中文摘要：

文昌鱼的进化地位十分重要，对其染色体的研究在进化和比较基因组学方面有重要意义。然而文昌鱼的染色体制备困难，使研究受到了限制。本文介绍了一种改良的文昌鱼胚胎细胞染色体标本制备方法，以及用文昌鱼成体再生细胞制备染色体，首次获得了文昌鱼体细胞中期染色体标本，并观察了厦门2种文昌鱼的染色体，其中白氏文昌鱼（Branchiostoma belcheri）二倍体2n=40，日本文昌鱼（B．japonicum）二倍体2n=36。再次从细胞分类学角度证实白氏文昌鱼和日本文昌鱼作为两个独立物种的分类地位。

英文摘要：

Amphioxus has an important evolutionary position as a result of their phylogenetic position relative to vertebrates. Understanding their chromosomes would provide key points in the study of evolutionary biology and comparative genomics. The difficulty in preparing amphioxus chromosomes currently provides a significant hurdle in this research. In the current study, we describe an improved method for metaphase preparation from amphioxus embryos and methodology for preparing metaphase spreads from regenerative somatic cells. Chromosomes of two amphioxus species from Xiamen waters in China are also observed. The diploid chromosome number was found to be 40 in Branchiostoma belcheri, while B. japonicum has 36, confirming the two are distinct species from cytotaxonomic viewpoint.