Courtship display increases exposure to parasites in the viviparous fish Xenoophorus captivus

Abstract

A central issue in sexual selection theory is to understand why there are female preferences for males displaying ornaments. One theory proposes that displaying male secondary sexual characters is costly, and that this reveals information about the male´s phenotypic quality. Here, we used the viviparous Xenoophorus captivus (Goodeidae), a fish whose males often remove the bottom sediments during courtship (substrate sweeping), to test the hypothesis that male courtship displays expose males to parasitic infection, and thus may convey relevant information on the quality of a mating partner. First, we evaluated the females preference for males that perform more and longer courtship displays. Then, we exposed courting males to the presence of ectoparasites while manipulating their opportunity to perform substrate sweeping. We found that males that were allowed to sweep the substrate became infected and, as a consequence, interrupted their displays and began scratching, resulting in shorter courtship bouts in comparison to males prevented from sweeping the substrate. Thus, the occurrence of substrate sweeping in this species allows females to determine whether a male is infected with skin parasites through assessing the length of his courtship bouts.