Abstract
We report the typical shape and average size of the glochidia and juveniles of Cristaria tenuis in Ishigakijima Island, Okinawa Prefecture, Japan, together with some new host species. The shape of the living glochidia was subtriangular and hooked. The average length, height, and width were 221.5 μm, 228.0 μm, and 108.3 μm. The host species for glochidia of the freshwater unionid mussel Cr. tenuis collected from Ishigakijima Island, were identified by determining whether these glochidia infected the following fish taxa: Cyprinus carpio, Carassius auratus langsdorfii, Ca. auratus, Rhodeus ocellatus ocellatus, Misgurnus anguillicaudatus, Clarias fuscus, Oryzias latipes, Poecilia reticulata, Macropodus opercularis, Oreochromis sp., Eleotris melanosoma, Hypseleotris cyprinoides, Rhinogobius spp., Rhinogobius giurinus, and Monopterus albus. The fishes were kept in tanks for 9–17 days, and the numbers of glochidia and metamorphosed juveniles detached from the hosts were counted. The juveniles were found to detach from the bodies of Cl. fuscus, Ory. latipes, Po. reticulata, Ma. opercularis, E. melanosoma, H. cyprinoides, Rhi. sp., and Rhi. giurinus. The number of glochidia infecting the fishes, the infection site, and the rate of glochidial encystment were determined using formalin-fixed fishes of the taxa Ca. auratus langsdorfii, P. reticulata, Gambusia affinis, Ore. sp., E. melanosoma, and H. cyprinoides collected from Ishigakijima Island. Glochidia were found to infect two host species: Po. reticulata and Ore. sp. Most glochidia were attached to the gills and fins of the fishes. A higher number of glochidia were found to attach and encyst on Po. reticulata than on Ore. sp. Po. reticulata was identified as a suitable host species for the glochidia of Cr. tenuis, in addition to Rhi. sp. and Ma. opercularis.
