Sperm Storage in the Reproductive Tract and Prolonged Survival of the Graafian Follicle in the Female Orange Whiskered Bat, <I>Myotis formosus tsuensis</I>, of Korea<SUP>*</SUP>

概要

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Ultrastructural observations revealed that the orange whiskered bat belongs to the'prolonged sperm storage'type, in which copulation takes place probably in late October and ovulation occurs after arousal from hibernation in spring. The principal site of sperm storage was the caudal isthmus of the oviduct, where spermatozoa had intimate relationships with indentations of the non-ciliated epithelial plasma membrane, but some dead spermatozoa were engulfed by the epithelial cells. Abundant glycogen found in the non-ciliated epithelial cells was regarded as a nutrient source for prolonged sperm storage. Considerable numbers of spermatozoa were observed also in the uterus and uterotubal junction. A single Graafian follicle found in either ovary had an oocyte with a germinal vesicle at the dictyotene stage in prophase of meiosis I (resting stage) throughout hibernation from early November to late March, while the oocyte in the bats administered with gonadotrophic hormones in late March was in anaphase of meiosis I. Heavy glycogen content in the cumulus cells may be of nutrient value for the prolonged survival of the ovum. The 'prolonged sperm storage'type was considered as a reproductive strategy for species preservation, by which their young are adjusted to be born in hot summer when insect food is abundant.
日本哺乳類学会の論文