条石鲷早期发育阶段体表色素的变化和色素带的形成

Studies on body pigment variation and band formation during early development stages in Oplegnathus fasciatus

为了解条石鲷早期发育过程重要形态特征的变化,在广东饶平通过全人工繁殖和池塘育苗,观察了条石鲷胚胎和仔稚幼鱼发育过程体表色素的变化和色素带的发生和形成过程,统计了每个发育阶段不同色素带的出现频率。结果显示,条石鲷的色素细胞有黑色素、黄色素和褐色素3种,均为菊花状色素,其色素的发生和变化从胚体期开始贯穿了整个早期发育阶段。随着仔、稚鱼发育,色素细胞由小变大,分枝从较短、较少到较长、连成网状再到分枝更密、更短,细胞由稀疏、均匀分布到成丛密集分布,鱼体颜色也由浅且透明变得很深。将条石鲷体表色素带的形成过程分为8个阶段,分别对应于无色素带和7条色素带的形成;色素带最初是从头顶和腹部下方对应于前3条色素带的3个菊花状色素的出现开始的,12~16 d是色素带痕迹基础的形成期;在水温22~27℃条件下,从17 d形成第1条色素带开始,至32 d形成7条色素带;不同阶段色素带的出现频率不同;色素带的形成时序为第3条→第4条→第2条→第1条→第5条→第6条→第7条。研究表明,色素带的形成是条石鲷仔、稚、幼鱼变态的重要特征,所有色素带的形成都是从1个或几个色素细胞的发生开始的。

Body pigment and band are important morphological characteristics of fishes. Pigment variation and band formation during early development are extremely important metamorphic traits, marking the qualitative changes from one stage to another in early development of fish. The formation and changes of fish body color is the result of adaptation to environmental change. It is the important embodiment of environmental change and health, along with the environment, age, health status and physiological changes, fish body color changes accordingly. For understanding the changes of important morphological characteristics during early life stages of Oplegnathus fasciatus, complete artificial propagation and seedling pond rearing were carried out in Raoping, Guangdong Province. Body surface pigment variation and band formation during embryo, larva, juvenile and young of O. fasciatus were observed, and the frequency of bands formation at different life stages was calculated. Results showed that three kinds of pigment cells were found in a chrysanthemum shape,including melanophore,xanthophore and brown pigment. Pigment could be observed in embryonic stages, their appearance and transformation run throughout the early development stages. Pigment cells in embryo and newly hatched larva were small in size, branches short and few, with rare and even distribution, leading light and transparent in body color. With the development of larva, pigment cells increased in size, longer in branches, and some of them connected in net-shape. In late larva stage, especially in band formation period, chrysanthemum shape pigment cells were found to be more, denser and shorter in branches, distributed densely, resulting in deep color on the body. The pigment band development was divided into 8 stages,corresponding to that of non-pigmented band and formation of 7 pigment bands, respectively. Pigment bands appeared first on the head and abdomen at the same time, corresponding to the 3 chrysanthemum shape pigment on anterior 3 pigment bands. The period from 12d to 16d was the formation stage with pigmented cell accumulation. At the water temperature ranging from 22 to 27 ~C, first band could be found at 17d after hatching, and 7 bands all formed up to 32 d after hatching. Formation of 7 pigment bands was developed in sequence：3rd band--→4th band-→2nd band --→lst band-→5th band--→6th band--→7th band. Adult fish colored in black from rostrum to eye, black or brown in margin of caudal fin, changeable in body color, white in body in general, becoming yellow-brown when stressed. In conclusion, formation of bands is the important metamorphic trait in larva,juvenile and young of O. fasciatus. Occurrence and sequence of pigment bands vary with the species. Generally, formation of all bands originated from occurrence of one or several pigment cells.