Transient sex change in the immature Malabar grouper, Epinephelus malabaricus, androgen treatment.

To clarify the cause of sex change recovery after the withdrawal of androgen treatment, immature female Malabar grouper were fed a diet containing 17alpha-methyltestosterone (MT) at 50 μg/g for 7 mo and then a normal diet for 6 mo. The MT brought about precocious sex change from immature ovaries to mature testes with active spermatogenesis, including the development of spermatozoa, and sex change reversed soon after MT treatment withdrawal. This result indicates that precocious sex change in immature Malabar grouper with oral MT treatment is impermanent.

The role of pituitary gonadotropins in gonadal sex differentiation in the protogynous Malabar grouper, Epinephelus malabaricus.

The aim of this study was to clarify the roles of 2 gonadotropins (GTHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), on sex differentiation in the protogynous Malabar grouper, Epinephelus malabaricus. To do this, the mRNA expression patterns of GTH subunits (cga, fshb, and lhb) in the fish pituitary throughout gonadal sex differentiation were investigated. Real-time reverse transcriptase (RT)-PCR showed that cga and fshb were present in the undifferentiated and ovarian differentiation stages, and that the expression levels significantly increased after ovarian differentiation (AOD).

Differentiation of steroid-producing cells during ovarian differentiation in the protogynous Malabar grouper, Epinephelus malabaricus.

To understand the mechanism of sex differentiation in the protogynous Malabar grouper Epinephelus malabaricus, we performed an immunohistochemical investigation of the expression of three steroidogenic enzymes, cholesterol-side-chain-cleavage enzyme (CYP11a), aromatase (CYP19a1a), and cytochrome P45011beta-hydroxylase (CYP11b), in the gonads during ovarian differentiation. Strong positive immunoreactivity against CYP11a, the key enzyme of steroidogenesis, and CYP19a1a which is essential for estrogen (17beta-estradiol) production, appeared first in the somatic cells surrounding gonial germ cells in undifferentiated gonads and throughout ovarian differentiation. However, positive immunoreactivity against CYP11b, which is important for androgen (11-ketotestosterone) production, first appeared in the cluster of somatic cells in the ovary tunica near the dorsal blood vessel after differentiation.