Abstract
Juveniles of black seabream, Acanthopagrus schlegeli were fed with the diets containing 0, 10, 20, 50 and 100 ppm of 3,5,3'-triiodo-1-thyronine $(T_3)$ respectively to assess the effect of this hormone on skeletal development and the change of physiological conditions for 50 days. $(T_3)$ treatment lasted for initial 40 days. Fish were fed the prescribed diet by hand to satiation in $2\~4$ times per day. After an initial 40 days period, skeletal development and abnormality were examined, and after a 50 days period, food intake, hepatosomatic index (HSI), thyroid cell height (TCH) and body proximate composition were also examined. Although toed intake was not different among 0, 10 and 20 ppm, the food intake of black seabream fed with the diets containing 50 and 100 ppm of $T_3$was significantly lower than those of 10 ppm. After the initial 40 days of $T_3$ administration, $T_3$ increased the relative growth of operculum, head, caudal fin and pectoral fin to body length, resulting in severe morphological abnormalities at the highest dose. Black seabream treated with 50 and 100 ppm of $T_3$ had abnormal shapes such as lordosis and opercular curl. The HSI parameters were reversely correlation with the dietary concentration of $T_3$. After the initial 40 days of this experiment, atrophy of thyroid gland was observed in fish administered with 50 and 100 ppm of $T_3$. On the 50th day of this experiment, atrophy of thyroid gland was observed only in the group administered with 100 ppm of $T_3$, and no difference was observed on TCH among the rest fours of experimental groups. At the end of the experiment the whore body proximate analyses indicated that there were significant effects of $T_3$ level on moisture, protein, lipid and ash contents.
감성돔, A. schlegeli 치어의 골격발달 및 생리 변화에 미치는 3,5,3'-triiodo-L-thyronine $(T_3)$ 의 효과를 파악하기 위해 $T_3$를 0, 10, 20, 50 및 100ppm으로 사료에 섞어 경구 투여하였다. 실험종료시 일간섭식량은 대조구와 10ppm 및 20ppm 처리구와는 차이가 없었지만, 50ppm구 및 100ppm구는 오히려 대조구에 비해 낮아지는 것을 알 수 있었다. 체장 성장의 경우는 10ppm 처리구만이 대조구에 비해 빨랐고, 그 외 처리구는 대조구와 차이가 없었다. 체장에 대한 아가미 뚜껑, 두부, 가슴지느러미 및 꼬리지느러미 길이의 비율은 $T_3$ 처리 농도가 증가할수록 높아지는 경향이었다. 한편, $T_3$ 처리에 따른 비정상적 골격발달을 나타내는 개체는 $20\~100ppm$ 처리구에서 관찰되었으며, 50ppm과 100ppm 처리구에서 유의하게 많았다. HSI는 $T_3$ 처리 농도가 높아질수록 낮아지는 경향을 보였다. $T_3$ 처리 종료시인 사육 40일째의 TCH는 처리 농도가 높아질 수록 낮아지는 경향을 나타냈으나, 사육 50일째의 TCH는 100ppm 처리구에서만 유의하게 낮았다. 실험 종료시의 어체성분을 분석한 결과, 수분과 단백질은 10ppm 처리구에서만 대조구에 비해 유의하게 많았다. 지질은 모든 $T_3$ 처리구에서 대조구보다 적게 나타났으나, 회분은 $T_3$ 처리량이 많아질수록 높아지는 경향이었다.
(Department of Aquaculture, Pukyong National University)
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