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- Ah-King, M., et al.
(författare)
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Why is there no sperm competition in a pipefish with externally brooding males? Insights from sperm activation and morphology
- 2006
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 68:3, s. 958-962
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Tidskriftsartikel (refereegranskat)abstract
- Nerophis ophidion sperm activation and morphology were investigated with the aim of explaining the apparent lack of sperm competition in this syngnathid with externally brooding males. Nerophis ophidion sperm were activated by a mixture of ovarian fluid and sea water, but not by sea water alone. This indicated that sperm were not shed into the water but needed to be released near the eggs, which probably restrained sperm competition. (c) 2006 The Fisheries Society of the British Isles.
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- Aronsen, T., et al.
(författare)
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The operational sex ratio and density influence spatial relationships between breeding pipefish
- 2013
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 24:4, s. 888-897
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Tidskriftsartikel (refereegranskat)abstract
- The operational sex ratio (ratio of sexually receptive males to females) has been extensively studied in behavioral ecology, whereas other demographic factors such as the effect of density on mating behavior have received less empirical attention. We manipulated mating competition by establishing breeding populations of the sex-role reversed broad-nosed pipefish (Syngnathus typhle) at 2 sex ratios (male biased or female biased) and 2 densities. We used mean crowding (m*) and the index of association (X) to measure spatial distributions within and between the sexes, respectively, and investigated how these measures reflect the predicted strength of mating competition. In general, female m* increased as fewer males were available for mating, which suggests increased intrasexual competition in the most competitive sex. However, male m* also increased as the operational sex ratio became more female biased, suggesting that m* did not reflect mating competition for males. Association between the sexes (X) was higher under male bias than female bias, probably because males were still available for mating under male bias. In addition, X decreased in the female-biased treatment as the operational sex ratio became even more female biased. Higher density increased m* in both sex ratios and sexes, although for both sexes in the female-biased high-density treatment the operational sex ratio did not influence m*, probably because femalefemale competition inhibits further crowding in this treatment. In this study, we show that the use of m* and X can be a useful tool in behavioral studies but their interpretation requires detailed information about the mating system. Therefore, we recommend caution with their broadscale application.
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- Roth, O., et al.
(författare)
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Male mate choice relies on major histocompatibility complex class I in a sex-role-reversed pipefish
- 2014
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 27:5, s. 929-938
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Tidskriftsartikel (refereegranskat)abstract
- Mate choice for compatible genes is often based on genes of the major histocompatibility complex (MHC). Although MHC-based mate choice is commonly observed in female choice, male mate choice remains elusive. In particular, if males have intense paternal care and are thus the choosing sex, male choice for females with dissimilar MHC can be expected. Here, we investigated whether male mate choice relies on MHC class I genes in the sex-role reversed pipefish Syngnathus typhle. In a mate choice experiment, we determined the relative importance of visual and olfactory cues by manipulating visibility and olfaction. We found that pipefish males chose females that maximize sequence-based amino acid distance between MHC class I genotypes in the offspring when olfactory cues were present. Under visual cues, large females were chosen, but in the absence of visual cues, the choice pattern was reversed. The use of sex-role reversed species thus revealed that sexual selection can lead to the evolution of male mate choice for MHC class I genes.
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