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The reproductive system of planarians is considerably regular among different families, although the structures associated can be more or less complex. All planarians are hermaphrodites, so their reproductive system has a male and a female part. Both parts communicate with the surface of the body via a single opening called gonopore, which is located on the ventral side of the posterior half of the body. == Male part of the reproductive system == The male part of the reproductive system in planarians has a set of several testicles, distributed throughout the body in two or more rows. They are usually concentrated in the anterior two thirds of the body, although they can reach close to the posterior end. The testicles are connected to a pair of sperm ducts which run posteriorly towards the gonopore. In some groups, the sperm ducts met in their distal part, forming the ejaculatory duct, which then opens in a cavity called “male atrium”. In others, like land planarians, both open in the prostatic vesicle, a glandular organ which then runs posteriorly and becomes the ejaculatory duct. The male atrium is located anteriorly to the gonopore. Usually associated to the ejaculatory duct, there is a structure formed basically by a fold of the walls of the male atrium called “penis papilla”. The penis papilla may be a permanent structure, which occupies part or the whole male atrium, or a temporary one. A temporary penis papilla is formed only during copulation by a projection of the walls in the male atrium.〔Ogren, R. E. and Kawakatsu, M. (1990). ''Index to the specis of the family Geoplanidae (Turbellaria, Tricladida, Terricola) Part I: Geoplaninae.'' Bulletin of Fujis Women's College. 29: 79-166.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「reproductive system of planarians」の詳細全文を読む スポンサード リンク
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