The paleontological study on the origin and evolutin of submarine cave ostracodes from coral reefs.

为揭示琉球群岛海底洞穴介形类的区系特征和穴居塞班鱼新属的演化过程，本文列举了日本伊势岛“大同津”海底洞穴介形类组合的特征。(1)活着的个体非常罕见。活介形虫的罕见可能反映了海底洞穴的贫营养状况。(2)从“Daidokutsu”介形虫组合主要由浅水元素从洞外。特别是发现了三种塞班鱼，包括新属（1sp.），都被认为是源自深海祖先。(3)与其他介形类类群相比，“Daidokutsu”样品中的Cytheraceans在物种多样性和个体丰度方面相对较低。中侏罗世以来，在开阔海底环境中的介形类组合中，以介形类为主，而仅在琉球群岛海底洞穴中发现的一个新的穴居塞班鱼属可能起源于塞班鱼Cardobairdia或其近亲。这一新属很可能已经成功地在洞穴中的坚硬基质中定居，特别是利用洞穴墙壁和天花板上的裂缝作为其微栖息地。新属可能已经适应了这个神秘的栖息地，以应对强大的cytheracean竞争者，以及在黑暗和贫营养的海底洞穴中无法生存的捕食者，如腹足动物。新属与近缘属Saipanetta和Cardobairdia的区别在于刚毛较少，没有任何精细结构。爬行时，这种新属的甲壳张开得很大。能将甲壳打开的能力是足足肢类动物的原始行为特征之一。

The puropose of this study is to reveal the faunal characteristics of the submarine cave ostracodes from the Ryukyu Islands, and the evolutionary process of the new troglobitic saipanettid genus.The characteristics of the cave assemblages from "Daidokutsu" of Ie Island are enumerated as follows. (1) Living individuals are very rare. The rare occurrence of living ostracodes probably reflects the oligotrophic conditions of submarine caves. (2) The ostracode assemblages from "Daidokutsu" consist mostly of shallow water elements from outside the cave. Exceptionally, three saipanettid species, including 'new genus' (1sp.), are all thought to have derived from deep-sea ancestors. (3) Cytheraceans from the "Daidokutsu" samples are relatively low in species diversity and individual abundance compared to other ostracode taxa. The ostracode assemblages from various habitats of open sea floor environments have been dominated by cytheraceans since the middle Jurassic.A new troglobitic saipanettid genus, only found from submarine caves of the Ryukyu Islands, possibly derived from the saipanettid Cardobairdia, a deep-sea muddy bottom inhabitant, or its relatives. It is likely that the new genus has successfully colonized hard substrata in caves, particularly exploiting the crevices on cave walls and ceilings as its microhabitat. The new genus may have adapted to this cryptic habitat in response to strong cytheracean competetors, and to predators such as gastropods that do not survice well in dark and oligotrophic submarine caves. Insofar as well preserved appendages have been investigated, the new genus differs from the closely related genera Saipanetta and Cardobairdia in having fewer setae without any fine structure. While crawling, the new genus keeps its carapace widely gaped. The ability to open the carapace widely is one of the primitive behavioral features of podocopids.