Early stalked stages in ontogeny of the living isocrinid sea lily Metacrinus rotundus
Early stalked stages in ontogeny of the living isocrinid sea lily Metacrinus rotundus
复制标题
活体异百合 Metacrinus rotundus 个体发育的早期茎阶段
作者：
Amemiya;S.;Omori;A.;Tsurugaya;T.;Hibino;T.;Yamaguchi;M.;Kuraishi;R.;Kiyomoto;M.;and Minokawa;T.
研究了Isocrinid海百合Metacrinus rotundus的早期有茎阶段，直至早期五角海百合阶段。在实验室中，诱导幼虫在双壳贝类壳上定居并培养，发育为晚期囊蚴。从非常早期到中期囊蚴的三维（3D）图像重建表明，由五个三联体组成的15个放射状足从新月形的水腔同步形成。水腔的方向表明，解决后幼虫倾斜向后。在非常早期的cystideans，口，桡，基部和下基部，每个有五个板在冠，约五个柱在柄，和五个终端干板在附件盘，已经形成。在中囊动物中，肛板出现在冠部。田间培养的晚期囊蚴在定居后约5个月发育为五角虫。这些pentacrinoids共享许多冠结构与成年海百合。另一方面，柄的许多特征与成年等海百合不同，但与羽状星星五角海百合的柄有许多共同特征，包括盘状近端柱、高而细长的中柱、从合轴关节发育而来的合关节、仅在近端柱中有限形成的纤毛和附着盘。根据这些发现，现存海百合目之间的系统发育关系进行了讨论。
The early stalked stages of an isocrinid sea lily,Metacrinus rotundus, were examined up to the early pentacrinoid stage. Larvae induced to settle on bivalve shells and cultured in the laboratory developed into late cystideans. Three‐dimensional (3D) images reconstructed from very early to middle cystideans indicated that 15 radial podia composed of five triplets form synchronously from the crescent‐shaped hydrocoel. The orientation of the hydrocoel indicated that the settled postlarvae lean posteriorly. In very early cystideans, the orals, radials, basals and infrabasals, with five plates each in the crown, about five columnals in the stalk, and five terminal stem plates in the attachment disc, had already formed. In mid‐cystideans, an anal plate appeared in the crown. Late cystideans cultured in the field developed into pentacrinoids about 5 months after settlement. These pentacrinoids shared many crown structures with adult sea lilies. On the other hand, many features of the stalk differed from those in adult isocrinids, while sharing many characteristics with the stalk of feather star pentacrinoids, including disc‐like proximal columnals, high and slender median columnals, synarthrial articulations developmentally derived from the symplexial articulations, limited formation of cirri only in the proximal columnal(s), and an attachment disc. On the basis of these findings, phylogenetic relationships among extant crinoid orders are discussed.