Sagamiscintilla thalassemicola (Bivalvia: Galeommatoidea: Galeommatidae sensu lato) is a white-robed commensal clam that lives on the body surface of spoon worms (Annelida: Echiura). This species was described based on specimens collected from the spoon worm Anelassorhynchus mucosus (Thalassematidae) in Amakusa, Kyushu, Japan, in 1962, but there has been no reliable record since the first description. Thus, some researchers suspected that this species may have become extinct. In this study, we rediscovered this species from the spoon-shaped proboscis of the echiuran Anelassorhynchus sp. in Shikoku and Kyushu Islands, Japan. Although the original description did not mention the details of its host use pattern, we found that this species lives almost exclusively within the proboscis gutter of the host, where it is almost hidden from the outside. Such a cryptic habitat is probably the reason why this species has remained undiscovered for over 50 years. Living hidden in the host probosces probably provides an anti-predation benefit for S. thalassemicola. The host echiurans create ciliary water currents on the proboscis gutter to transfer food particles into the mouth, and the bivalves can utilize this water currents for respiration and filter feeding. Sagamiscinitlla thalassemicola is distinctive among ectocommensal galeommatoideans in having a mantle that fully covers the shell valves. It may be a morphological adaptation to protect the shell valves from sand and other hard particles transferred through the proboscis gutter of the host.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Price excludes VAT (USA)
Tax calculation will be finalised during checkout.
Anker A, Murina GV, Lira C, Vera Caripe JA, Palmer AR, Jeng MS (2005) Macrofauna associated with echiuran burrows: a review with new observations of the innkeeper worm, Ochetostoma erythrogrammon Leuckart and Rüppel, in Venezuela. Zool Stud 44:157–190
Boss KJ (1965) Symbiotic erycinacean bivalves. Malacologia 3:183–195
Chuang SH (1962) Feeding mechanism of the echiuroid, Ochetostoma erythrogrammon Leuckart & Rueppell, 1828. Biol Bull 123:80–85
Coan EV, Valentich-Scott P (2012) Bivalve seashells of tropical west America: marine bivalves from Baja California to northern Peru. Santa Barbara Museum of Natural History Monographs 6: iii–xv + 1–1258, pls. 1–326
Goto R (2016a) A comprehensive molecular phylogeny of spoon worms (Echiura, Annelida): implications for morphological evolution, the origin of dwarf males, and habitat shifts. Mol Phylogenet Evol 99:247–260
Goto R (2016b) The Echiura of Japan: diversity, classification, phylogeny and their associated fauna. In: Motokawa M, Kajihara H (eds) Species Diversity of Animals in Japan. Springer, Tokyo, pp 513–542
Goto R, Kato M (2012) Geographic mosaic of mutually exclusive dominance of obligate commensals in the symbiotic communities associated with a burrowing echiuran worm. Mar Biol 159:319–330
Goto R, Hamamura Y, Kato M (2007) Obligate commensalism of Curvemysella paula (Bivalvia: Galeommatoidea) with hermit crabs. Mar Biol 151:1615–1622
Goto R, Hamamura Y, Kato M (2011) Morphological and ecological adaptation of Basterotia bivalves (Galeommatoidea: Sportellidae) to symbiotic association with burrowing echiuran worms. Zool Sci 28:225–234
Goto R, Kawakita A, Ishikawa H, Hamamura Y, Kato M (2012) Molecular phylogeny of the bivalve superfamily Galeommatoidea (Heterodonta, Veneroida) reveals dynamic evolution of symbiotic lifestyle and interphylum host switching. BMC Evol Biol 12:172
Goto R, Okamoto T, Ishikawa H, Hamamura Y, Kato M (2013) Molecular phylogeny of echiuran worms (Phylum: Annelida) reveals evolutionary pattern of feeding mode and sexual dimorphism. PLoS ONE 8:e56809
Goto R, Ishikawa H, Hamamura Y, Sato S, Kato M (2014) Evolution of symbiosis with Lingula (Brachiopoda) in the bivalve superfamily Galeommatoidea (Heterodonta), with description of a new species of Koreamya. J Mollus Stud 80:148–160
Goto R, Ishikawa H, Hamamura Y (2016a) The enigmatic bivalve genus Paramya (Myoidea: Myidae): symbiotic association of an East Asian species with spoon worms (Echiura) and its transfer to the family Basterotiidae (Galeommatoidea). J Mar Biol Ass UK 97:1447–1454
Goto R, Ishikawa H, Hamamura Y (2016b) Symbiotic association of the bivalve Tellimya fujitaniana (Galeommatoidea) with the heart urchin Echinocardium cordatum (Spatangoida) in the northwestern Pacific. Zool Sci 33:434–440
Habe T (1962) Achasmea thalassemicola sp. nov., a new commensal bivalve found in an echiuroid, Thalassema mucosum Ikeda. Venus 22:117–119
Habe T (1981) A catalogue of molluscs of Wakayama Prefecture, the province of Kii 1. Bivalvia, Scaphopoda and Cephalopoda. Seto Mar Biol Lab Spec Publ Ser 7:1–303
Huber M (2015) Compendium of Bivalves 2. A full-color guide to the remaining seven families. A systematic listing of 8500 bivalve species and 10500 synonyms. ConchBooks, Harxheim
Ikeda I (1904) The Gephyrea of Japan. J Coll Sci Imp Univ Tokyo 20:1–87
Itani G, Kato M, Shirayama Y (2002) Behaviour of the shrimp ectosymbionts, Peregrinamor ohshimai (Mollusca: Bivalvia) and Phyllodurus sp. (Crustacea: isopoda) through host ecdyses. J Mar Biol Ass UK 82:69–78
Kato M (1998) Morphological and ecological adaptations in montacutid bivalves endo- and ecto-symbiotic with holothurians. Can J Zool 76:1403–1410
Kato M, Itani G (1995) Commensalism of a bivalve, Peregrinamor ohshimai, with a thalassinidean burrowing shrimp, Upogebia major. J Mar Biol Ass UK 75:941–947
Li J, Ó Foighil D, Middelfart P (2012) The evolutionary ecology of biotic association in a megadiverse bivalve superfamily: sponsorship required for permanent residency in sediment. PLoS ONE 8:e42121
Li J, Ó Foighil D, Strong EE (2016) Commensal associations and benthic habitats shape macroevolution of the bivalve clade Galeommatoidea. Pro R Soc B 20161006:283
Lützen J, Nielsen C (2005) Galeommatid bivalves from Phuket, Thailand. Zool J Linnean Soc 144:261–308
Mikkelsen PM, Bieler R (1989) Biology and comparative anatomy of Divariscintilla yoyo and D. troglodytes, two new species of Galeommatidae (Bivalvia) from stomatopod burrows in eastern Florida. Malacologia 31:175–195
Mikkelsen PM, Bieler R (1992) Biology and comparative anatomy of three new species of commensal Galeommatidae, with a possible case of mating behavior in bivalves. Malacologia 34:1–24
Morton B (1972) Some aspects of the functional morphology and biology of Pseudopythina subsinuata (Bivalvia: Leptonacea) commensal on stomatopod crustaceans. J Zool (Lond) 166:79–96
Morton B (1973) The biology and functional morphology of Galeomma (Paralepida) takii (Bivalvia: Leptonacea). J Zool (Lond) 169:133–150
Morton B (1981) The biology and functional morphology Chlamydoconcha orcutii with a discussion on the taxonomic status of the Chlamydoconchacea (Mollusca: Bivalvia). J Zool (Lond) 195:81–121
Morton B, Scott PH (1989) Hong Kong Galeommatacea (Mollusca: Bivalvia) and their hosts, with descriptions of new species. Asian Mar Biol 6:129–160
Paulay G (2003) Marine Bivalvia (Mollusca) of Guam. Micronesica 35–36:218–243
Sato S, Owada M, Haga T, Hong J-S, Lützen J, Yamashita H (2011) Genus-specific commensalism of the galeommatoid bivalve Koreamya arcuata (A. Adams, 1856) associated with lingulid brachiopods. Mollus Res 31:95–105
Wada K, Nishihira M, Furota T, Nojima S, Yamanishi R, Nishikawa T, Goshima S, Suzuki T, Kato M, Shimamura K, Fukuda H (1996) Present status of estuarine locales and benthic invertebrates occurring in estuarine environment in Japan. WWF Jpn Sci Rep 3:1–182
We are grateful to Takuma Haga (National Museum of Natural and Science, Tokyo, Japan) for providing us the echiuran specimen collected in Minami Satsuma.
This study was partially supported by grants to RG from the Japan Society for the Promotion of Science (JSPS) Research Fellowship for Young Scientists (no. 12J07151), JSPS Postdoctoral Fellowship for Research Abroad (no. 27-186), and JSPS KAKENHI (no. 17H06795).
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed by the authors.
Sampling and field studies
All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable.
Communicated by G. Steiner
Rights and permissions
About this article
Cite this article
Goto, R., Ishikawa, H. An unusual habitat for bivalves: rediscovery of the enigmatic commensal clam Sagamiscintilla thalassemicola (Habe, 1962) (Bivalvia: Galeommatoidea) from spoon worm’s spoon. Mar Biodiv 49, 1553–1558 (2019). https://doi.org/10.1007/s12526-018-0897-2