アコヤガイ幼生の消化器官系の発達

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Electron microscopic observation was carried out on digestive system of immature D-stage larvae, early D-stage larvae, early umbonal larvae, early pediveliger, early spat and seed in Pinctada fucata. On and after early D-stage, alimentary canal consisted of esophagus, anterior stomach, posterior stomach, style sac, intestine, and digestive gland. The length and diameter of esophagus grew with increase of shell length. At the early D-stage, microvilli of anterior stomach were as long as those of posterior stomach. On and after early umbonal stage, microvilli of anterior stomach did not exist, while those of posterior stomach were extending. Style sac bore dense cilia of uniform length on and after early umbonal stage. Crystalline style in style sac and stomach were formed in early pediveliger. Intestine came to curve at early umbonal stage, and then the curvature became complicated according to growth. Digestive gland at early D-stage consisted of the cells with a large amount of rough-surfaced endoplasmic reticula. The gland grew digestive diverticula which consisted of two kinds of cells until umbonal stage. Mid gut appeared at early pediveliger. Wandering cells adjacent to digestive system of planktonic larva extended considerably long psedopodia which are likely to be basal lamina. The metamorphosis results in that growing direction of the posterior body wall and digestive diverticula changes from dorsoventral axis to antero-posterior axis. The wrenchs of viscus took place in early umbonal stage and metamorphic period. These periods correspond with the critical periods when many larvae often die. The growth rate of shell length corresponded with an increase of feeding which is related closely with a development of digestive system.
日本貝類学会の論文
1995-09-30

アコヤガイ幼生の消化器官系の発達

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