Testicular maturation of thin-lipped grey mullet during the annual reproductive cycle in captivity

Abstract

ABSTRACTIntroduction: Continuous maintenance of mullet broodstock in captivity and the control of testicular development are important, particularly when linked to mass propagation of juveniles in the hatcheries, however, the complete description of testes maturation still lacking.Aim of the work: The main goal of our study to present a complete description for the testes and the obtaining of mature thin-lipped mullet, Liza ramada, males suitable for breeding in captivity.Material and methods: We performed morphological and histological techniques to describe the testicular cycle of developmental stages of male mullet reared in freshwater and captivity. Results: In general, the testes of L. ramada exhibit remarkable seasonal variations in shape, size, color and texture. Indeed, five developmental stages were characterized during testicular cycle in L. ramada in freshwater based on the histomorphology and gonadosomatic index. These stages include immature testis, stimulating spermatogenesis, rapid spermatogenesis, mature (ripe) testis and spawning (running) testis. Importantly, the testis development started when the day length and water temperature begun to decrease in September while the gradual decrease in both photoperiod and water temperatures ensure complete gonad maturation (September-December). However, induction of successful spawning in L. ramada occurs when photoperiod and water temperatures decline to their minimum values during December.Conclusion: The present study provides the morphological and histological description for testes of L. ramada during gonad maturaion in captivity and able to obtain a ripe mullet male suitable for hormonal induced reproduction in these species especially in captivity. In spite of attaining the ripe stage of L. ramada males in freshwater, the spawning can only possible with hormonal and environmental stimulation.