水螅的反口孔结构和功能

STRUCTURE AND FUNCTION OF THE ABORAL PORE OF PELMATOHYDRA PSEUDOLIGACTIS

在２３０个水螅（Ｐｅｌｍａｔｏｈｙｄｒａｐｓｅｕｄｏｌｉｇａｃｔｉｓ）中观察到３８例反口孔排物过程。反口孔静止时，基盘附着层外表中心见不到孔迹。反口孔开启时，有废物或气体从孔内排出。连续切片检查，发现反口孔排物前，基盘腔内堆积有食泡残骸等许多废物，孔周死亡细胞和断裂废弃的中胶层在反口孔开启时脱落。非排物期，基盘附着层中心处缺少中胶层。根据观察结果，对反口孔的结构特点及其生理功能作了讨论。

Basal disk of Pelmatohydra pseudoligactis was observed under dark field microscope. 38 among 230 individuals were observed excreting excrement through aboral pores. Aboral pore was closed in motionless state. Opening of the aboral pore is accompanied by extension of the basal disk or swelling of the center of basal disk. Debris of food vacuole or gas was excreted through the aboral pore. This process repeated about 1-3 times and lasted less than 2 minutes. The aboral pore was closed after excretion. The aboral pore was also examined in histological sections. There was some excrement in it before excretion. the dead cells surrounding it fell off during the course of excretion. The center of basal disk lacks mesoglea in the motionless state. The physiological function of the aboral pore was discussed.