カワニナの生殖器官の解剖組織学的研究

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The reproductive system of the ovoviviparous freshwater prosobranch Semisulcospira libertina was studied anatomically and histologically. The male system consists of the testis, the vas deferens and the spermatophore organ, without the penis. The female system consists of the ovary, the oviduct, the spermatophore bursa, the seminal receptacle and the brood pouch. The spermatophore bursa receives only sperm mass from the spermatophore accepted. The seminal receptacle contains typical spermatozoa attached to its wall with their heads. Fertilization seems to take place in the proximal end of the brood pouch into which the sperm channel from the seminal receptacle opens. The brood pouch is divided into many brood chambers whose epithelium consists of a single layer of cuboidal cells without gland cells, and chambers are mutually connected by a small slit. The embryos at earlier developmental stages are contained in the proximal portion of the brood pouch, and the embryos at more advanced stages in more anterior distal portion. The birthpores located at the anterior portion of the brood pouch are several irregular slits formed in the epithelium at the underside of the brood chamber. The probable process of development and degeneration of brood chambers is discussed.
1989-12-31