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标题：Ovulation in Diplosoma (Tunicata, Ascidiacea, Didemnidae): a light microscopical study
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作者：Wolfgang Groepler
期刊名称：Helgoland Marine Research
印刷版ISSN：1438-3888
出版年度：2002
卷号：56
期号：2
页码：102-111
DOI：10.1007/s10152-002-0109-z
出版社：BioMed Central
摘要：Serial sections of non-ovulated and ovulated eggs of Diplosoma migrans (Tunicata, Ascidiacea, Didemnidae) were compared in order to study the process of ovulation on the level of light microscopy. Fully grown eggs are surrounded by an outer follicular epithelium consisting of cubic cells, and an inner follicular epithelium consisting of flat cells. Egg release is initiated by a fusion of the epidermis with the outer follicular epithelium at the distal pole of the egg. A contraction of the outer follicular epithelium leads to an opening of both epidermis and outer follicular epithelium, and their removal from the egg. The envelope of ovulated eggs corresponds to the former inner follicular epithelium. Mainly due to a contraction of the epidermis, the outer follicular epithelium is shifted into the abdomen and separates from the epidermis. It transforms into a vestigial body (corpus luteum) and finally atrophies. The epidermis flattens and resumes its typical appearance. On the basis of these observations, the results of studies on the closely related Diplosoma listerianum are discussed and questioned.
关键词：Ascidians; Egg ;envelopes; Ovulation