Study on morphology, ecology, biogeography and systematics of primitive ostracod Platycopa

本文对日本原始介形虫类Platycopa的分类群Keijcyoidea sp.进行了研究。目前还没有关于白嘴龙的生态和生境的报道。在试验中，收集到的个体数量最多的是附着在自行车爱森草根茎周围的沉积物。为了更详细地了解它们的栖息地和习性，我们对一些活标本进行了观察。结果，下列事实变得清楚：他们只使用天线、天线和天线移动；它们的栖息地不在地表，而在粗糙的沙粒之间。认为其他鸭嘴兽种的基本身体形态与keijcyosp相似，因此它们的生活方式几乎相同。本文在个体发生和比较解剖学上阐明了以下几点。这些知识将支持对原始介形虫白嘴龙进化的认识。1)它们有9个个体发育阶段。2)两性的交配器官在A-3（6龄）以原色素的形式出现，并在此阶段及之后出现两性二态性。3)该分类群的早期诊断特征为有节的躯干、双支的触角。4)眼睛难看。5)肛门开口位于腹侧而非背侧。(6)肛门节后存在一个单位；这是一台电视机。7) telson衍生出一对肢状器官“furcae”，这与Podocopina中的“尾支”不同源。8)furcae继续发育直到最终蜕皮。9)两性的交配器官均来自树干第4节。

This research focused on Keijcyoidea sp. which is a taxon of primitive ostracod Platycopa from Japan.There is no report on the ecology and habitat of Platycopa at all. In the experience, the largest number of individuals were collected from the sediments which attached around the rhizoid of Eisenia bicyclis. In order to know the habitat and behavior in detail, some living specimens were observed. As a result, the following facts became clear : they use only antennule, antenna and furcae for moving ; their habitat in not surface but between coarse sand grains. It is suggested that other Platycopa species must have almost the same life style because the basic body plan of them is common to the Keijcyoidea spThe following points of ontogeny and comparative anatomy were made clear. These knowledge will support the understandings of evolution on the primitive ostracod Platycopa.1) They have 9 instars in ontogeny. 2) Copulatory organs of both sexes appear in A-3 (6th instar) as anlagen and the sexual dimorphism is observed in and after this stage. 3) Diagnostic characters of this taxon e.g. articulate trunk, bi-ramous antenna appear in the early stages. 4) They have nauplius eyes. 5) the anal opening are located at not dorsal side but ventral side. 6) An unit exists after the anal segment ; it is a telson. 7) The telson derives a pair of limb-like organ 'furcae' which is not homologous to 'caudal rami' in Podocopina. 8) furcae continue to develop until the final moult. 9) The copulatory organs of both sexes are derived from the 4th trunk segment.