The effect of thyroxine on the larvae and fry of Sarotherodon niloticus L. (Tilapia nilotica)

Abstract

Effects of thyroxine (T₄) (0.1 ppm; 0.3 ppm; 0.5 ppm) on Sarotherodon niloticus L. yolk sac larvae were studied after 4 weeks of treatment from hatching. T₄ at 0.5 ppm accelerated yolk resorption but did not significantly increase growth after the first week of treatment. Increase in length and in weight among fry treated with T₄ at 0.1 ppm and 0.3 ppm was significant after the fourth week. T₄ at 0.1 ppm increased significantly the length of the pectoral fin; but at 0.3 ppm and 0.5 ppm caused abnormal shapes in the pectoral fins as well as lordosis and scoliosis. T₄ reduced pigmentation in treated yolk sac larvae for 3 days only and caused thickening of the epidermis in both treated yolk sac larvae and fry. Thyroid follicles were absent in the yolk sac larvae but present in the fry.