NUCLEOLAR ORGANIZER REGION VARIATION IN THE CHROMOSOMES OF 3 OYSTER SPECIES

C Thiriotquievreux (1) , A Insua

1 Station Zoologique de Villefranche

Patterns of nucleolar organiser region (NOR) variation were studied in the oysters (Bivalvia: Ostreidae) Crassostrea gigas (Thunberg) and Ostrea edulis L. Comparison of the pattern of NORs within and between C. gigas, O. edulis and Ostrea denselamellosa Lischke (data after Insua & Thiriot-Quievreux, 1991) indicates that: (i) the chromosomal locations of the Ag-NORs were terminal on metacentrics for C. gigas and O. denselamellosa but on the long arms of submetacentrics for O. edulis; (II) the position of NORs within karyotypes showed a specific pattern: pair 10 for C. gigas, pairs 9 and 10 for O. edulis, and pairs 3 and 8 for O. denselamellosa. Thus, interspecies heteromorphisms detected in this study included the number of Ag-stained NORs per genome, their chromosomal location and their position within karyotypes, Intraspecific variations or heteromorphisms were also detected within the three species investigated but at different degrees. C. gigas displayed a consistent number of homologous NOR chromosomes but a heteromorphism for NOR size. O. edulis and O. denselamellosa were characterized by a strong heteromorphism involving the apparent number of NOR sites per cell.

Domaines: Océanographie

C Thiriotquievreux, A Insua. NUCLEOLAR ORGANIZER REGION VARIATION IN THE CHROMOSOMES OF 3 OYSTER SPECIES. Journal of Experimental Marine Biology and Ecology, 1992, 157 (1), pp.33-40. ⟨10.1016/0022-0981(92)90072-I⟩. ⟨hal-03476520⟩