Effect of Dietary Thyroxine Supplementation to Brood Nsh on Early Larval Development of Climbing Perch, <i>Anabas testiidineus</i>

Abstract

Effect of dietary thjroxine (T4) supplementation to Anabas testudineus brood fish on growth of their larvae were evaluated. The brood fish were divided into four groups - one group was fed with control diet and rest three groups were fed with 2 mg T4/kg diet, 5 mg T^/kg diet and 10 mg T^/kg diet, respectively for a period of 4 weeks. After 4 weeks, the fish were induced to breed using Ovaprim and the larvae were reared separately for a period of two weeks. The results indicated that larvae of T4 treated spawners exhibited significant increase in growth and also tended to show better survival compared to larvae of control group spawners. When larvae of control and T4 treated spawners were reared in thyroid hormone containing rearing medium (0.05 ppm), it was indicated that T4 at 0.05 ppm accelerated growth in larvae of control spawners and consistently, the same did not induce growth increment in the case of T4 treated spawners larvae. Hence, it was considered that in the case of T4 treated spawners, there might be transfer of thyroid hormone from mother to the oocytes and subsequently to the larvae and further treatment through immersion might have resulted in over dose of thyroid hormone leading to thyrotoxicosis and thereby growth retardation.