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KMID : 0894520010050010039
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Development & Reproduction
2001 Volume.5 No. 1 p.39 ~ p.45
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Differentiation of Thyroid Gland and Changes of Thyroid Hormone Concentration during Early Development of Black Rockfish , Sebastes schlegeli
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강덕영
장영진/정의영
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Abstract
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Black rockfish Sebastes schlegeli is one of scopaenid fish giving birth to yolk-sac larvae and distributed around the coast of Korea and Japan, and is one of main species which is cultured in Korea. The difffrentiation of thyroid gland and the changes of thyroid hormones (THs) concentrations in the whole body during early development of this species were examined and the relationship between thyroid gland and their growth will be presented. Total length (TL) and body weight (BW) of the larva at the parturition were 6.3±0.1 mm and 3.6±0.1 mg, respectively. The larvae transformed to juvenile after 30th day after parturition. According to Hoshiai(1977), they had gown into stage Fl (TL 13.2±0.9 mm, BW 46.5±1.5 mg) at 50th day. The thyroid gland of black rockfish was first observed histologically in hatching larvae in mother fish. The larvae just after parturition have 1∼3 of the thyroid follicles diffrentiated between basibranchial bone and ventral aorta, at the base of the first gill arch. In this time, thyroid follic1e number (TFN),thyroid follicle diameter (TFD) and thyroid cell height (TCH) were 1.6±0.8 pieces/inds., 18.1±0.6 μm and 4.1±0.2 μm, respectively. TFN and TFD at 50th day were increased to 32.5±6.9 pieces/inds. and 41.5±1.7 μm, respectively. These results indicate that they are related to the growth of black rockfish during early development. However, TCH indicates that the activity of thyroid gland appearedat special day, eg. 5, 20 and 50th day, suggesting that TCH may have some role in the physiological activity. L-thyroxine (T4)concentration decreased sharply to 10 days after parturition, and at 25th day (metamorphosis stage) increased markedly to 3.44±0.93ng/g fish. After this time, T4 concentration decreased at 35th day, but then increasedagain to the highest concentration, 5.63±0.70ng/g fish. 3,5,3'-triiodo-L-thyronine (T3) concentration declined sharply from just after pafurition (4.96±1.90 ng/g fish) to 5th day (0.30±0.07 ng/g fish). However T3 concentration increased markedly to 0.95±0.11 ng/g fish at 30th day and then did not significantly change until 45th day, increased also sharply to 1.67±0.23 ng/g fish at 50th day.
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KEYWORD
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