Comparison Of Chromosomal Characteristics And Prelimenary Study On Chromosome Evolution In Sciaenidae

Sicaenids are one of the most important marine fishery groups in China.Phylogenetic relationship in this family have been studied a lot at morphological and molecular level,but still few at chromosomal level.Thus,we analyzed the karyotypic characteristics of Nibea albiflora,Protonibea diacanthus,Argyrosomus amoyensis,Sciaenops ocellatus,Collichthys lucidus and Larimichthys crocea by a variety of staining method and FISH,and combined with the previously reported data to explore the function of chromosome rearrangement on the process of evolution.The main results of this study were reported as follows:1.All karyotype of Nibea albiflora,Protonibea diacanthus,Argyrosomus amoyensis and Sciaenops ocellatus were 2n=48t.However,the karyotype of large yellow croaker is2n=2sm+4st+42t,with three pairs of bi-arm chromosomes.In spinyhead croaker,karyotypes were differentiated obviously between female and male,2n=48t(NF=48)in the females and2n=46t+1sm(NF=48)in the males,which indicated that chromosome fusion may occurred and resulted in a multi chromosome sex-determination system(X1X1X2X2/X1X2Y).2.There is only 1 pair of 18 S rDNA sites in all six sciaenids revealed by FISH with 18 S rDNA,but the distribution of 18 S rDNA sites were of 3 patterns:(1)at proximal portion of chromosome 1,chromosome 3 and chromosome 1in P.diacanthus,A.amoyensis and S.ocellatus,respectively.(2)at interstitial of chromosome 1 in N.albiflora and C.lucidus.(3)at centromeric termini of a submetacentric chromosome in L crocea.3.Highly variations were observed for the number and location of 5S rDNA in the six sciaenids.All of P.diacanthus,A.amoyensis and C.lucidu have single pair of 5S rDNA,syntenical with 18 S rDNA in C.lucidu,but non-syntenical with 18 S rDNA in P.diacanthus and A.amoyensis.Both N.albiflora and S.ocellatus have two pairs of 5S rDNA signals with different density.The strong one located on chromosome 1 syntenical with 18 S rDNA,and the weak one located on chromosome 4 in Nibea albiflora.While in S.ocellatus,all 5S rDNA sites located on the chromosomes without 18 S rDNA.L.crocea has 10 pairs of 5S rDNA signals,including 3 strong pairs 7 weak pairs.Except for one pair of weak signals located on interstitial,the other 9 pairs were locate on the whole short arm of telocentric chromosome or subtelocentric chromosome.And the signal of between arms is colinear distribution with one pair of 5S rDNA on centromeric termini.4.One pair of interstitial telomere signals were mapped adjacent to 18 S rDNA on chromosome 1 and neo-Y chromsome in spinyhead croaker,while no interstitial telomere signal was detected in the other 5 species of sciaenidae...