본 연구는 넙치를 인공사육 시설에서 육성할 때 나타나는 무안측 흑화(착색증)의 스트레스 관련 성을 확인하기 위해, 무안측에 체색이 없는 것(정상 그룹)와 체색이 있는 것(흑화 그룹)들 사이 스트레스 인자 비교 실험을 실시하였다. 본 실험에 사용된 실험어는 평균 전장 21.5±0.42 cm, 평균 무게 87.5±6.1 g였으며, 실험어의 무안측 착색면적률은 정상 그룹 0.63±0.12%, 착색증 그룹 16.7±4.7%였다. 분석한 스트레스 관련 인자는 혈중 GLU 및 TP, 코티졸 및 갑상선호르몬(FT3 & FT4) 농도 및 어체 성분(수분, 조단백, 조지방, 조회분)이었다. 실험 결과, 정상과 무안측 착색 넙 치에 있어 혈중 GLU 및 TP의 농도는 정상 형질보다 착색증 형질에서 유의하게 높게 나타났다. 혈 중 호르몬 농도에 있어 갑상선호르몬의 경우 정상과 착색증 그룹 사이에는 유의차를 찾아볼 수 없지만, 코티졸은 착색증 그룹이 정상 그룹에 비해 유의하게 높게 나타났다. 어체 중 영양 성분의 경우, 수분과 회분은 그룹 간 유의차가 없었지만, 조단백은 착색증 그룹이 정상보다 다소 낮으며, 조지방은 정상보다 유의하게 높았다. 이상의 스트레스 인자를 통한 정상과 착색증 그룹 간 비교 를 통해 알 수 있듯, 양식산 넙치의 착색증은 만성적이 약한 스트레스에 관련되어 있을 가능성이 높은 것으로 확인되었다.

To investigate the involvement of prepro-proopiomelanocortins (POMCs) with hypermelanosi on the blind side of olive flounder, Paralichthys olivaceus, we surveyed tissue sites in which the three POMCs genes are expressed, and compared pituitary-ofPOMCs (ofPOMC-Ⅰ, Ⅱ and Ⅲ) mRNA activities between the normal and the hypermelano flounders. For the studies, we refereed to the information of ofPOMC-Ⅰ and Ⅱ genes in NCBI, but we try to newly discover ofPOMC-Ⅲ sequence. At first, we cloned and characterized cDNA encoding its ofPOMC-Ⅲ from the pituitary of olive flounder The ofPOMC-Ⅲ cDNA consists of 1,258 bp nucleotides and 7 peptides (Signal peptide, N-POMC, α-MSH, CLIP, N-β-LPH, β-MSH and β-END-like peptide) encoded in 231 amino acids. In the test of tissue distribution of ofPOMCs in olive flounder, we found that ofPOMC-Ⅰ is expressed in pitutary only, but ofPOMC-Ⅱ and Ⅲ are expressed in all tissues examined. In the comparison of ofPOMCs mRNA expression between the normal and the hypermelano fish, expression of ofPOMC-Ⅰ, Ⅱ mRNA was significantly higher in the hypermelano group than in normal group, but ofPOMC-Ⅲ was not significantly different between two groups.

In the present study, to understand the process of abnormal pigmentation (hypermelanosis) on the blind side of olive flounder P. olivaceus during early development, we investigated an time that staining on the blind side is initially observed with the naked eyes, counted the number of stained spot on the blind, and calculated the ratio of area stained on the blind side, and the ratio of fish pigmented on the blind side with growth. The present experiment was initiated at 24-day after hatching (dah), just after the starting of metamorphosis, in which fish mean size is total length (TL) 12.4±0.2 ㎜ and body weight (BW) 19.9±0.7 ㎎, and was finalized at 94-dah (TL 72.0±0.6 ㎜, BW 3,912.3±119.4 ㎎). The experimental animals were reared in FRP tank at 20±0.5℃ in water temperature and 30.9±0.1 psu. The experimental animals were feed with rotifer, Artemia nauplii and commercial food according growth stage. As results, the pigmented spots are composed with adult-type melanophores. The first spot was found in microscopy level at 38-dah (TL 18.3±0.4 ㎜, BW 57.6±4.1 ㎎), but the first staining spot observed with the naked eye was found 52-dah (TL 37.6±0.5 ㎜, BW 534.2±30.9 ㎎) around the pectoral fin and the caudal peduncle. The pigmented spots became more distinctive and expanded around the edge of rear on the blind side. The number of spots and the ratio of area stained on the blind side sharply increased between 31-dah and 80-dah, and between 66-dah and 94-dah, respectively. The ratio of fishes stained on the blind side increased between 45-dah and 73-dah, and then was stagnated to 94-dah. Therefore, these results concluded that the pigmentation on the blind side of olive flounder is not an temporary and reversible color change but an irreversible abnormal phenomenon that pigment cells is continuously differentiated on the blind side with growth for early development just after metamorphosis in artificial culture conditions.