Behaviour 2019
Sperm Competition Investment in Weaponless Males
James C Boothroyd, Steven M Smit, Sam Zlotnik, Christine W Miller. University of Florida, Gainesville, FL, United States

Males of many animal species invest considerable energy and resources into growing and maintaining weapons used to compete for access to mates. If females mate with multiple males, this competition can also extend to competition between ejaculates to fertilize eggs. Because both weapons and sperm production are energetically expensive, there is an expected tradeoff between them. In the leaf-footed cactus bug, Narnia femorata (Hemiptera: Coreidae), male testes size increases upon the removal of a weaponized hind leg. However, it is not yet known if investment in testes increases additively with the removal of both weapons, or if testes size reaches a maximum and resources are reallocated to other tissues instead. In the present study, males were prohibited from investing in their weapons at all, by inducing natural limb loss without regeneration at the penultimate juvenile stage. We then measured body size, area and length of the remaining weapon(s), and dry testes mass. This work furthers our understanding of reproductive investment in pre- and postcopulatory processes.