Seasonal Changes of Serum Gonadotropin Levels and Effects of MT Implantation on GtH Secretion of Spotted -Longbarbel Catfish (Mystus guttatus)

The seasonal changes of GSI and serum gonadotropin(GtH) levels of spotted longbarbel catfish(Mystus guttatus Lacepede),and effect of 17α-methyl-testosterone(MT) implantation on GtH secretion were studied.Based on carp gonadotropin-β(cGtH-β) and its anti-serum(Rac),heterologous radio-immunoassay(RIA) for GtH of spotted longbarbel catfish was developed.These results showed gonadosomatic index(GSI) of female and male spotted longbarbel had the highest value in May and June,and was higher than those in other monthssignificantly(P0.05);Serum GtH levels of female and male spotted longbarbel catfish had the highest value in June,and was higher than those in other months(female in Oct and Dec,male in Apr,Oct and Dec) significantly(P0.05);The seasonal changes of serum GtH levels of male spotted longbarbel catfish were similar to those of female spotted longbarbel catfish,and no significant differences were observed among female fish with male fish in all months;MT implantation had effect on serum GtH levels of spotted longbarbel catfish,in early gonada development stage gonadal maturation and ovulation stage,MT implantation could increase serum GtH level of spotted longbarbel catfish,but in gonadal maturation and ovulation stage,MT implantation could decrease serum GtH level of spotted longbarbel catfish.These results indicated that MT implantation could have an effect on artificial propagation of spotted longbarbel catfish.