Phenotypic plasticity in genitalia: baculum shape responds to sperm competition risk in house mice

Males are known to adjust their expenditure on testes growth and sperm production in response to sperm competition risk. Genital morphology can also contribute to competitive fertilisation success but whether male genital morphology can respond plastically to the sperm competition environment has received little attention. Here, we exposed male house mice to two different sperm competition environments during their sexual development and quantified phenotypic plasticity in baculum morphology. The sperm competition environment generated plasticity in body growth. Males maturing under sperm competition risk were larger and heavier than males maturing under no sperm competition risk. We used a landmark-based geometric morphometric approach to measure baculum size and shape. Independent of variation in body size, males maintained under risk of sperm competition had a relatively thicker and more distally extended baculum bulb compared with males maintained under no sperm competition risk. Pl...

众所周知，雄性个体可依据精子竞争风险，调整其在睾丸生长与精子生成方面的资源投入。生殖器形态同样可影响竞争性受精成功率，但目前针对雄性生殖器形态能否随精子竞争环境发生可塑性响应的研究仍较为匮乏。本研究将处于性发育阶段的雄性家鼠暴露于两种不同的精子竞争环境中，并量化了阴茎骨（baculum）形态的表型可塑性。精子竞争环境对雄性的身体生长产生了可塑性影响：处于精子竞争风险环境下发育成熟的雄性个体，其体型与体重均显著高于无精子竞争风险环境下发育的雄性个体。本研究采用基于标记点的几何形态测量法（landmark-based geometric morphometric approach），对阴茎骨的大小与形态进行了量化分析。在排除体型差异的干扰后，处于精子竞争风险环境中的雄性个体，其阴茎骨球相较于无精子竞争风险环境下的雄性个体更为宽厚，且远端延伸程度更高。Pl...