Hermaphroditism in teleost fishes and their implications in commercial aquaculture

Abstract

The teleost fishes are the most diverse group of vertebrates and present a great variety in their reproduction form. Gonocorism is the most common form of reproduction among fish. However, a significant number of fish present hermaphroditism, that is, the same individual presents both sexes, simultaneously or sequentially. The point in time at which the sex change occurs is not necessarily instantaneous and can be interpreted at many different levels (by social, morphological and age behavior). The mechanisms of sexual determination and sexual differentiation are involved in this sex change and may be affected by the genetic inheritance or by the environmental changes in which an individual finds itself. The activity aromatase, estradiol, 11-ketotestosterone and testosterone are involved in the regulation of the reproductive process of hermaphroditic females and males. The pre-optic area (POA) and the hypothalamus are the two regions of the brain responsible for the control of the reproductive physiology and reproductive behavior of fish. Within the endocrine status of sequential hermaphroditic fish, great similarities with the endocrinology of gonochoric species are observed. Taming hermaphroditic species for reproductive purposes can bring great complications; the most common is to keep the desired sex ratio constant, therefore, the control of sex is a priority. To achieve this, it is necessary to know the reproductive physiology of the selected species and implement some strategy to manipulate this sex change, either through social factors or hormonal therapies.