Multiple mating, sperm storage and internal fertilisation enhance sperm storage and internal fertilisation enhance sperm competition. The great pond snail can use stored sperm fro 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-fertlised. We aso 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 ins torage. To gain further insight into the mechanisms underlying the process of sperm storage, digestion andutilisation, we investigated the fate of donated sperm at different times after copulation. WE find that within 3 h after ransfer most sperm ave been transported into teh sperm-digesting organ. Flurescent labeling of sperm in histological sections further rveals that allosperm are not stored in the feritlisation puch, but upstream in either the hermaphrodictic duct, seminal vesicles, or ovotestis. Besides contributing to teh understanding of the mechanisms underlying sperm competition and/or cryptic sperm choice, this study shows that mixed mating cannot be treated as separate issue in hermaphroditic animals.
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