Sperm release and use at fertilization by yellow dung fly females (Scathophaga stercoraria)

Females of many species mate multiple times and store transferred sperm in storage organs. The mechanisms underlying sperm release from the stores at fertilization remain poorly understood, although they are central to an understanding of the female influence on post-copulatory male competition. Usi...

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Bibliographic Details
Published in:Biological journal of the Linnean Society 2009-11, Vol.98 (3), p.511-518
Main Authors: SBILORDO, SONJA H, SCHÄFER, MARTIN A, WARD, PAUL I
Format: Article
Language:English
Subjects:
Biological and medical sciences
Biological evolution
Competition
cryptic female choice
Fundamental and applied biological sciences. Psychology
Genetics of eukaryotes. Biological and molecular evolution
Insecta
Invertebrates
Scathophaga
Scathophaga stercoraria
Scatophaga
sperm competition
sperm displacement
sperm loss
sperm storage
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Summary:Females of many species mate multiple times and store transferred sperm in storage organs. The mechanisms underlying sperm release from the stores at fertilization remain poorly understood, although they are central to an understanding of the female influence on post-copulatory male competition. Using double-mated females of the yellow dung fly, we counted the sperm sticking to the surface of deposited eggs of two successive clutches to obtain insight into the physiological processes associated with fertilization. The number of sperm released to fertilize an egg decreased between the first and second clutches, as well as within clutches from early to late eggs. These results indicate that: (1) sperm are lost from the stores over time independent of egg laying and (2) the number of sperm released depends on the amount of sperm stored. The lower number of sperm on eggs of the second clutches was accompanied by a strong increase of the proportion of sperm adhering to the micropyle region, suggesting that sperm use is more efficient and sperm release better controlled when sperm supply is substantially reduced. Finally, our approach indicates that sperm storage capacity of the female is higher than assumed from counts of spermathecal sperm.
ISSN:0024-4066
1095-8312
DOI:10.1111/j.1095-8312.2009.01296.x