Nagasaki Prefectural Institute of Fisheries, Japan.
Comp Biochem Physiol B Biochem Mol Biol. 2011 Dec;160(4):174-80. doi: 10.1016/j.cbpb.2011.08.004. Epub 2011 Aug 25.
Cortisol, the main glucocorticoid in fish, increases during flatfish metamorphosis and peaks before the surge of thyroxine. A large body of evidence indicates the essential role of thyroxine in flatfish metamorphosis, whereas information on cortisol is limited. We administered cortisol to spotted halibut Verasper variegatus larvae in order to examine the effect on pigmentation during metamorphosis. Administration of 10 μg cortisol per mL of water from before the onset of metamorphosis (stage E) to metamorphic climax (stage G) induced the development of adult type pigment cells on the blind side of the metamorphosed juveniles and increased the occurrence of ambicolored juveniles. When 10 μg/mL cortisol was administered during stage D, stages E-F, stage G or stage H, only the administration during stages E-F induced the development of adult type pigment cells on the blind side. In addition, the expression of the gene dopachrome tautomerase (dct), a marker of melanoblasts, was enhanced at Stage E by cortisol administration. These results clearly indicated, for the first time, the enhancement of pigmentation by exogenous high-dose cortisol. Since endogenous cortisol is secreted in response to various kinds of stress in rearing conditions, these results indicate a possible influence of stress conditions in the occurrence of ambicoloration in flatfish.
皮质醇是鱼类中的主要糖皮质激素，在比目鱼变态期间会增加，并在甲状腺素激增之前达到峰值。大量证据表明甲状腺素在比目鱼变态中起着重要作用，而有关皮质醇的信息有限。我们给星斑川鲽（Verasper variegatus）幼鱼注射皮质醇，以研究其在变态过程中对色素沉着的影响。从变态开始前（E 期）到变态高峰（G 期），每毫升水给予 10μg 皮质醇，可诱导变态幼鱼的盲侧发育出成年型色素细胞，并增加双色幼鱼的出现。当在 D 期、E-F 期、G 期或 H 期给予 10μg/mL 皮质醇时，仅在 E-F 期给予皮质醇可诱导盲侧发育出成年型色素细胞。此外，皮质醇给药可增强黑素母细胞标志物 dopachrome tautomerase（dct）基因的表达。这些结果首次明确表明，外源性高剂量皮质醇可增强色素沉着。由于内源性皮质醇是在养殖条件下应对各种应激而分泌的，因此这些结果表明应激条件可能会影响比目鱼双色的发生。
