title: Morphology, Biology, and Phylogenetic Position of the Bivalve Platomysia rugata (Heterodonta: Galeommatoidea), a Commensal with the Sipunculan Worm Sipunculus nudus.
abstract: The bivalve superfamily Galeommatoidea is characterized by its symbiotic associations with other marine invertebrates. However, for many galeommatoideans, the host species remains unknown. Platomysia (Galeommatoidea) is a monotypic genus including a single species P. rugata, which is distinguished from other galeommatoideans in having distinct and evenly spaced commarginal ribs on its shell surface. This species was described based on a single right valve shell collected in Nanao Bay, Japan Sea, by Habe in 1951 and has been known only from Japanese waters. However, the biology of living animals has never been reported. We found that this species lives in the burrows of the sipunculan worm Sipunculus nudus in mud flats in the Seto Inland Sea, Japan. We investigated its host association and described its shell morphology and anatomy. In addition, we performed a phylogenetic analysis using two nuclear (18S and 28S ribosomal RNA) genes to determine its phylogenetic position in Galeommatoidea. The result suggests that this species belongs to the clade of commensal bivalves together with Pseudopythina, Byssobornia, and Pergrinamor. Platomysia rugata and other two groups of sipunculan-associated galeommatoideans were not monophyletic, suggesting that association with sipunculans occurred at least three times in the galeommatoid evolution.
authors: 1 Museum of Zoology and Department of Ecology and Evolutionary Biology, University of Michigan,1109 Geddes Avenue, Ann Arbor, MI 48109-1079, USA.|2 Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha,Kashiwa, Chiba 277-8564, Japan.|3 Graduate School of Human and Environmental Studies, Kyoto University,Yoshida-Nihonmatsu-cho, Sakyo, Kyoto 606-8501, Japan.
authors: Ryutaro
authors: R
authors: Goto
authors: 4 965-1 Kawachi-ko, Uwajima, Ehime 798-0075, Japan.
authors: Hiroshi
authors: H
authors: Ishikawa
authors: 5 14-16 Yakeyama-Hibarigaoka-cho, Kure, Hiroshima 737-0901, Japan.
authors: Yoichi
authors: Y
authors: Hamamura
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000235:genetics* / Q000502:physiology*; D010802:Phylogeny; D011077:Polychaeta / Q000502:physiology*; D013559:Symbiosis / Q000502:physiology*
keywords: Annelida; Galeommatoidea; Platomysia; Seto Inland Sea; Sipuncula; Sipunculus; burrow; commensalism; mud flat; symbiosis