THE ORIGIN AND PRIMITIVITY OF SUBMARINE CAVE ORGANISMS

1.利用水肺分离器对日本内成岛和大东岛的海底洞穴生物进行了调查。根据这些岛屿的海底洞穴样品以及在小笠泽、帕劳和菲律宾群岛的海底洞穴样品，讨论了海底洞穴生物的多样性和起源，特别是软体动物。西北太平洋海底洞穴双壳类除了具有独特的组成特征外，还具有以下共同的重要特征：（i）成体贝壳尺寸较小（小于5 mm）;（ii）透明或半透明无色贝壳;（iii）表生和半底生种类多;（iv）深水属多;（v）频繁的子代变态;（vi）低繁殖力和育雏优势.海底洞穴腹足类动物还包括许多在深水中最为人所知的属。从早期发育来看，海底洞穴古腹足类表现为直接发育或短期游动的幼虫，而中腹足类和新腹足类则为浮游营养性和浮游性幼虫，与双壳类的情况不同。4.虽然海底洞穴双壳类物种似乎主要局限于浅水、神秘的环境，但海底洞穴腹足类通常来自邻近的深水底部，这表明这两个群体之间的起源不同。海底洞穴中的双壳类和腹足类显示了古生代和中生代浅水底部的贝壳结构和生活方式，在生态学上而不是分类学上指示原始静脉。在海底洞穴中不频繁的捕食似乎是建立这种独特生物群的因素之一，这种条件类似于“中生代海洋革命”之前的浅水海底。

1. Submarine cave organisms from Naisei and Daito Islands were investigated with the help of some SCUBA diviers. Base on the samples from the submarine caves of these islands as well as those collected from the Oagasasawa, Palau and Philippines Islands, I discussed the primitiveness and origin of the submarine cave organismas with special reference to the molluscs.2. In addition to the unique specific composition, common significant characteristics of the submarine cave bivalves in northwest Pacific are (i) reduced adult shell size (less than 5 mm), (ii) transparent or semi-transparent coloreless shells、(iii) many epifaunal and semi-infaunal species, (iv) many deepwater genera, (v) frequent paedomorphosis by progenetis, and (vi) low fecundity and dominance of brooding.3. Submarine cave gastropods also includes many genera most known from deepwaters. In view of early developnent, submarine cave archaeogastropods shows direct development or short-term swimming larvae, but the meso-and neogastropods are planktotrophic and pelagic larvae, the situation different from the bivalves.4. While the submarine-cave bivalve species seem to be limited mostly to shallow-water, cryptic environments, the submarine-cave gastropods are commonly known from the neighboring deepwater bottoms, suggesting different origins between the two groups.5. The bivalves and gastropods in the submarine caves show shell architectures and life styles that were dominated in Paleozoic and Mesozoic shallow-water bottoms, indicating primitivenes ecologically rather than taxonomically. Infrequent predation in the submarine caves seems to be one of the factors for estaglishing this unique biota, the condition similar to shallow-water marine bottoms before 'Mesozoic Marine Revolution'.