[G] Oral presentations in English

[G-12] Leg-biting male combat between giant mealworm decrease loser’s fitness

◯Teruhisa Matsuura¹, Takahisa Miyatake¹ (1. Okayama Univ.)

Male combats are observed in many species. Often, the outcome of male combat affects the outcome of subsequent combats, mating success, number of sperm, and fitness of the male’s offspring. Also, the quantity of sperm may be regulated by winning or losing, depending on species ecology and mating system. However, few studies have experimentally examined the influence of fight outcomes on male offspring fitness. We studied male combat in the giant mealworm (Zophobas atratus) in which males bite each other’s hind legs. Therefore, we hypothesized that subsequent fitness could differ between winners and losers in the escalated male combat of this species. Thus, we measured several fitness traits including mating duration, the number of eggs laid by mated females, and the number of hatches sired by uncontested males, winners, and losers in escalated and non- escalated combat, and compared the fitness of each winner and loser to that of an uncontested male. As the result, only the loser‘s numbers of hatches in the escalated combat were greatly reduced compared to that of the uncontested males. This reduction may be due to injuries from escalated leg- biting fights and it may be due to the evolution of the winner male in response to the increased number of sperm by the loser male.