Impact of varying adult sex ration on temporary female ornamentation in pomatoschistus minutus

Abstract

The sand goby (Pomatoschistus minutus) is a small, sexually dimorphic fish species in which males typically exhibit colorful nuptial coloration and courtship behaviors to attract mates, while females often exhibit less conspicuous traits. However, one conspicuous but temporary trait is the dark eye display, a behavior in which females display a dark patch near their eyes, usually associated with spawning. The aim of this study was to investigate the impact of varying adult sex ratio on the frequency, duration, and latency of the dark eye display in female sand gobies. Two treatments with different adult sex ratios (male bias: 3 females and 4 males; female bias: 3 females and 2 males) were used, but no significant relationship was found between sex ratio and the frequency, duration, or latency of the display. However, positive correlations were found between relative female roundness and the occurrence of the display and between nest quality and the occurrence of the display. These results suggest that female sand gobies may use the dark eye display to signal their intent to mate, possibly responding to male courtship behavior. These findings provide insights into the role of female ornamentation and courtship behavior in the reproductive ecology of sand gobies and highlight the importance of considering a flexible approach when studying sexual selection and mate choice in animal populations. Further research is needed to explore the underlying mechanisms driving these relationships, their adaptive function, and potential implications for the evolution and ecology of sand goby populations.