Natural history of submarine cave organisms in Indo-Pacific

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Kase & Kinjo (1996) found a cave nassaried gastropods and Kase (1998) described 16 new species of the Pickworthiidae typical of caves. Kase and Kano (in press) described an enigmatic new genus and species from a submarine cave of Palau, possibly with neritopsine affinity .Hayami (1998) presents a hypothesis from analyses of size changes of bivalves in time and space and reproductive adaptation of cave bivalves that oligotrophic condition are responsible for the mass extinctions caused by various geologic and astronomical events. Although various environmental factors may influence the body size of organisms, recent knowledge of deep-sea and submarine cave faunas indicates that food supply is of prime importance as a factor controlling the adult size and adaptive strategy of bivalves.Significant shell-size reductin of bivalves seems to have occurred at the same time with Permian/Triassic and Cretaceous/Tertiary mass extinctions, probably because large-sized species (or group) were selec … More tively eliminated.Takeda (1998) described 6 species of crabs collected in submarine caves around Koror Island, Palau : Schizophyrys dahlak (Majidae), Carupa ohashii, Chair ybdis paucidentata and Laleonectes nipponensis (Pornidae), and Lentilumnus tatimanus and Pilumnus sp. (Pilumnidae). S.dahliak had been known only from the Red Sea and Ch. paucidentata from the western Indian Oceans. Species of the Majidae and Purtunidae seems to be cave inhabitants.A living fossil sigillid genus, Kasella, was first discovered from submarine caves (Tabuki & Hanai, in press). Sigillids are primitive podocopid ostracods having ancient characters Kasella is possibly derived from the sigillid Cardobairdia of deep-waters. It is likely that Kasella has successfully colonized hard substrates in caves, particularly exploiting the crevices on cave walls and ceilings as its microhabitat. Kasella may have adapted to this cryptic habitat in response to strong cytheracean competitors and predators such as gastropods that do not survive well in dark and oligotrophic submarine caves. Less