Ogden Hannah J P, de Boer Raïssa A, Devigili Alessandro, Reuland Charel, Kahrl Ariel F, Fitzpatrick John L
Department of Zoology: Ethology, Stockholm University, Svante Arrhenius väg, Stockholm, Sweden.
Behav Ecol. 2020 Jan-Feb;31(1):63-72. doi: 10.1093/beheco/arz156. Epub 2019 Sep 27.
Male mate choice occurs in a wide range of species, and males can increase their reproductive success by distinguishing between females based on their fecundity (e.g., large body size) or their expected sperm competition risk (e.g., virgins). However, patterns of male mate choice could be mitigated by variation in female physiological receptivity, as males can benefit by directing their mating efforts toward females that are at a point in their reproductive cycle when fertilization probability is highest. Here, we perform three experiments to assess whether male mate choice is influenced by cues of female physiological receptivity, fecundity, or sperm competition risk in the pygmy halfbeak (), a small livebearing fish. Female halfbeaks possess a "gravid spot"-an orange abdominal marking that is caused by pigmentation of the females' skin and variation in embryo development and pigmentation during pregnancy. We show that gravid spot size increases toward parturition and is largest right before giving birth, independent of abdominal width or body size. Males consistently chose females with large gravid spots over females with small gravid spots. In contrast, males did not prefer larger females over smaller females or virgin females over mated females. As female halfbeaks store sperm prior to fertilizations, we suggest that males use the size of the gravid spot as a cue to direct their mating efforts to those females where the chance of fertilization is highest.
雄性配偶选择在广泛的物种中都有发生，雄性可以通过根据雌性的繁殖力（例如体型较大）或预期的精子竞争风险（例如处女雌鱼）来区分雌性，从而提高自己的繁殖成功率。然而，雄性配偶选择模式可能会因雌性生理接受度的变化而受到影响，因为雄性若将交配努力指向处于繁殖周期中受精概率最高阶段的雌性，会从中受益。在此，我们进行了三项实验，以评估雄性配偶选择是否受到侏儒半颌鱼（一种小型卵胎生鱼类）雌性生理接受度、繁殖力或精子竞争风险线索的影响。雌性半颌鱼有一个“孕斑”——腹部的橙色斑纹，这是由雌性皮肤色素沉着以及孕期胚胎发育和色素沉着变化引起的。我们发现，孕斑大小在临近分娩时会增大，且在分娩前最大，与腹部宽度或体型无关。雄性始终会选择孕斑大的雌性而非孕斑小的雌性。相比之下，雄性并不偏好体型大的雌性而非体型小的雌性，也不偏好处女雌鱼而非已交配的雌鱼。由于雌性半颌鱼在受精前会储存精子，我们认为雄性利用孕斑大小作为线索，将交配努力指向受精几率最高的雌性。
