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Abstract

Sequential hermaphroditism is widespread among teleosts and contains one of the most striking expressions of plasticity in sexual development: sex change [1]. Protogyny is more frequent among teleosts and individuals are initially females; later, in adulthood, the ovaries are replaced by testes, transforming them into reproductively active males, whereas in protandry, the reverse occurs [1]. This process is known as sex inversion. Hermaphrodite species of simultaneous type, which present ovaries and testes simultaneously, are also known, but less frequently. Sex inversion is a very successful reproductive strategy among fish [2] and species that present this reproductive strategy have evolutionary advantages, translated by a plasticity that can be triggered by different environmental conditions, such as socio-demographic modulations in the case of serranids [3]. Many hermaphrodite teleost species are under critical conservation status and to produce them successfully in captivity, it is necessary to know the reproductive physiology of these species and the environmental modulations that are relevant in this process. Individuals in a population have a system that receives information from the external environment (environmental signals) and internal organs (physiological events), integrates them, regulates them, and results in a neuroendocrine control, which in turn triggers all physiological events that will lead to successful reproduction [4].The majority of teleosts present the reproductive process modulated by environmental factors, such as temperature, photoperiod, rainfall, among other variables. However, the multiple and complex hormonal interactions between the sensory and reproductive organs, associated with the event of reproduction, are endogenously provided by an neuroendocrine system, involving primarily the hypothalamic-pituitary-gonadal (HHG) axis, which synthesizes and releases , gonadotropin releasing hormones (GnRHs), gonadotropins (GtHs), follicle stimulating hormone (FSH) and luteinizing hormone (LH), gonadal steroids (androgens, progestogens and estrogens). Neuromodulators also stimulate and / or inhibit this process (for example, dopamine, gonadotropin inhibiting hormone, gamma-aminobutyric acid, insulin-like growth factor, neuropeptide Y), among other substances [4]. Under suitable conditions for the animals, this whole process occurs naturally, with the development of the gonads, maturation, release and fertilization of the gametes, and in general, in teleosts, spawning and fertilization occur in the external environment. A permanent communication between the complex H-H axis and the peripheral organs (particularly the gonads) allows the synchronization of all the steps of the life cycle. In this case, of importance in the communication between the H-H axis and the gonads, are the sexual steroids, since they are indicators of the sexual status of vertebrates. These steroids can act in various tissues (such as the liver, pituitary, brain and gonad itself), altering the expression of neurohor...