GH-transgenic coho salmon (Oncorhynchus kitsutch) juveniles in tGH＊Tand tGH*PTU were fed with the diets containing 1 ug/g fish of 3,5,3'-triiodo-L-thyronine (T) and 30 ug/g fish of 6-n-propyl-2- thiouracil (PTU), respectively, to assess the effect of these drugs on the change of physiological activity, growth and survival rate in comparison with normal transgenic (tGH＊C) and nontransgenic coho salmon (Wild) for 90 days. Although the daily food intakes of all transgenic (tGH)-groups were higher than Wild, the amount was reduced by exogenous PTU supply. The fred efficiencies of tGH-groups were lower than Wild, but the efficiency was reduced both by Tand PTU. The survival rate of tGH-group was significantly higher than that of Wild, but there was no significant difference among tGH-groups. Although the growth of tGH-coho salmon was faster than Wild. the growth rate of transgenic salmon was increased by exogenous T, but was reduced by PTU Plasma TTlevels of tGH-groups was approximately 2-fold higher relative to Wild, but there were no difference of plasma TTlevels among tGH-groups. plasma TTlevel or tGH-coho salmon was increased by exogenous Tadministration, but was reduced by exogenous PTU. In addition, although plasma GH levels of all tGH-groups were higher than that of Wild, the GH level in plasma of transgenic coho salmon was increased by exogenous Tand reduced by exogenous PTU. In the meantime, the transgenic fishes also displayed head, jaw and opercular abnormalities typical of the offsets of this gene construct in coho salmon, indicating that some imbalance in growth processes has been induced. However, the abnormalities of transgenic coho salmon was reduced following exogenous PTU administration.

In Pleuronectiformes, blind-side malpigmentation (hypermelanosis) is common in cultured flatfishes, and is economically important. To understand the mechanism of blind-side hypermelanosis in flatfishes, we examined when the malpigmentation initially occurred, and studied how the symptoms proceeded during early development of the starry flounder, Platichthys stellatus. To assess quantitative pattern changes of blind-side skin, we observed morphological development of the whole body from 22 (total length [TL] 10.0±0.2 mm and body weight [BW] 8.8±0.57 mg) to 110 days (TL 23.4±0.7 mm, BW 193.6±23.3 mg) after hatching (DAH), and also examined the malpigmented area rate of blind-side skin and the malpigmented fish ratios. The experimental animals were reared in fiberglass-reinforced plastic (FRP) tanks in water at a temperature of 18.9±1.9℃ and salinity of 32.6±0.6 psu and were fed with rotifer and Artemia nauplii from 22 to 48 DAH, and with A. nauplii and commercial feed from 49 to 110 DAH. As results, the first staining patch seen by the naked eye was observed around the area between the anus and pelvic fin or caudal edge of the trunk at 80 DAH (TL 20.6±0.5 mm, BW 112.5±8.8 mg). The pigmented area and the pigmented fish ratios were significantly increased from 80 to 110 DAH. These results indicated that malpigmentation on the blind side of starry flounder was initially observed at about 2 cm in length and 100 mg in weight, and the pigmented domain on the blind-side skin was continually broadened by the differentiation of pigmented cells (melanophores and xanthophores) with growth.