鳜仔鱼视网膜及口腔齿的发育对摄食的适应

采用石蜡切片及HE染色的方法对鳜受精卵及1～30 d仔鱼的视网膜结构和视觉特性进行研究,结果表明:(1)受精后54 h晶状体形成,视网膜还未分化;80 h视网膜分化为外核层、内核层、内网层和神经节细胞层4层结构;98 h形成色素上皮层、视杆视锥层和神经纤维层;124 h外网层形成,视网膜10层结构发育完全。孵化后4 d开始出现少量颌齿和咽齿;5 d和14 d分别观察到腭齿和犁齿;15d时鳃耙形成但形状较小。口腔齿的数量随着仔鱼个体的生长而增加至近于成体。(2)鳜内核层分化成一层水平细胞、数层双极细胞和无长突细胞,属光感受系统不发达的类型。(3)鳜仔鱼在消化系统尚未发育完全时已经开始形成口腔齿,为提高捕食的成功率提供了基础条件,充分表现了个体发育在进化过程中与生存环境相适应的特点。(4)鳜神经节细胞层细胞随个体的生长发育而减少,孵化后29 d,体长18.36 mm时,只有一层神经节细胞,说明此时的仔鱼已适应黑暗环境生活。鳜视觉结构的变化与其从浮游到底层的生态迁移及捕食方式的变化相适应。研究亮点:从组织学研究角度对鳜仔鱼视网膜发育进行了探讨,详细研究了视网膜各组成结构的发育特征,并结合鳜仔鱼齿的发育特征,分析了其对摄食行为的适应,首次解释了伴随着视网膜发育而形成的由浮游生活到底层生活的适应,研究结果以期为鳜在种苗生产过程中正确选择开口饵料和早期动物性饵料,以降低种苗的死亡率等提供理论依据。

Histological observations of retina and teeth development and their adaption to feeding in Siniperca chuatsi

Paraffin section and HE section were adopted to examine the structure of the retina and visual characteristics of Siniperca chuatsi fertilized eggs and from newly hatched to 30 days old larvae. The main results obtained are as follows: (1)At 54 h after fertilization, lens and undifferentiated retina formed. At 80 h after hatching, the retina differentiated into four layers, including outer nuclear layer, inner nuclear layer, inner plexiform layer and ganglion cell layer. At 98 h, pigment epithelium, rods and cones layer and optic nerve fibers layer were observed. At 124 h, outer plexiform layer formed and the retina was composed of ten layers. At 4 days after hatching, a couple of jaw teeth and pharyngeal teeth appeared; At 5 days and 14 days, palatine teeth and vomer teeth appeared respectively; At 15 days, gill rakers grew but small. In one word, the quantity of the teeth increased with the growth of larvae, until nearly the same as that of the adult. (2) The structure of the inner nuclear layer of S.chuatsi has only a layer of horizontal cells, bipolar cells and amacrine cells, which shows that the retina of S.chuatsi is not sensitive to light.(3) The teeth appeared before the maturity of the digestive system in the S.chuatsi larvae, which serves to improve the success rate in catching prey. It is a full reflection of the adaptation of individual growth to the environment in its evolutionary process. (4)The quantity of the ganglion cell decreased with the development of S.chuatsi. At 29 days, the structure of the ganglion cell layer of S.chuatsi decreased to a layer of ganglion cell, which indicates that S.chuatsi larvae had adapted to the dark environment. It is revealed that the changes of visual structure of S.chuatsi are adapted to the ecological shift from pelagic to benthic habitats and to the changes of feeding methods.