THE KARYOTYPE AND BANDING-PATTERNS OF BLUE MUSSEL,MYTILUS EDULIS
WANG QIONG, TONG SHANG-LIANG (Department of Marine Biology, Ocean University of Qingdao, Qingdao 266003)
Karyotype, G- and C-banding patterns and Ag-NORs distribution feature of the chromosomes of blue mussel,Mytilus edulis, were studied. Chromosome preparation was made with 8-cell embryos,gonadal tissue of adult mussel and gill tissue of juvenile mussel. Karyotype calculated from chromosome lengths and arm ratios of ten cells was shown with: 2n=28, 12m + 10sm + 6st, NF = 50, TCL=103. 90μm, CL: 2. 735 - 4. 774μm. Chromosome Nos. 1, 2, 4, 8, 11, 12 are metacentric, Nos.6, 9, 10, 13, 14 are submetacentric, Nos, 3, 5, 7 are subtelocentric. The haploid number of 14 and diploid number of 28 confirm previous reports. But the karyotype is somewhat different from former results,which may be attributed to unproportional contraction of chromosome arms, structural rearrangement of chromosomes or differentiation of geographic subspecies, Variations of chromosome length, relative chromosome length and arm ratio were statistically analyzed and showed that variation of chromosome length among cells was conspicuous,which could be due to factors during preparation of chromosome samples. However,there was no difference among cells for relative chromosome length and arm ratio. None but one work with oyster,Crassostrea virginica, was reported before on banding- patterns in mitotic chromosomes of marine mollusc, This technique could be useful in research related to the cytogenetics and cytotaxonomy. The coincidence of distribution of Ag-NORs and positive C-banding was observed. The two pairs of NORs revealed by silver- staining were at the long arm's ends of the Nos, 3, 5 subtelocentric chromosomes, We also observed Ag-NORs polymorphisms in cells of blue mussel.