Characterization of Pubertal Development Phases in Female Longtooth Grouper Epinephelus bruneus via Classification of Bodyweight

摘要

Puberty is the developmental period which animals obtain the ability of reproducing sexually for the first time in life. In commercially important aquaculture fish species, the onset of puberty is a matter of major interest due to controlling of sexual maturation to improve broodstock management. To investigate pubertal characteristics of female longtooth grouper (Epinephelus bruneus), specimens were classified into three groups by the bodyweight, including 1, 2, and 3 kg group. Thereafter, we focused on ovarian development and level changes of endocrine regulation factors (GnRH, GTHs, steroid hormone). In the non-breeding season (April), the levels of endocrine regulation factors showed increasing trends in accordance with bodyweight gaining; nevertheless, the oocytes were growth phase belongs to almost peri-nucleous stages in all groups. In the breeding season (June), the levels of endocrine regulation factors were fluctuated that decreases in levels of sbGnRH and FSHβ mRNA expressions along with serum E2 concentrations in 3 kg of group. However, LHβ mRNA expression levels sustained increasing trends by the bodyweight. Moreover, the oocytes developed that 2 kg and 3 kg groups obtained plentiful vitellogenic oocytes while 1 kg group was still composed with greater part of pre-vitellogenic oocytes. Especially, the oocytes of 3 kg group reached over 450 μm of diameters that indicating possibility to enter the final maturations. These results suggest that the progress of pubertal development in female E. bruneus could be classify into three phases via bodyweight, including pre-puberty (1 kg), early-puberty (2 kg) and puberty (3 kg).