NATURAL HISTORY OF SUBMARINE CAVE ORGANISMS

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1.Two new genus and 4 new species of the family Pickworthiidae (characteristic in submarine caves) and a new genus and species of the family Scissurellidae were described from the Indo-Pacific submarine caves. One new genus and species whose shell morphology has not been known was also described.2.Analysis of shell characters of the gastropod genus Pisulina resulted to recognize six species, of which two are new, and clarified that they constitute a monophyletic group together with the genus Neritilia and other related new genera. An anatomical study of Pisulina and Neritilia supported the result of our conchological study.3.One fossil species previously identified questionably to a living neritid species is recognized as a new genus and species of the family Neritiliidae, indicating that the family adopted cryptic environments at least by an Oligocene time.4.Two new genera and several new species of the family Neritiliidae were found from anchialine and hyporheic habitatas and river streams. This is the first discovery from mollusks from such environments except for a hydrobiid gastropod.5.Anatomical and molecular phylogenic analyses of the superorder Neritopsisna including the family Neritiliidae show that the superorder invaded land at least three times in their history, and also show that neritiliids in river streams were derived from those once adapted to marine cryptic environments via the anchialine and hyporheic environments.6.One new species of calanoid copepod genus Ridgewayia was described from a submarine cave in Palau This new species is related to a Caribbean species, suggesting westward dispersal from the Caribbean Sea. This study also found 4 new species of the mysid genus Heteromysoides and Heteromysis. One living fossil new genus and species of ostracod, Kasella ryukyuensis, was described from the submarine caves on Okinawa.