A possible new ideal animal for the evolutionary biology-Aiming to demonstrate "pore-clock" in Ostracoda

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This project was focused whether or not Ostracoda, a group of small Crustaceans, could be an ideal material for evolutionary biology after studying the DDP analyses (Differentiation of Distribution of Pore-systems) extensively. We insisted that if the DDP analysis could be applicable to all the ostracode taxa and it could serve as a similar role of molecular clock for Ostracoda. Pore is a sensilla which come out through ostracode carapace and therefore could be preserved even in fossil carapaces as a small hole. The phylogenetic relationship between species of Cythere was already studied by the process to differentiate pore-pattern. The DNA analyses of Cythere revealed that the phylogeny estimated by the DDP analyses is quite consistent with the phylogeny based on DNA analyses. However, the rate of the change of base pair were found larger than those previously reported for other Crustaceans.The higher taxonomic plylogeny was also examined by the DDP analyses. The relationship within Loxoconchidae (family), Cytheroidea and Cyprioidea (superfamily), and Podocopida (order) were estimated by the DDP analyses, and results seems to be good ones. This is because the higher the taxonomic level goes, the earlier the differentiation of pore pattern will appear between the taxa. The tendency has been also found that in the taxa with more number of pores, such as Bairdoidea and Cyprioidea, the stage in which the pore pattern starts to differentiate comes to be earlier than the taxa with fewer pores, i.e. Cytheroidea. This indicate that an interesting evolutionary scenario, Cytheroidea has evolved and diversified paedomorphologically in post-Mesozoic era. DNA analyses for the relationship of higher taxa still undertaken. However Ostracoda has been proved to be one of the excellent animal for the evolutionary study because of pores, which can be a clock preserved in fossils.