美洲鲥的形态特征与细胞核型

Morphological characteristics and karyotype of American shad Alosa sapidissima

通过观察、解剖美洲鲥Alosa sapidissima,详细描述了其外部形态和内部结构,并对其核型进行了研究分析。结果表明：美洲鲥体呈纺锤形,鱼体背部为灰黑色,略带蓝绿色光泽;口端位略偏上口位,脂眼睑发达,鳞片较大,侧线不发达,鳃耙细长而致密,第1外鳃弓鳃耙数为24-31＋47-55;鳍式分别为D.3-13-16,P.1-16-17,V.1-8,A.1-2-17-19,C.23;体长分别是体高、头长、尾柄长、肠长和肛前体长的3.48倍、4.19倍、6.88倍、2.12倍和1.44倍,头长分别是吻长、眼径和眼间距的3.60倍、5.13倍和3.99倍,体高是体宽的2.27倍,尾柄长是尾柄高的1.71倍;胃发达呈＂Y＂型,幽门盲囊长且细,有92-115条;鳔2室,与体腔等长;体长（L）与体质量（W）的幂指数关系为W=0.0096L3.1429（n=47,R2=0.9753）,肥满度系数为1.53;染色体数目2n=48,核型公式为4 sm＋44 t,NF=52。

The morphological and structural characteristics and karyotypes were observed in forty-seven samples of American shad Alosa sapidissim by anatomy.The fish has a moderately fusiform body,and is silvery in color with blue or blue-green metallic luster on back.The fish has point mouth with lower jaws,well developed eyelids,large cycloid scales,and lateral line poorly developed with 56-62 scales.Gill rakers are long and slender with 24-31＋47-55 gill rakes on the first arch.The soft fin rays are found to be as： D,3―13-16;V,1―8;P,1―16-17;A,1-2―17-19;C,distinctly forked,23.The measurable morphological parameters of the fish are also described.The Y-shaped stomach is well developed with slender pyloric caeca of 92-115.The swim bladder consists of one anterior chamber and one posterior chamber.The relationship between body length（L） and body weight（W） was expressed as W=0.0096L3.1429（n=47,R2=0.9753） and the condition factor was 1.53.The diploid fish has chromosome number of 2n=48 and the karyotype is found 4sm＋44t,NF=52,and no strange size chromosomes related to the sex was observed.