A study on the biodiversity of opisthobranchiate mollusks : diet specialization and speciation

该研究项目为大型藻类的食草专家--囊舌目的生物多样性研究做出了重要贡献。相模湾和冲绳都以后鳃类的高物种多样性而闻名，是本项目的主要研究区域。的多样性的食性，以及物种多样性的后鳃目是特别高的冲绳sacoglossan的主要食物，大型绿藻的多样性，也很高。该项目的主要成果是：1）。2）日本常见囊舌虫普拉西亚属（Placida sp.）2个隐种;（sensu Baba，1986）;发现这两个隐种的食性宽度比普拉西亚属的窄。（sensu Baba，1986）; 3）在Ercolania属中发现了另一个可能的隐种复合体; 4）一些以前根据齿舌形态被认为是不同种的囊舌纲动物被证明是种内变异;结果表明，某些囊舌藻种的齿舌形态变异较大：5）许多囊舌藻种的食物藻类在野外和实验室都得到了证实，有些囊舌藻种的食物藻类是首次记录; 6）对几种常见囊舌类物种的详细生态调查显示，有些物种的食性宽度比以前认为的要宽得多，（7）通过对日本囊舌藻的研究现状的回顾，指出囊舌藻的生物多样性研究还存在一些问题。最后，本项目的不同成果显示了未来几个重要的研究方向，不仅在囊舌鱼类，而且在其他后鳃类的生物多样性研究。

This research project has made marked contributions to the biodiversity study on the order Sacoglossa, whose members are mostly known as specialist herbivores of macroalgae. Sagami Bay and Okinawajima, both are well-known for a high species diversity of opisthobranchs, are the main study areas of this project. The diversification of feeding habit as well as the species diversity of this opisthobranchiate order was especially high in Okinawajima where the diversity of sacoglossan's primary food, macro-green algae, was also high. Major accomplishments of this project are 1) ca. 20 unrecorded species in Japan were found, many of which are likely to be undescribed ; 2) two cryptic species of a common Japanese sacoglossan, Placida sp. (sensu Baba, 1986), were found ; these two cryptic species were found to have narrower diet width than Placida sp. (sensu Baba, 1986) ; 3) another possible cryptic species complex was found in the genus Ercolania ; 4) some sacoglossans previously recognized as distinct species based on radular morphology were shown to be intraspecific variation; it was shown radular morphology might be highly variable in some sacoglossan species ; 5) food algae for many sacoglossan species were demonstrated both field associations and laboratory experiments; for some sacoglossans food algae were recorded for the first time ; 6) detailed ecological surveys on several common sacoglossan species revealed that some species have much wider diet width than previously thought, while more specialized food preference was suggested in some sacoglossan species ; 7) with a review of past researches on Japanese sacoglossans it was shown that there are a few challenges for the biodiversity study of Sacoglossa. Finally, diverse achievements of this project have shown several important future research directions in the biodiversity study not only on sacoglossans but also on other opisthobranchs.