Intraspecific variation in ejaculate traits of the northern watersnake (Nerodia sipedon)

摘要: Sperm competition occurs when the sperm of more than one male compete to fertilize eggs a female. In reptiles, is particularly prevalent and an important agent sexual selection in males. Spermatogenesis reptiles can be energetically expensive, suggesting that there may costs producing high-quality ejaculates. The northern watersnake Nerodia sipedon has mating system characterized by aggregations which single female mates with multiple males, resulting high levels paternities. Under these circumstances likely important, should favour ejaculate traits enhance male's reproductive success. this study, we examined intraspecific variation quality (sperm length, motility, density, spermactocrit) watersnakes determined whether varied body size condition, using both size-corrected mass haematocrit as indices condition. We found large among males all traits, except for length. Although was significant length majority occurred within rather individuals. Males had were less variable respect produced ejaculates concentrated small lack condition dependence most consistent previous studies indicate effort species generally not energy limited, perhaps because opportunistic foraging during season.