Morphologic and crystallographic study on the skeletal homology of crinoids (Echinodermata)

在这一年里，我进行了两项与这笔拨款有关的主要研究：1)三种现代软骨类在发育阶段骨骼生长的扫描电子显微镜观察，2)关节亚纲可能跨越古生代-中生界的快速进化的化石证据。在相模湾的Koajiro Cove采集了日本水牛的物种，并监测了它们受精后的产卵和发育。此外，还观察到了另外两种节肢动物Antedon bifida和Decametra tigrina的五管虫期。主要研究结果如下：1.首次在五倍体中检测到肛板。这是寡头亚目首次报道肛板。肛板在古生代的三个亚纲中被广泛观察到，但从一些关节动物中发现的这一发现表明，它的存在不是关节的良好特征。这三个联轴节在五颈骨柄中都有共同的突触连接。目前的数据结合以前关于不同关节的五叉神经素的数据，表明五颈节茎中存在突触，这是节肢动物良好的突触特征。柱状物的数量可能在囊状期增加，但几乎是恒定的，并且在五孔状物阶段观察到各柱状物的纵向生长。此外，关于晚二叠世-早三叠世关节的数据，两个标本(日本东北部，内华达州)和参考文献的数据显示：4.越过边界，手臂上的韧带关节的数量突然减少，关节在韧带活动时获得了手臂自断的能力。这种进化的新颖性必须与关节的成功密切相关。

In this year I conducted two major researches in relation to this grant ; 1) SEM observation of the skeletal growth during developmental stages of three species of modern comatulids, 2) Fossil evidence about the presumable rapid evolutionary changes of the subclass Articulata across the Paleozoic-Mesozoic boundary.Specimens of Oxycomanthus japonicus were collected from Koajiro Cove of Sagami Bay, and their spawning and development after fertilization were monitored. Also, pentacrinoid stage of two other comatulids, Antedon bifida and Decametra tigrina, were observed. The results include :1. Anal plate was detected in pentacrioids of Oxycomanthus j. for the first time. This is the first report of anal plate from the suborder Oligophreatina. The anal plate were widely observed in the three subclasses of the Paleozoic, but this discovery from some articulata implies that its existence cannot be a good character of the articulata.2. All three comatulids share synarthrial articulation in the pentacrinoid stalk. The present data, combined with previous data about pentacrinoids of various articulates, suggest that existence of synarthry in the pentacrinoid stalk would be a good synapomorphic character of the Articulata.3. The number of columnals probably increases during the cystoid stage, but it is almost constant and longitudinal grow of each columnals are observed during the pentacrinoid stage.Also data about Late Permian-Early Triassic articulates, both specimens (NE Japan, Nevada) and data from reference papers, shows the following :4. Across the boundary, the number of ligamentary articulations in the arms suddenly decreased, and articulates have acquired the ability of arm autotomy at ligamentary acticulations. This evolutionary novelty must deeply be related to the suceess of the Articulata.