Growth and sex differentiation relationship in the European sea bass (Dicentrarchus labrax)

Abstract

Phenotypic sex is the result of the processes of sex determination (genetic or environmental) [1] and sex differentiation [2], and is highly labile in fish, since in several species it is affected by environmental factors such as temperature, pH or density. The European sea bass (Dicentrarchus labrax) is a gonochoristic species where its polygenic sex determination mechanism [3] is influenced by temperature [4]. Growth dimorphism is present in teleost fish, but while in some species males are the largest fish [5] in others, such as the European sea bass, females are larger than males [3, 6, 7, 8]. A correlation between growth and final sex has been found in studies where size-grading of sea bass populations applied at the early stages of development generated two well differentiated populations: one female-dominant population (the largest fish) and one male-dominant (the smallest fish) [9]. It has been suggested that gonadal differentiation is dependent on whether a certain size is reached by a certain developmental time [10, 11], suggesting that early growth is the factor controlling sex. However, in fish it has been also observed that growth can depend on phenotypic rather than genotypic sex [8, 12], which would suggest that is the course of sex differentiation that determines early growth. The objective of this study was to investigate these two alternative possibilities in the European sea bass