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

本研究以姬蜂目为研究对象。是日本原始介形类的一个分类群，关于介形类的生态和栖息地的研究尚未见报道。在经验中，最多的个体是从附着在双胞爱胜球根状突起周围的沉积物中采集的。为了更详细地了解它们的栖息地和行为，观察了一些活体标本。结果，以下事实变得清晰起来：它们只使用触角、触角和羽毛移动；它们的栖息地不是在表面，而是在粗沙颗粒之间。由于它们的基本体型与龟甲总科的基本体型是相同的，因此其他扁形目昆虫的生活型应该基本相同。本文阐明了个体发育和比较解剖学的观点。这些知识将支持对原始介形动物进化的理解1)它们在个体发育中有9个幼虫。(2)雌雄交配器官在A-3期(6龄)均以原基出现，并在此阶段及以后观察到两性二型性。3)该分类单元的早期诊断特征，如节状主干、双分枝触角等。4)它们有一双无节幼虫的眼睛。5)肛门开口不在背侧，而在腹侧。6)在肛门段之后有一个单位，它是一个肛门。7)端子产生了一对类似肢体的器官‘Furcae’，它与Podocopina中的‘尾侧分支’不是同源的。8)羽毛继续发育，直到最后一次蜕皮。(9)雌雄交配器官均起源于第4主干。

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.