Study On Karyotype And Banding Patterns Of Verasper Sp.

Verasper sp. includes two species flatfish Verasper moseri and Verasper variega tus which belong to cold-temperate macrobenthos. In china,Verasper variegatus are mainly distributed in the Yellow Sea and Bohai Sea and East China Sea,but over the years for various reasons,the natural resources of Verasper variegatus are declining,the catches are extremely few,which cannot form certain catching. Verasper moseri once had the distribution records in China's Yellow Sea and Bohai Sea Area,but the fishing was not seen to attain for many years,closing to the extent of endangered. Verasper sp. with faster growth,high stress-resistance and excellent low-temperature -resistant characteristics,have become popular for their deliciousness,high values of nutrition and meat quality.At the beginning of the last century 90's Chinese started to catch the wild Vera- sper variegatus for domestication,the experiments of artificial breeding had started progressively. To the present it has been able to achieve large-scale breedings. The stu -dies to Verasper moseri began in 2004 with the introduction of seedlings from Japan,followed by experiments and developments of aquaculture. The breeding of Verasper moseri have reached large-scales now. Verasper sp. belong to valuable marine fish which have broad market prospects.In this paper,the chromosomal conventional karyotypes and banding patterns on Verasper sp. were studied. The author has made the preliminary discussion to their kar yotypes and the evolved relations,compared the relationship between the two speci- es,which could provide the reference for reasonable use and protect of their fishery resources,and the genetic background information and scientific basis for the flound- er fish's crossbreeding and culturing. It also has the important meanings for marine fi- shes diversity protection.1. The karyotype of Verasper sp. was studied through the chromosome preparation obtained from head kidney by the method of injecting PHA and colchicines. After low permeating and Carnoy′s fixation,air drying method was used to make chromosome samples,which were dyed by Giemsa afterwards. The results showed that the diploid chromosomal number of V. moseri and V. variegatus is 2n=46 and their respective kar- yotype formulae are 2n=2sm+44t,NF=48 and 2n=46t,NF=46. It means that there are1 pair of submetacentric chromosomes and 22 pairs of telocentric chromosomes in V. moseri and 23 pairs of telocentric chromosomes in V. variegatus. There are no visible evidence of polyploidy chromosome and sex chromosome. According to the karyotyp e of the 2 species,Verasper sp. belong to height classification in system classify and they are the more primitive groups. V. moseri may be more evolutional than V. variega tus.2. Using the methods of Sumner (1972) slightly modified,V. moseri shows more complicated C-bands. There are 4 pairs of chromosomes which have the whole chromosomes C-bands,their number is 3,13,20,22;the number of 1,4 and 8 chromosomes have interstitial C-bands;the No.9 chromosome don't have C-bands,and the rest of the chromosomes have the centromere C-bands. The heterochromatin content of V. moseri is 54.91%. C-bands of V. variegates are located mainly in the centromere regions of chromosomes except the No.19 and 22 chromosomes,the No.19 chromosome of V. variegates have terminal C-bands and the No.22 chromosome of V. variegates have the whole chromosomes C-bands. The heterochromatin content of V. variegates is 30% which less than V. moseri. The characteristics of the number and sites of C-bands in Verasper sp. chromosomes reveal that V. moseri is more evolutional than V. variegates which is consistent to their karyotype.3. The chromosomes of Verasper sp. were thus stained according to the method of Howell (1980) that was slightly modified. The study showed that 2 Ag-NORs bands were observed in these 2 species in their metaphases respectively. The position of nucleolus organizer regions of V. moseri was situated on the terminal region of short arm of the submetacentric chromosomes. The position of nucleolus organizer regions of V. variegates was situated on the terminal region of No.2 chromosomes. This may explain that No.2 chromosomes of V. moseri and V. variegates are highly homologous because the submetacentric chromosomes of V. moseri also belong to No.2 chromosomes according to the relative length of it's chromosomes. It shows that the 2 species of the Verasper sp. have very close relationship. One pair of telomeric NORs reveal that Verasper sp. are the more primitive groups.4. The G-banding was carried out by the trypsin method. The study showed that V. moseri and V. variegates have more difference in G-bands of chromosomes,but they have the same total numbers of G-bands which are 59. V. moseri have 37 deeply stained bands and 22 shallow stained bands,while V. variegates have 38 deeply stained bands and 21 shallow stained bands,but the region of G-bands in Verasper sp. chromosomes are different. G-banding is susceptible to interference by variations such as the degree of chromosome contraction,so the results in this paper are not satisfactory. It also may be due to the larger number and the tiny shape of fish chromosome and their DNA composition of chromosomes.5. Calculated the karyotype resemblance near coefficients (λ) and the distance of karyotype evolution ( De ) of Verasper sp.,the resultλ=0.98, De =0.02 indicate that the difference between V. moseri and V. variegates are very little,they have very close relationship.