Jd. Tanfermin et al., INDUCTION OF SEX INVERSION IN JUVENILE GROUPER, EPINEPHELUS-SUILLUS, (VALENCIENNES) BY INJECTIONS OF 17-ALPHA-METHYLTESTOSTERONE, Gyoruigaku Zasshi, 40(4), 1994, pp. 413-420
Four groups of two-year old juvenile groupers (Epinephelus suillus), e
ach with 8-9 individuals of mean body weight (BW) 1.2 kg, were treated
with 17alpha-methyltestosterone (MT). MT was injected intramuscularly
within the range of 0.5-5.0 mg kg-1 BW every 15 days. Gonadal biopsy
and stripping of the abdomen was done every 15 days, the fish being sa
crificed after six or twelve injections. Initial controls had immature
ovaries containing primary oocytes in lamellae that extended into the
central lumen. After six injections, proliferation of stromal and gon
ial cells were observed in all fish sampled. Regardless of treatment,
gonad sections of fish with a minimum BW of 1.2 kg showed degeneration
of primary oocytes and the presence of spermatogenic cells. Milt was
also present in larger-sized fish (BW: 1.5 kg) given 0, 0.5 and 1.0 mg
MT kg-1 BW, after such fish had received an accumulated dose of 5 or
12 mg MT kg 1 BW. However, gonad sections of smaller-sized fish follow
ing these treatments contained only primary oocytes and gonial cells a
fter six (BW: 0.7-1.0 kg) or twelve (BW: 0.6-1.3 kg) injections. In co
ntrast, all fish treated with 5 mg MT kg-1 BW had testes in active spe
rmatogenesis after six (BW: 1.2-1.6 kg) or twelve (BW: 0.8 kg) injecti
ons. Gonad weight and gonadosomatic index values decreased during cons
ecutive sampling. Induction of female-to-male sex inversion in juvenil
e E. suillus by MT was probably synergistic with age and size.