Life history traits of the sand stargazerDactyloscopus tridigitatus(Teleostei: Blennioidei) from south-eastern Brazilian coast

Abstract

Individuals of the sand stargazerDactyloscopus tridigitatuswere collected monthly over a period of one year in an urban-sandy beach in south-eastern Brazil. We sampled 57 males, 64 females, and 6 juveniles, indicating a sex-ratio of approximately 1:1. Total length and weight did not differ significantly between sexes, showing no sexual dimorphism in size. The growth ofD. tridigitatuswas highly positive allometric and the correlation coefficient was significant for both sexes. Males were observed carrying two egg clumps under each enlarged pectoral fin during most of the year. In contrast, females showed a more restricted reproductive period, concentrated during the austral rainy season. The number of eggs in each clump carried by males did not differ significantly from the number of vitellogenic oocytes of mature females. The number of eggs carried by males was weakly correlated to male total length; however, female fecundity was strongly correlated to female total length.Dactyloscopus tridigitatusconsumed a high variety of prey items, including crustaceans, annelids, molluscs, teleosts, insects and eggs. Isopods were the most important component of the diet followed by polychaetes and amphipods. We concluded that promiscuous breeding, paternal care behaviour and invertivorous feeding habits seem to be important traits for the species' success in the studied habitat.