Host Species for Glochidia of the Freshwater Unionid Mussel Lanceolaria grayana in Tanks

摘要

The freshwater unionid mussel Lanceolaria grayana inhabits ponds and rivers in East Asia (Japan, Korea, China and Russia: Kondo, 2008; Miura & Fujioka, 2015). Larvae of unionid mussels (glochidia) are known to parasitize live fish (Itoh et al., 2008;Kondo, 2008; Itoh et al" 2014, 2016). At the end of their parasitic stage, they metamorphose into juveniles and detach from their host to settle on the riverbed (Fukuhara et al" 1990; Kondo, 2008; Negishi et al" 2008). The typical shape (subtriangular with a pair of hooks入the size (about 0.24 mm in shell length; about 0.22 mm in shell depth) and some of the host species of the glochidia of L. grayana have previously been examined (Higashi & Hayashi, 1964; Kondo, 1997, 2008). Glochidia of L, grayana have been found to parasitize three fish species, the Pale Chub (Opsariichthys platypus), Dark Chub (Candidia temminckii) and Amur Goby {Rhinogobius sp.) by confirming that they stay on the host fish for seven days (Kondo, 1989). Glochidia ofしgrayana and L. oxyrhyncha (a synonym or subspecies of L. grayana from Lake Biwa) parasitize several other fish, such as the Ayu Sweetfish {Plecoglossus altivelis), oin-buna (Carassius sp.), another Dark Chub (Ca. siebokUi), the Topmouth Gudgeon (Pseudorasbora parva)and the Japanese Loach (Misgurnus anguillicaudatus). Some of these fish are known to be unionid hosts (Kondo, 1997, 2008; Kondo et al" 2011) but glochidia have sometimes been recorded from others that are still not confirmed as hosts. In any case where the glochidia were able to complete the development stages through to metamorphosis into juveniles, the fish were recognized as suitable host species (Itoh et al., 2008; Itoh et al" 2014, 2016). In this study, we report on suitable host species forglochidia and juveniles of L. grayana collected in Okayama Prefecture, Japan.