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

Sbilordo, Sonja H.; Schäfer, Martin A.; Ward, Paul I.

doi:10.1111/j.1095-8312.2009.01296.x

Cited by 15 publications

(10 citation statements)

References 40 publications

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“…In contrast, in insects and other invertebrates with internal fertilization, longer (or larger) sperm have been shown to have a competitive fertilization advantage against shorter (or smaller) sperm of rival males through enhanced displacement or other competitive abilities (13,20,30,31). In insects, sperm are stored at high density in the female sperm-storage organs (13,32), which in Drosophila have fixed volume so that new ejaculates displace previously stored sperm. At fertilization, sperm compete at high density around the proximal region of the sperm store duct to enter the micropyle of the egg as it passes down the oviduct.…”

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confidence: 99%

Resolving variation in the reproductive tradeoff between sperm size and number

Immler

Pitnick

Parker

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

170

208

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Spermatozoa are amongst the most variable cells, and three factors are thought to account for this variation in design: fertilization mode, phylogeny, and postcopulatory sexual selection. In addition, it has long been assumed that a tradeoff exists between sperm size and number, and although postcopulatory sexual selection affects both traits, empirical evidence for a tradeoff has so far been elusive. Our recent theoretical model predicts that the nature of a direct tradeoff between sperm size and number varies with sperm competition mechanism and sperm competition risk. We test these predictions using a comparative approach in two very different taxa with different sperm competition mechanisms: passerine birds (mechanism: simple raffle) and Drosophila fruit flies (sperm displacement). We show that in both groups, males increase their total ejaculate investment with increasing sperm competition risk, but whereas passerine birds allocate disproportionately to sperm number, drosophilids allocate disproportionately to sperm size. This striking difference between the two groups can be at least partly explained by sperm competition mechanisms depending on sperm size relative to the size of the female reproductive tract: in large animals (passerines), sperm numbers are advantageous in sperm competition owing to dilution inside the female tract, whereas in small animals (drosophilids), large sperm are advantageous for physical competition (sperm displacement). Our study provides two important results. First, we provide convincing evidence for the existence of a sperm size–number tradeoff. Second, we show that by considering both sperm competition mechanism and dilution, can we account for variation in sperm size between different taxa.

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confidence: 99%

Resolving variation in the reproductive tradeoff between sperm size and number

Immler

Pitnick

Parker

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

170

208

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“…All copulations took place in the absence of dung to avoid premature oviposition. One hour after the last mating (allowing sperm to move into storage: Sbilordo, Schäfer & Ward ; Bussière et al . ), females were provided with a smear of fresh dung on filter paper for oviposition.…”

Section: Methodsmentioning

confidence: 99%

The developmental plasticity and functional significance of an additional sperm storage compartment in female yellow dung flies

et al. 2013

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Summary1. The mechanistic basis for and adaptive significance of variation in female sperm storage organs are important for a range of questions concerning sexual selection and speciation, as such variation influences the evolutionary trajectories of male fertilization related traits and may facilitate speciation through its effects on gamete recognition. 2. Female yellow dung flies (Scathophaga stercoraria) usually develop three sperm storage compartments, and this subdivision may be an adaptation for sorting sperm during postcopulatory choice. 3. Using lines artificially selected to express four spermathecae (4s), we explored the fitness consequences of the novel phenotype relative to the naturally prevalent three-spermatheca (3s) phenotype by manipulating the opportunity for postcopulatory sexual selection (females mated either with three or only one male prior to oviposition). In addition, we examined the developmental plasticity of spermathecal number in response to different larval food environments and estimated its genetic correlation with growth rate. 4. Mating treatments with and without the opportunity for postcopulatory sexual selection revealed no significant fitness differences between alternative spermathecal phenotypes within selection lines despite overall benefits associated with multiple mating, and moderate egg-toadult survival costs in response to artificial selection for 4s. Manipulations of the larval food environment revealed that the expression of 4s is highly plastic and tightly linked to environmental conditions promoting fast somatic growth and development. Likewise, siblings with fast intrinsic (genetic) growth were more likely to express 4s within and across food environments. 5. The present results highlight a great potential for rapid evolutionary change in female sperm storage morphology through indirect selection on life-history traits, and further suggest genetic assimilation as a potential mechanism facilitating phylogenetic transitions in spermatheca number as frequently observed within the Dipterans.

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“…In a more positive and intriguing sense, temperature‐induced differences in reproductive morphology may promote local adaptation to changing environments by facilitating assortative mating among ecologically segregating demes (Kondrashov and Kondrashov 1999; Ritchie 2007). We here investigated the putative role of temperature in shaping and maintaining large‐scale geographic variation in the polymorphic female sperm storage organ of the yellow dung fly, Scathophaga stercoraria , arguably one of the best studied systems for postcopulatory sexual selection (e.g., Parker and Simmons 1994; Otronen et al 1997; Simmons et al 1999; Ward 2000; Hosken et al 2001; Sbilordo et al 2009; Bussiere et al 2010; Thüler et al 2011).…”

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confidence: 99%