Seasonal sex role changes in the blenniid Petroscirtes breviceps, a nest brooder with paternal care

Abstract

The plasticity of the sex roles in the blenniid fish Petroscirtes breviceps, a nest brooder with exclusive paternal care, was studied throughout an 8 month breeding season. Males performed most courtships early and late in the breeding season, whereas females performed most in the middle of the season. These results indicated that the sex of individuals initiating courtship changed seasonally, with courtship role reversal in the middle of the season. Intrasexual aggression in both sexes occurred much more frequently in mid-season than in the early and late seasons. Males frequently fought when available nest sites were limited, regardless of the presence of females, suggesting that males competed for nests in order to qualify to mate (resource competition). In contrast, courting females fought only in mid-season, when females' relative success in entering nests decreased, indicating that females competed for limited mating opportunities (mating competition). The reversed courtship roles and female mating competition in mid-season suggested that the sex roles in P. breviceps changed seasonally from the conventional roles to reversed roles and back again during one breeding season. This study provides the first empirical evidence of multiple changes in the sex roles of animals within a breeding season.

Male Isaza (Gymnogobius isaza, Gobiidae) prefer large mates: a counterstrategy against brood parasitism by conspecific females

“…Thus, the days during which spawning females remain in the nests might be the period during which nests are most vulnerable to additional spawning by other females. It is often reported that in many nest-brooding fish with exclusive paternal care, males attack females immediately after spawning, and the females leave the nests (Takahashi and Yanagisawa 1999;Yanagisawa 2000, 2003;Shibata and Kohda 2006;Gomagano and Kohda 2007). In fishes exhibiting exclusive paternal care, males in general do not repel further females from approaching to spawn.…”

“…Destruction of the brood provides an opportunity for parasitic females to mate with the guarding male (Ichikawa 1990(Ichikawa , 1991(Ichikawa , 1993. Another example of brood parasitism with forcible spawning is in the wood duck Aix sponsa, which may have female-biased operational sex ratios, as limited numbers of wood-cavity nests restrict the number of males available (qualified to mate, Forsgren et al 1996;Shibata and Kohda 2006), whereas many females that do not have nests can produce eggs (Sherman 2001). Thus, in some pair nests, a number of eggs are spawned parasitically beyond the brooding capacity, and eventually all eggs die in many nests because of insufficient brood incubation (Sherman 2001).…”

“…Males of these fish exclusively care for eggs (e.g., fanning and mouthing), and increase their fitness (i.e., the number of hatching eggs) by mating with large and numerous females within a breeding cycle (Rohwer 1978;Barlow 1991;Lindström and Hellstrom 1993;Forsgren et al 1996;Takahashi et al 2001;Shibata and Kohda 2006;Gomagano and Kohda 2007). In general, fish exhibiting exclusive paternal care have polygamous mating systems (Kuwamura 1984(Kuwamura , 1997Barlow 1991;Belles-Isles and FitzGerald 1991).…”

Interpopulational variation of the mating system in the peacock blenny Salaria pavo

“…Together with the sex roles, so does the intrasexual competition shift from male-male to female-female to male-male. This is explained by a decrease in available nests along the season, reaching a critical point at the peak of the breeding season, and by a gradual increase in the number of available nests towards its end (Shibata and Kohda 2006).…”

“…The balance between the potential reproductive rates of each sex predicts the sex with the higher level of intrasexual competition Clutton-Brock and Vincent 1991). As an example, Shibata and Kohda (2006) report for the blenny Petroscirtes breviceps (Valenciennes) a change in sex roles from typical (i.e. males court females) at the beginning of the breeding season to reversed (i.e.…”