The fate of received sperm in the reproductive tract of a hermaphroditic snail and its implications for fertilisation |
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Authors: | Joris M Koene Kora Montagne-Wajer Dick Roelofs Andries Ter Maat |
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Institution: | (1) Department of Animal Ecology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands;(2) Max-Planck-Institut für Ornithologie, Postfach 1564, 82305 Starnberg, Germany |
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Abstract: | Multiple mating, sperm storage and internal fertilisation enhance sperm competition. The great pond snail can use stored sperm
for over three months, and frequently mates with different partners. This hermaphrodite, Lymnaea stagnalis, can also self-fertilise and often produces egg masses containing both selfed and outcrossed eggs. Hence, a sperm recipient
may exert considerable control over paternity. Using microsatellite markers, we show that when allosperm are present, all
genotyped eggs are cross-fertilised. We also find that sperm have the opportunity to compete, because double matings lead
on average to equal paternity for each sperm donor. This indicates that received sperm are randomly mixed in storage. To gain
further insight into the mechanisms underlying the process of sperm storage, digestion and utilisation, we investigated the
fate of donated sperm at different times after copulation. We find that within 3 h after transfer most sperm have been transported
into the sperm-digesting organ. Fluorescent labelling of sperm in histological sections further reveals that allosperm are
not stored in the fertilisation pouch, but upstream in either the hermaphroditic duct, seminal vesicles, or ovotestis. Besides
contributing to the understanding of the mechanisms underlying sperm competition and/or cryptic sperm choice, this study shows
that mixed mating cannot be treated as a separate issue in hermaphroditic animals. |
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Keywords: | Gastropoda Hermaphrodite Mollusca Outcrossing Pulmonata Selfing |
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