孟加拉鲥、美洲鲥和中国鲥形态学比较分析

观察、解剖107尾孟加拉鲥Tenualosa ilisha、美洲鲥Alosa sapidissima和中国鲥Tenualosa reevesii,详细记叙了孟加拉鲥外部形态和内部结构,运用传统形态学方法比较分析了3种鲥鱼的形态差异.三者形态7项可量性状比值的聚类分析结果显示,孟加拉鲥和中国鲥先聚为一类,再和美洲鲥聚为一类,这与它们的分类地位相一致.外观上,孟加拉鲥臀鳍鳍条短,被1层薄鳞覆盖;美洲鲥的纵列鳞数及体长/体高、体长/头长都大于其他2种鲥鱼.可数性状上,第一外鳃弓鳃耙和脊椎骨数目能明显区分3种鲥鱼.孟加拉鲥、中国鲥和美洲鲥的第一外鳃弓鳃耙数分别为181～219+153～224、95～131+170～175和24～31+47～55;脊椎骨数分别为46～48、37～39和55～57.在内部结构上,根据胃的形状、盲囊部的大小、幽门垂的长短和数量、肠道的弯曲数目及相对长度可以准确鉴定这3种鲥鱼.孟加拉鲥肠道最长,中国鲥次之,美洲鲥肠道最短.3种鲥鱼在消化道结构的差异,预示食性已产生分化.

Morphometrics Analysis of Tenualosa ilisha, Alosa sapidissima and Tenualosa reevesii

In this study, 107 samples of Tenualosa ilisha, Alosa sapidissima and T. reevesii were dissected and observed, and the morphological characteristics of T. ilisha were studied in detail. The morphological variations of T. ilisha and A. sapidissima and T. reevesii were analyzed using traditional morphometrics. In cluster analysis of 7 measurable parameters ratio, the T. ilisha and T. reevesii populations were clustered and then clustered with A. sapidissima. This was in confirmation with their classification status. In appearance, the short anal fin covered with squama of T. ilisha was different from that of A. sapidissima and T. reevesii. The number of columns scale, body length/body height and body length/head length of A. sapidissima were bigger than those of the other two Tenualosa species, so the A. sapidissima had a slenderer somatotype and smaller head. As for meristic characters, the first gill raker and vertebra were different from each other in these three species. The number of the first gill raker T. ilisha, T. reevesii and A. sapidissima were 181-219+153-224, 95-131+170-175 and 24-31+47-55 respectively. The number of the first gill raker T. ilisha, T. reevesii and A. sapidissima were 46-48, 37-39 and 55-57 respectively. As for internal structure, these three species could be clearly identified based on the shape of stomach, the size of blind sac, the length and the number of pyloric caecum, the bending number and relative length of intestine. At the same time, the different structures of digestive tract of the T. ilisha, A. sapidissima and T. reevesii indicated that the diets had been differentiated.