Reproductive behaviors and sex roles during a diurnal cycle of the goby, Lythrypnus pulchellus (Teleostei: Gobiidae)

Reproductive behaviors are a key factor to achieve successful spawning and fertilization in sexual species. Among harem polygynous site-attached reef fishes, relative size and sexual proportions may be determinant to establish hierarchies and sexual roles during reproductive behavior. In the present study the pattern of reproductive behavior (courtship, intrasexual competition and parental care) of the gorgeous goby, Lythrypnus pulchellus, a small cryptobenthic diurnal reef species endemic to the tropical eastern Pacific is described for the first time. We tested the plasticity of sex roles using two treatments, one biased towards males and one biased towards females. The influence of daylight on reproductive behaviors was also assessed. The characterization, frequency and duration of reproductive displays were obtained from video-recorded observations under laboratory captive conditions each day from 8:00 to 19:00 h for 10 min every hour over 5 days. Sixteen displays were identified, of which “Jerk”, “Nest Defense”, “Parental Care” and “Nipping” were exhibited only by males. “Nest Approach” and “Solicitation” were displayed only by females, and the remaining 10 behaviors were identified in both sexes. The apparent “rule” to form a social hierarchy among individuals of the more abundant sex was body size, with the largest becoming the dominant individual. Females courted more than males in both biased sex ratios experiments. Comparing the rate of courtship between males in the male-biased treatment with males in the female-biased treatment, it was evident that courtship rate was higher in the latter case. In the male-biased treatment, the rate of courtship was higher in the smaller (subordinate) male than in the larger (dominant) male. However, males and females are similar in competition in any of the biased sex ratio experiments. It leads to the conclusion that the gorgeous goby shows plasticity in their reproductive behaviors in response to OSR. The frequencies and durations of reproductive behaviors of both males and females decreased according to time of day in both biased sex ratio experiments, except for the courtship behaviors “Nest approach” in females and “Nest defense” in males that increases throughout the day. The elucidation of the plasticity of mating behaviors is relevant to understand the interactions in sequential hermaphrodite fishes as L. pulchellus.