Flow cytometric sexing of spider sperm reveals an equal sperm production ratio in a female-biased species.
Producing equal amounts of male and female offspring has long been considered an evolutionarily stable strategy. Nevertheless, exceptions to this general rule (i.e. male and female biases) are documented in many taxa, making sex allocation an important domain in current evolutionary biology research. Pinpointing the underlying mechanism of sex ratio bias is challenging owing to the multitude of potential sex ratio-biasing factors. In the dwarf spider, Oedothorax gibbosus, infection with the bacterial endosymbiont Wolbachia results in a female bias. However, pedigree analysis reveals that other factors influence sex ratio variation. In this paper, we investigate whether this additional variation can be explained by the unequal production of male- and female-determining sperm cells during sperm production. Using flow cytometry, we show that males produce equal amounts of male- and female-determining sperm cells; thus bias in sperm production does not contribute to the sex ratio bias observed in this species. This demonstrates that other factors such as parental genes suppressing endosymbiont effects and cryptic female choice might play a role in sex allocation in this species.
Terrestrial Ecology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark bvthourn@biology.au.dk.
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Vanthournout
Laboratory of Immunoregulation and Mucosal Immunology, Department for Molecular Biomedical Research, VIB, Ghent 9050, Belgium.
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Deswarte
Laboratory of Immunoregulation and Mucosal Immunology, Department for Molecular Biomedical Research, VIB, Ghent 9050, Belgium.
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Hammad
Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark.
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Bilde
Laboratory of Immunoregulation and Mucosal Immunology, Department for Molecular Biomedical Research, VIB, Ghent 9050, Belgium.
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Lambrecht
Terrestrial Ecology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium Royal Belgian Institute of Natural Sciences, Vautierstraat 29, 1000 Brussels, Belgium.
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Hendrickx
D000818:Animals; D005260:Female; D005434:Flow Cytometry; D008297:Male; D012744:Sex Ratio; D013091:Spermatogenesis; D013094:Spermatozoa; D013112:Spiders
flow cytometry; sex ratio bias; sperm sexing; spider