Overview on reproduction of teleosteal fish: from anatomy to molecular signaling

Abstract

One of the main goals of reproduction and fish is the production of a large number of viable gametes and high survival of offspring. In recent years, significant progress has been made in improving the efficiency of gametes production and progeny viability. However, there are still important gaps in the understanding of the physiological dynamic processes associated with gametogenesis. The knowledge of the structures that make up the gonads, as well as the all the neuroendocrine and molecular signaling mechanisms are of extreme importance in the elaboration of fish reproductive protocols. Among the challenges encountered, we highlight the wide range of fish species of different families, which, in most cases, have species-specific physiological mechanisms. In the neuroendocrine mechanism of fish reproduction, gonadotrophin releasing hormone (GnRH) is a neurotransmitter produced and secreted by the hypothalamus, which acts as a stimulatory factor on the release of LH and, to a lesser degree, FSH. Gonadotropic hormones (FSH and LH) act as the main regulators during vitellogenesis and maturation of gametes. It was believed that melatonin would be involved in the neuroendocrine mechanism in response to the photoperiod, inhibiting the release of GnRH. Recently, studies have shown that melatonin is also acting to accelerate the action of the maturation inducing hormone (MIH) and, consequently, the recovery of the meiotic cell cycle in carp. Thus, the objective of this review is to clarify the physiological mechanisms of the reproduction of teleosteos fish, starting from the description of the morphology of the gonads, understanding the neuroendocrine mechanisms and the molecular signaling