Growth and Activities of Larvae Born from the Triiodothyronine-Injected Parturient Rockfish, Sebastes schlegeli

We have experimentally evaluated the content of thyroid hormones (THs), the growth and activity of larval rockfish (Sebastes schiegeli) born from parturient mother fish injected with 20 $\mu$g/g BW of 3,5,3-triiodo-L-thyronine ($T_{3}$). There was no difference of L-thyroxine ($T_{4}$) levels between controls (sham control and control) and $T_{3}$ groups in yolk-sac larvae just born from broodstock, while $T_{3}$level of $T_{3}$ group was significantly increased compared with controls. In addition, the both larval $T_{3}$ and $T_{4}$ levels in $T_{3}$ group were always higher than those of control during experimental period. Also, there were significant differences in the development of larvae from the two groups. The larval growth in total length and body weight according to the elapsed days after parturition showed the linear and curve equations, respectively, and the slopes of $T_{3}$ group were significantly higher than those of control. The survival rate of larvae in $T_{3}$ group was higher than that of control. Although the survival rate in $T_{3}$ group under the condition of starvation was significantly depressed compared with the control, larval swimming index in $T_{3}$ group was higher than control. Finally, these findings suggest that the exogenous $T_{3}$ could be transferred into hatched larvae in parturient rockfish by maternal injection, and subsequently the exogenous hormone could play some roles on physiological metabolism of larvae after parturition and may confer a distinct advantage to the fragile larvae during the early developmental stage.

출산기 모체에게 triiodothyronine (T3) 주사하여 얻은 조피볼락, Sebastes schlegeli 자어의 성장 및 활성

출산기에 임박한 조피볼락 암컷에 20mg/kg체중의 농도로 3,5, 3'-triiodo-L-thyronine $(T_{3}$)를 주사한 뒤, 출산 자어로의 호르몬 전이여부, 자어 성장과 활력을 조사하였다. 출산자어의 갑상선 호르몬을 분석한 결과,출산직후에 $T_{3}$구가 대조구 보다 높은 $T_{3}$농도를 나타냈으나, L-thyroxine $(T_{4}$)의 농도는 대조구와 유의차가 없었다. 그러나 실험기간 동안 어체내 모든 실험구의 감상선호르몬 농도는 $T_{3}$가 $T_{4}$에 비해 상대적으로 낮았고, 실험구별로는 $T_{3}$구가 대조구에 비해 높은 것을 알 수 있었다. 자어의 성장률은 대조구에 비하여 T,구에서 높았으며, 출산후 경과일수에 따라 직선적인 전장성장 경향을 나타냈다. 실험종료시 생존율은$ T_{3}$구의 자어가 대조구에 비해 높았으며, 유영활성에서도 $T_{3}$구의 자어가 대조구에 비해 유의하게 높았다. 출산직전 $T_{3}$ 모체주사는 외부영양원 섭취개시기의 자어성장 및 생리활성을 증진시키는 데 효과적인 것으로 나타났다. 이상의 연구결과로부터 출산전 모체주사를 통하여 외인성 $T_{3}$가 자어로 전이되며, 전이된 호르몬은 출산후의 자어의 초기 발달기 동안 생리적으로 긍정적인 작용을 할 것으로 추측된다.