泥蚶(Tegillarca granosa)不同地理居群同工酶变异及遗传分化的研究

STUDY ON GENETIC VARIATION BY ISOZYME IN DIFFERENT POPULATIONS OF BLOODY CLAM TEGILLARCA GRANOSA

采用聚丙烯酰胺凝胶同工酶电泳技术对韩国釜山、山东荣成、浙江奉化和乐清、福建福鼎、广东汕头和湛江7个地理群体的泥蚶进行同工酶分析,结果发现在所检测的MDH、ADH、ATPase、LDH、POD、IDH、SOD、SDH、ME、SCD和EST等11种同工酶中,除ATPase外其他10种在各地理群体之间存在着或大或小的差异,特别是汕头和湛江两地理群体与其他5个地理群体之间的这种差异尤其显著,两组间的平均酶距达0.4209,而汕头和湛江群体间的差异较小,两者酶距为0.0909;釜山、荣成、奉化、乐清、福鼎5个群体间的平均酶距也只有0.0191。这说明上述7个地理群体泥蚶已明显分化为两大类群,汕头和湛江群体为一类群,其他5个群体为一类群,两大类群的分界线在东海和南海的分界处。还对不同泥蚶群体间的同工酶分子标记的建立、不同群体间的遗传变异水平及泥蚶群体间分化的可能机制等问题进行了探讨,以期为泥蚶资源的进一步开发和利用提供科学资料。

Bloody clam Tegillarca granosa (Linnaeus), distributing along south and west Pacific ocean, belonging to Mollusca, Bivalvia, Arcoida, Arcidae, is one of four traditional farming species of shellfish in China. It plays an important role in the country's marine economy, especially in south China. Nowadays, its intra-species differentiation between south and north of Fujian Province has puzzled many researchers. The differentiation is shown as follows: the south populations have flatter shell, lighter shell color, and less blood than the north ones. The time of their sexual maturity and taxonomic status between the two population are also very different. Some believed that they might be divided as two different species. Because of their high quality protein and good tastes, they are currently cultured in large scale in maritime China. But in recent years increasing production and worsening ocean environment resulted in great suffering from losing natural resources and genetic diversities. So, in order to develop the farming and artificial breeding technology, one must probe into the present state of genetic variation in currently-existed populations, which would help make efficient measures to protect the genetic resources. Sample of 7 different populations of T. granosa used in the genetic variation study were collected from Pushan of Korea, Shantou, Zhanjiang, Fuding, Yueqing, Fenghua, Rongcheng of China. In laboratory, the samples were homogenized in 0.05% mercaptoethanol buffer at ratio of 1 ∶ 3 (W/V) with ice-bath immediately and centrifuged by 12000r/min for 30minutes at 4℃. The supernatant was collected and used in the rest steps of experiment. The genetic variation of T. granosa was investigated in 7 populations using vertical polyacrylamide gel electrophoresis (PAGE). Each enzyme band number of each population was recorded and the isozyme similarity and distance was calculated and presented using method by Aquado and Avise (1981). The study showed that 10 of the 11 isozymes checked had showed certain variation between populations. Two groups were recognized clearly. One consisted of Shantou, Zhanjiang populations and another made up of other five populations, and the isozyme distance between the two is 0.4209 while inter-group distances are much smaller. It may suggest that the 7 populations of T. granosa along Chinese coasts have developed into at least two groups separated by a geographical boundary between the East and the South China Sea. Hereditary relationship and clustering analysis were also conducted using UPGMA method. It showed that the degree of genetic variation between populations is closely related to the latitude of the animal living with certain ocean conditions. In this paper, the authors discussed the questions such as the possibility of isozyme molecular marking of each geographical population, the degree of genetic variation among populations and the probable mechanism of environmental affect on the species evolution. Suggestion is made on providing more materials for further development and exploring better utilization of this animal.