Thyroid hormone deficiency in abnormal larvae of the Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> |
| |
| Authors: | Email author" target="_blank">Nozomi?OkadaEmail author Tetsuo?Morita Masaru?Tanaka Masatomo?Tagawa |
| |
| Institution: | Hokkaido Central Fisheries Experimental Station, Yoichi, Hokkaido 046-8555,; Obama Station of National Center for Stock Enhancement, Fisheries research agency, Fukui 917-0117 and; Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606–8502, Japan |
| |
| Abstract: | ABSTRACT: In large-scale rearing of juveniles of the Japanese flounder Paralichthys olivaceus, a certain morphological abnormality occurred spontaneously in 4% of the fish. These fish showed a slight but clearly different appearance from any developmental stage of this species, and did not settle when all the other juveniles in the same tank completed metamorphosis and had settled. From comparisons of external and internal structures between the normal and the abnormal fish, the abnormality was attributed to unbalanced progress of metamorphosis, mainly due to metamorphic stasis. The thyroid of the abnormal fish was apparently activated morphologically. In addition, serum thyroxine (T4) concentrations in the abnormal fish were reduced to less than 1/10 of that of normal fish. After 14 days of T4 treatment (0.1 p.p.m) of the abnormal fish, all the abnormal characteristics disappeared, and the fish recovered to normal, suggesting normal responsiveness to thyroid hormones in peripheral tissues, whereas thiourea treatment (30 p.p.m., 14 days) further delayed metamorphosis. These results suggest that these abnormal fish were suffering from thyroid hormone deficiency, and were unable to secrete a sufficient amount of thyroid hormone to complete metamorphosis. |
| |
| Keywords: | abnormal fish Japanese flounder metamorphosis thyroid hormone |
| 本文献已被 SpringerLink 等数据库收录！ |
|
