Studies On The Karyotype And Ag-NORs Of Wild And Cultured Chinese Black Sleeper Bostrichthys Sinensis

In this paper,the karyotype and banding pattern of both wild and cultured Chinese Black Sleepers(Bostrichthys sinensis) were studied using the methods of Giemsa-staining and Ag-NORs techniques.The wild Chinese Black Sleepers were obtained from the west coast of Beibu Bay,Jiulong River estuary and Funing bay.The cultured Chinese Black Sleepers were caught from Dongshan Island.The main results and conclusions are as follows:The three wild populations and one cultured population samples presented uniform diploid numbers(2n=46) and the same karyotypic formulae:2n=46,46t, NF=46.Not characteristic features,such as secondary constriction,satellites or sex chromosomes were observed in all samples including wild and cultured populations.Polymorphisms were found in the division phases Ag-NORs in Chinese Black Sleeper of different populations and different sexes,including the sizes,numbers and positions.The Ag-NORs located in homologous chromosomes or between homologous chromosomes could be the same or different in sizes.There were no significant differences in the Ag-NORs number of division phases between each two populations(P＞0.05),but there existed some differences in the maximum number of Ag-NORs between different populations and sexes.Four kind of division phases of Ag-NORs could be classificated according to their phenotypes:Ⅰ.one pair of Ag-NORs existed in the terminal of one pair of chromosomes,which could be in the biggest ones or the bigger ones or the smaller ones;Ⅱ.one pair of Ag-NORs existed in the centromere of one pair of the biggest chromosomes or the bigger chromosomes;Ⅲ.two pair of Ag-NORs existed in the terminal of two pair of chromosomes,the Ag-NORs could be on the biggest pair and the bigger pair,the biggest pair and the smaller pair,and the bigger pair and the smaller pair;Ⅳ.two pair of Ag-NORs existed in the centromere of the biggest pair and a smaller pair of chromosomes.A special phenotype of division phases Ag-NORs was observed in cultured hermaphrodite,which is distributed in whole arm of a smaller chromosome.This special whole arm Ag-NORs was reported first in the present study. The maximum number of nucleolus in interphase nucleus of both wild and cultured Chinese Black Sleeper was 4,most of the interphase nucleuses had 2 nucleoli. The mean difference of NORs numbers existed between each two populations,but the mean numbers of of nucleolus were almost the same between different sexes in a population.