Seleção sexual em Aegla longirostri (Decapoda: Anomura): escolha de parceiro, meios de comunicação e efeitos na agressividade

Abstract

This study involved two experiments that addressed mate choice, male competition for mature females and the communication pathways used by both sexes in Aegla longirostri. In the first experiment, males were paired according to body and cheliped size, and they were acclimated in the laboratory for a week. Next, they were accommodated in opposite sides of an aquarium that was divided in three parts. A container with a female inside was inserted in the center of the aquarium, according to four treatments: Fimat, perforated and translucent container holding an immature female (N = 10); FmatCV, the same container holding a mature female (N = 10); FmatV, translucent and non-perforated container holding a mature female, (N = 10); FmatC, perforated opaque container with a mature female (N = 10); NF = no female in the container. Afterwards, the males were released and left interacting for 20 min. The following variables were quantified: time of the first three bouts, time spent in aggressive acts, latency period, time that animals remained near the container and the number of antennal whips per bout second. Thus, we observed that males fight more quickly and less intensely in the presence of mature females, independently of the communication pathway used. However, both stimuli were needed to elicit a guarding behavior by the winner. Therefore, the female might be controlling the cues that advertise her receptivity, only releasing them when the preferred male is near. This causes information asymmetry between the males, which makes shorter fights. We also demonstrated the importance of bimodal stimuli (chemical + visual) for reproductive behaviors, since the behavioral repertory presented was more complex when both could be used. To assess mate choice in A. longirostri, we used a different experimental design. Animals were grouped in triads, two of them were used as choices ( targets ) and one as the choosing individual ( focal ). They were accommodated in a Y-maze in four different treatments: MD, adult male as focal animal and two females, one immature and one mature as targets (N = 8); FD, mature female as focal animal and two adult males, a large male and a smaller one as targets (N = 7); Q, like FD but the female could choose based only in chemical cues provided by the targets (N = 7); F, like FD but the female could choose based only in visual cues (N = 7). The eglids were acclimated for 10 min and then the focal animal was released for 20 min. We quantified the time spent in the corridor as an index of preference. Males did not choose between females, however the time spent in the mature female corridor was highly variable. On the other hand, the females only chose the large males when they could assess them through visual and chemical stimuli. Thus, females may control the release of cues that advertise her receptivity, and so, only preferred males could actually make the choice. The females may also need more information to choose between potential mates, since they only showed preference when two stimuli were present.