洞庭湖流域沅江蚬属贝类的倍性研究

Ploidy Investigation of Corbicula from the Yuan River,Lake Dongting Basin

洞庭湖流域蚬属(Corbicula)贝类资源丰富,但其倍性尚未见报道。流式细胞术是一种基于DNA含量的动物倍性鉴定方法,目前尚未见其应用于蚬的倍性鉴定。本研究在传统核型分析的基础上,采用流式细胞术对沅江常德鼎城区江段的蚬进行倍性鉴定,梳理倍性与其形态、性别间的关系,以期为蚬的种质资源评价和管理提供理论依据。结果显示:45个样品中有二倍体30个,三倍体15个,核型公式分别为2n=36=2M+2SM+32ST和3n=54=3M+15SM+36ST。分别以二倍体太平洋牡蛎(Crassostrea gigas)和泥鳅(Misgurnus anguillicaudatus)为参照,测得两种倍性蚬的DNA含量比值均为2∶3。30个二倍体中雌雄同体、雄性和雌性的占比分别为53.4%、23.3%、23.3%;15个三倍体中雌雄同体、雄性和雌性的占比分别为46.7%、40.0%、13.3%。方差分析发现,两种倍性蚬的壳长、壳宽和壳高并无显著差异,但二倍体蚬的壳宽与壳长的比值显著大于三倍体蚬(P<0.05)。结果表明:流式细胞术简化了蚬的倍性鉴定,证实了核型分析结果,即二倍体和三倍体蚬共存于沅江常德鼎城区江段,且该江段两种倍性蚬均以雌雄同体为主,雌雄异体共存。开展大尺度环境因素对蚬倍性和性别特征的影响研究,有助于全面解析蚬属贝类倍性和生殖特征的演化机制。

The clams of the genus Corbicula are the dominant shellfish in Lake Dongting Basin,but their ploidy has not been investigated yet.Flow cytometry,as an efficient method for ploidy identification based on DNA content,has not been applied to Corbicula.In this study,besides the traditional karyotype analysis,flow cytometry was also used to identify the ploidy of Corbicula clams in Yuan River of Lake Dongting Basin.The relationship of the ploidy with clam morphology and gonad was further analyzed to provide a theoretical basis for the evaluation and management of Corbicula germplasm resources.The results showed that there were 30 diploids and 15 triploids in 45 collected samples,and their karyotype formulas were 2n=36=2M+2SM+32ST and 3n=54=3M+15SM+36ST,respectively.Using diploid Crassostrea gigas and diploid Misgurnus anguillicaudatus as references,the DNA content ratios of these clams with two different ploidies were measured to be 2︰3.Among the 30 diploids,the proportions of hermaphrodite,male and female were 53.4%,23.3%and 23.3%,respectively.The proportions of hermaphrodite,male and female in the 15 triploids were 46.7%,40.0%and 13.3%,respectively.One-way ANCOVA,with shell weight as the covariate,showed that there was no significant difference in shell length,width and height between the two ploidies,but the ratio of shell width to length of diploid Corbicula was significantly greater than that of triploid(P<0.05).The above results indicated that compared with the karyotype analysis,flow cytometry was a more simplified method to identify Corbicula polyploidy.Co-existence of diploid and triploid as well as hermaphrodite and dioecism in Yuan River was confirmed using this method.The study on the effects of large-scale environmental factors on ploidy and gonadal characteristics of Corbicula is helpful to comprehensively understand mechanisms of ploidy and reproductive evolution of Corbicula clams.