The Key Hormone Change Pattern of Thyroid Hormone Axis and Growth Axis of Japanese flounder (Paralichthys olivaceus) in the Ponds

Abstract:

Enzyme-linked immuno sorbent assay was used to measure the serum L-thyroxine (T4), 3,5,3'-triiodo-L-thyronine(T3), growth hormone (GH), and insulin-like growth factor-I (IGF-I) in Japanese flounder (Paralichthys olivaceus) of three ponds. The seasonal variations of body weight and body length were found in present study. Body weight and body length increased constantly as time grows, which were higher in late summer and early autumn compared with other seasons. The average weight of three aquaculture ponds were 1341.77 g, 1198.20 g and 958.93 g and the average length were 54.22 cm, 45.33 cm and 39.40 cm after cultivation for 12 months. The seasonal variations of serum T4, T3, GH and IGF-I were observed. The highest level of the serum T4 was in late summer and the peak of the serum T3 level appeared in early autumn. The highest GH level existed in early summer. The peak level of IGF-I appeared in early autumn. These results revealed the close relationship among the water temperature, body length and body weight growth rate and the serum level of T4 and T3 and T4/T3 increased rapidly, however the potential mechanism need further study.