温度对马来西亚红罗非鱼越冬期体色的影响

Effects of temperature on body color of Malaysian red tilapia during overwintering period

为了解马来西亚红罗非鱼体色分化变异的遗传分子机制,以期解决其越冬期的体色变异问题,本研究比较了越冬期不同温度处理(16、20、25和30°C)对其表观体色、酪氨酸酶活性以及皮肤色素带和黑色素细胞的影响。实验50 d后发现,16°C组大部分鱼体较实验开始时变黑,整个鱼体呈现青灰色,20°C组多数鱼体腹部也变为青灰色。随着温度的升高,红罗非鱼背部皮肤、腹部皮肤和血清中酪氨酸酶的活性逐渐升高,25°C时达到最高值,而随着温度的继续升高,30°C组鱼的酪氨酸酶活性反而降低。血液中tyr m RNA的表达量随着温度的升高而升高,25和30°C组红罗非鱼肌肉中的tyr m RNA表达量也显著高于16和20°C组。切片显微结构发现,随着温度的升高,红罗非鱼背部皮肤的黑色素细胞数量减少。研究表明,马来西亚红罗非鱼越冬期的体色变异可能是其皮肤黑色素细胞数量和体内酪氨酸酶活性改变的结果,深入研究其调控机制有助于了解鱼类体色遗传机理并进行体色性状的改良。

In recent years, red tilapia has been gaining popularity due to its very fast growth, the absence of black peritoneum, salinity tolerance and adaptability to any culture system. However, the pigmentation differentiation in genetic breeding and skin color variation during the overwintering period are the main problems limiting the development of commercial red tilapia culture. The pigmentation differentiation is not reversible and skin color variation during overwintering period is reversible with the environmental temperature increasing. Coloration patterns including whole pink, pink with scattered black spots and pink with scattered red spots have been found in our breeding population. In order to further understand the genetic molecular mechanism of pigmentation differentiation and variation so as to solve the skin color variation during overwintering period, this research compared the effects of different temperatures（16, 20, 25 and 30 °C） on apparent color, tyrosinase（Tyr） activity and skin pigment cells of Malaysian red tilapia during overwintering period. After fifty days experiment, we found the body color of most fish in T16 group changed to pewter from pink at the beginning. Most of the abdominal skin color in T20 group fish also varied to pewter. But the fish body color in T25 group had only slight change and the body color of T30 group was still whole pink. The Tyr activity of fish back skin, abdominal skin and serum increased with increasing of temperature, and was the highest in 25 °C group fish. However, the Tyr activity decreased in 30°C group fish. The blood tyr m RNA expression increased with increasing of temperature, and the muscle tyr m RNA expression in 25 and 30 °C group fish were higher than that in 16 and 20 °C group. The melanocytes of fish dorsal skin decreased in number with increasing of temperature by slice microstructure observation. The results suggest that the color variation during overwintering period of red tilapia may be related to the changes of skin melanocytes and Tyr activity. The further study of the regulatory mechanism would help to understand the genetic mechanism of fish body color and improve the body color features.