum lost.

Pereopods long (Fig. 5a). Pereopods 1–3 broken off in these specimens, except basis, pereopods 1–3 basis in relation to body length: 0.19; 0.22; 0.27.

Pereopod IV (Fig. 5a) basis about 0.27 body length; ratios of lengths of ischium–propodus to basis: 0.30; 0.62; 1.8; 2.2.

Pereopod V (Fig. 5d) basis about 0.25 body length; ratios of lengths of basis–dactylus to their widths: 6.9; 3.0; 5.2; 20.8; 73.9; 27.1; ratios of lengths of ischium–dactylus to basis: 0.37; 0.65; 2.1; 3.12; 0.73; 0.10. Basis with two dorsal spine-like seta; ischium with one ventral UBS; merus with one dorsal SS; carpus with two small UBS ventrally and three long and one short UBS dorsally; propodus with one long UBS dorsally, five small UBS dorsally and six small UBS ventrally; dactylus with two fine ventral SS, claw length 0.10 dactylus length, with one sensillum.

Uropod (Fig. 5a–c) protopod length 0.72 pleotelson length, with two stout UBS on proximal half and one short and one long stout UBS distally. Endopod broken off in this specimen. Exopod broken, remaining part 1.1 protopod length, with three long UBS medially and two broken setae laterally.

Paratype, female: Antenna I (Fig. 6a) articles 1–3 length–width ratios: 1.9; 2.5; 12.8; articles 2–3 lengths in relation to article 1 length: 0.93; 2.9; articles 1 and 2 each with two BS distally. Flagellum with eight articles, article 1 length 1.3 width, article 2 length 15.7 width, article 5 with one fine SS distally, article 8 with five terminal SS.
Fig. 6

Dendromunna okhotensis sp. nov. Female, paratype (ZMH K-46577): a antenna I; b antenna II; c, d left and right mandibles; e, f maxillae 1, 2; g maxilliped. Scale bar 0.1 mm

Antenna II (Fig. 6b) articles 1–4 length-width ratios: 1.4; 0.83; 1.4; 27.1; articles 2–4 lengths in relation to article 1 length: 0.63; 1.1; 11.3; article 2 with long UBS distally, article 3 with two strong broken setae distally, article 4 covered with small tubercles and about 17 long UBS; article 5 broken, flagellum lost.

Mandibles (Fig. 6c, d): incisor process with four cusps on left mandible and six cusps on right mandible. Lacinia mobilis of left mandible with five cusps; spine row with four serrated spines. Spine row of right mandible with three weak and six robust serrated spines. Molar process distally with four setae. Palp absent, one SS instead of palp 0.15 Md body length.

Maxilla I (Fig. 6e) lateral endite distally with about 8 robust setae, laterally and medially with few fine SS; mesial endite width 0.54 lateral endite width, distally with five robust setae.

Maxilla II (Fig. 6f) lateral endite shortest, distally with four robust setae; middle endite width 1.5 lateral endite width, distally with four robust setae, medial margin with fine setae; mesial endite longest, width 1.8 lateral endite width, distal and distolateral margins with about 11 robust and numerous long fine setae.

Maxilliped (Fig. 6g) basis length 2.4 width, with one SS near palp insertion; endite length 1.3 width, 0.44 basis length, with two retinaculae, distal margin with about eight fan setae, about six large and numerous fine SS. Palp article 1 width 0.41 basis width, lateral length 0.06 basis length; articles 2–5 to article 1 lateral length ratios: 2.8; 3.0; 3.4; 2.6; articles 1–5 lateral lengths to width ratios: 0.37; 0.93; 1.0; 2.4; 2.1, article 1 with 1 medial SS, article 2 medially with track of seta insertion, articles 3–5 with 4, 1 and 5 distal SS respectively. Epipod length 3.3 width, equal to basis length, narrowing distally.

Operculum (Fig. 7a) length 1.5 width; lateral sides in proximal 0.4 length convex, in distal part almost straight, converging posteriorly; posterior end truncated, width 0.26 operculum width, posterolateral corners rounded, each with one SS.
Fig. 7

Dendromunna okhotensis sp. nov. ad Female, paratype (ZMH K-46577); gf male, paratype (MIMB 33583): a operculum; bd pleopods 3–5; e pleopods 1, 2, ventral view; f pleopod 1, lateral view, g pleopod 2. Scale bar 0.2 mm

Pleopod III (Fig. 7b) protopod length equal to width. Endopod length 1.5 width, distally with three pappose setae, lengths of setae 1.0–1.3 endopod length. Exopod basal article length 1.8 width and 0.70 endopod length, distal article length 2.9 width and 1.2 basal article length, tapering distally, with one terminal SS.

Pleopod IV (Fig. 7c) protopod length 0.76 width. Endopod length 1.5 width. Exopod length 2.5 width and about 0.9 endopod length, tapering distally.

Pleopod V (Fig. 7d) length 2.2 width.

Paratype, male: body (Fig. 8a, b) more slender, than in female, length 4.1 pereonite 4 width, body height 0.15 length; pereonite 1 length 0.03 body length; pereonites 2–7 length in relation to pereonite 1 length: 4.0; 5.8; 5.6; 3.7; 1.3; 0.77; pereonites 1–7 length–width ratios: 0.18; 0.56; 0.66; 0.63; 0.40; 0.18; 0.24. Pereonite five lateral expansions with bifurcated spine; pereonite six lateral expansions with simple spine. Pleotelson lateral margins each with six stout UBS.
Fig. 8

Dendromunna okhotensis sp. nov. Male, paratype (MIMB 33583): a Lateral view; b dorsal view; c pleotelson, ventral view; d antennae I, antenna II articles 1–4. Scale bar (ac 1 mm; d 0.2 mm

Antenna I (Fig. 8a, d) about 0.7 body length; articles 1–3 length–width ratios: 2.3; 2.5; 13.6; articles 2–3 lengths in relation to article 1 length: 0.75; 2.86; articles 1 and 2 with one and two distal BS respectively. Flagellum with 27 articles, article 1 length equal to width, article 2 length 7.3 width, article 18 with one fine SS distally, article 27 with five terminal SS.

Antenna II (Fig. 8d) articles 1–3 length–width ratios: 1.7; 0.54; 1.11; articles 2–3 lengths in relation to article 1 length: 0.42; 0.88; article 2 with long UBS distally, article 3 with long UBS and three traces of joining large setae distally; distal part of antenna II lost.

Pleopod I (Fig. 7e, f) length 3.0 width, lateral sides concave; distolateral lobes with 5–8 SS laterally; distomedial lobes extending 0.08 pleopod I length beyond lateral lobes, each lobe distolaterally with 7–8 SS.

Pleopod II (Fig. 7g, e) protopod length 4.8 width. Endopod basal article length 2.6 width, 0.34 protopod length; stylet length 0.71 protopod length. Exopod proximal lobe length 2.8 width, 0.22 protopod length; distal lobe overlapping distal part of protopod, bearing numerous fine long SS.

Uropods broken off in this specimen.

Remarks. D. okhotensis sp. nov. is rather similar to D. kurilensis sp. nov. Both species have a relatively slender body (length 3.7–4.0 width) and extremely long appendages (antenna I is about 0.7–0.8 body length, article 4 of antenna II is about 0.6–0.7 body length, bases of pereopods are about 0.2–0.3 body length). D. okhotensis sp. nov. can be distinguished from D. kurilensis sp. nov. by a more slender body (in D. kurilensis sp. nov. body length is 3.7 width in male, while in D. okhotensis sp. nov. it is 4.1 width in male and 3.8 width in female). The species differs also by the shape of the posterior part of pleotelson, whose high in D. kurilensis sp. nov. sharply decreases and extends posterior to the place of the uropodal insertion, while in D. okhotensis sp. nov. it gradually decreases and less extended. D. okhotensis sp. nov. bears stout setae on the pereonites 1–4 ventral surface in contrast to D. kurilensis sp. nov., a different number of maxilliped retinaculae (two vs one), and different members of the mandibular spine row (4–6 vs 3–4).

The body lengths of all other species of the genus do not exceed 3.1 width. In D. spinipes Menzies, 1962 antennae and pereopods were neither described nor illustrated. In the remaining three species these appendages are much shorter, than in the new species, e.g., antenna I ≤ 0.4 body length, article 4 of antenna II ≤ 0.3 body length.

D. kurilensis sp. nov. and D. okhotensis sp. nov. resemble D. compsa and D. mirabile, in having a short pereonite 1 (< 0.03 body length in all these species). Other two species of the genus, D. spinipes and D. bruuni, possess a long pereonite 1 (>0.07 body length). D. kurilensis sp. nov. and D. okhotensis sp. nov. differ from D. compsa and D. mirabile by the absence of a mandibular palp. The only other known species without a mandibular palp is D. spinipes.

In addition, the male pleopod I in D. okhotensis sp. nov. and D. kurilensis sp. nov. has concave lateral sides, while in D. compsa and D. bruuni the lateral margins of pleopod I are convex. D. spinipes and D. mirabile are known only by the female holotypes.

In both new species, males differ from females by a large number of articles in the antenna I flagellum.

Type locality. The Sea of Okhotsk from 46°56.556 N 151°05.013E–46°56.791 N 151°04.860E to 46°57.466 N 151°05.068E–46°57.494 N 151°04.917E, at depth 3299–3300 m.

Distribution. Known only from the type locality.

Key to the species of Dendromunna Menzies, 1962.

1. Pereonite 7 fused with pleotelson ……..........………… ...........................D. compsa Lincoln and Boxshall, 1983.

Pereonite 7 free, clearly distinguishable from pleotelson.. 2.

2. Pereonite 1 longer than 0.7 pereonite 2 length……… 3.

Pereonite 1 shorter than 0.1 pereonite 2 length....……… 4.

3. Mandible with palp…….…… D. bruuni George, 2004.

Mandible without palp……… D. spinipes Menzies, 1962.

4. Mandible with palp………..... D. mirabile Wolff, 1962.

Mandible without palp ……….......................………… 5.

5. Pereonites 1–4 ventrally with transverse elevations bearing strong setae; maxilliped endite with two retinaculae...................................... D. okhotensis sp. nov.

Pereonites 1–4 ventrally without setae; maxilliped endite with one retinacula ........…………D. kurilensis sp. nov.

Notes

Acknowledgements

The material from the Northwest Pacific Basin was collected and sorted during the KuramBio expedition with the RV Sonne with the financial support of the PTJ (German Ministry for Science and Education), grant 03G0223A to Prof. Dr. Angelika Brandt, University of Hamburg. The material from the Sea of Okhotsk was collected during the SokhoBio expedition with the RV Akademik M.A. Lavrentyev with the financial support of the Russian Science Foundation (Project No. 14-50-00034), and sorted with the financial support of the PTJ (German Ministry for Science and Education), grant 03G0857A to Prof. Dr. Angelika Brandt, University of Hamburg. The taxonomic processing of the material was supported by the Russian Foundation of Basic Research (project 16-04-01431). We thank the crews of the RV Sonne and Akademik M.A. Lavrentyev for their help on board and all student helpers and technicians for support and help with sorting of the extensive expedition material. This is KuramBio publication # 38.

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Copyright information

© Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.A.V. Zhirmunsky Institute of Marine Biology, National Scientific Center of Marine Biology, Far Eastern BranchRussian Academy of SciencesVladivostokRussia
  2. 2.Far Eastern Federal UniversityVladivostokRussia
  3. 3.Zoological Museum, Center of Natural HistoryUniversity of HamburgHamburgGermany
  4. 4.Senckenberg Gesellschaft für NaturforschungFrankfurtGermany

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