Study on plesiomorph and phylogeny of "living fossil" Ostracoda (Crustacea)

“活化石”介形纲（甲壳纲）的拟形体及系统发育研究

基本信息

批准号：
14340267
负责人：
TSUKAGOSHI Akira
金额：
$ 9.41万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14340267/
关键词：
Ostracoda Crustacea living fossil evolution body segment Taxonomy diversity relict species 祖先形質原始性分類

项目摘要

A new species of genus Keijcyoidea with some plesiomorphic characters such as simple hingement, biramous antenna, clear body segments of urosom, was described as Keijcyodea infralittoralis Tsukagoshi, Okada and Horne, 2006. And its ecological nature (habitat and behavior) was also showed. Furthermore, all appendages and carapaces of all instars through the ontogeny were completely illustrated and described in the first time in Platycopida. The seventh limb which is lacking in adult was observed in younger juvenile. Therefore the lacking of the seventh limb is an autapomorphic character and the existence in younger instar suggests that Platycopida and Podocopida share a common ancestor. Though the appendage additional pattern is largely different from the Podocopida, it is suggested that the difference comes from the habitat and behavior in coarse sand sediments rather than the phylogenetical reason.It is well known that common ostracods use the apical point of mandible for opening the both valves. But the platycopan ostracods including Keijcyodea infralittoralis do not so develop the point of mandible. After detail observations, the two new facts were regarded, i.e. : 1)the furcral point of inner carapace surface, which corresponds to the apical point, sifts to anterior side in platycopans ; 2)the anterior sifted furcral point corresponds to the humb-like process in the basal part of antenna in Platycopida. These facts mean that the platycopans do not use the mandible but the antenna for valve opening. The difference is also supported by the observation of muscle network system. The method for valve opening must come from the evolution of eating habit.

一种新的keijcyoidea属，具有某些倍形性特征，例如简单铰链，幼稚天线，尿素的透明身体片段，被描述为Keijcycyodea Infralittoralis tsukagoshi，Okada和Horne，2006年。还显示了其生态性质（栖息地和行为）。此外，在铂虫中首次完全说明和描述了通过本体发育的所有幼虫的所有附属物和甲壳。在年轻的少年中观察到成人缺乏的第七个肢体。因此，缺乏第七肢是一个自构特征，年轻龄的存在表明铂虫和podocopida具有共同的祖先。尽管附属的附加模式与podocopida有很大不同，但建议差异来自粗砂沉积物中的栖息地和行为，而不是系统发育理由。众所周知，常见的ostracods使用下颌骨的顶点来打开两个阀门。但是，包括keijcyodea infralittoralis在内的铂copan ostracods并没有发展下颌骨。经过详细的观察，考虑了两个新事实，即：1）内甲壳表面的粪便点，与顶点相对应，将其筛分到铂copan的前侧； 2）前筛分的刚毛点对应于铂虫天线基底部分的humb样过程。这些事实意味着铂型不使用下颌骨，而是用于阀门开口的天线。观察肌肉网络系统也支持差异。开口阀的方法必须来自饮食习惯的发展。