Friesen Christopher R, Powers Donald R, Copenhaver Paige E, Mason Robert T
School of Biological Sciences, University of Sydney, Heydon-Laurence Bldg AO8, Science Rd, Sydney, NSW 2006, Australia Department of Zoology, Oregon State University, Cordley Hall 3029, Corvallis, OR 97330, USA
Department of Biology, George Fox University, Edwards-Holman Science Center, Newberg, OR 97132, USA.
J Exp Biol. 2015 May;218(Pt 9):1410-8. doi: 10.1242/jeb.120402.
The non-sperm components of an ejaculate, such as copulatory plugs, can be essential to male reproductive success. But the costs of these ejaculate components are often considered trivial. In polyandrous species, males are predicted to increase energy allocation to the production of non-sperm components, but this allocation is often condition dependent and the energetic costs of their production have never been quantified. Red-sided garter snakes (Thamnophis sirtalis parietalis) are an excellent model with which to quantify the energetic costs of non-sperm components of the ejaculate as they exhibit a dissociated reproductive pattern in which sperm production is temporally disjunct from copulatory plug production, mating and plug deposition. We estimated the daily energy expenditure and resting metabolic rate of males after courtship and mating, and used bomb calorimetry to estimate the energy content of copulatory plugs. We found that both daily energy expenditure and resting metabolic rate were significantly higher in small mating males than in courting males, and a single copulatory plug without sperm constitutes 5-18% of daily energy expenditure. To our knowledge, this is the first study to quantify the energetic expense of size-dependent ejaculate strategies in any species.
射精产物中的非精子成分，如交配栓，对雄性的繁殖成功可能至关重要。但这些射精产物成分的成本通常被认为微不足道。在一妻多夫制物种中，预计雄性会增加对非精子成分产生的能量分配，但这种分配通常取决于身体状况，而且其产生的能量成本从未被量化过。红边束带蛇（Thamnophis sirtalis parietalis）是一个很好的模型，可用于量化射精产物中非精子成分的能量成本，因为它们表现出一种分离的繁殖模式，即精子产生在时间上与交配栓产生、交配和栓的沉积相分离。我们估计了求偶和交配后雄性的每日能量消耗和静息代谢率，并使用弹式量热法估计交配栓的能量含量。我们发现，小型交配雄性的每日能量消耗和静息代谢率均显著高于求偶雄性，且一个不含精子的交配栓占每日能量消耗的5 - 18%。据我们所知，这是第一项量化任何物种中与体型相关的射精策略能量消耗的研究。
