Supernumerary chromosomes in Nephrops norvegicus L (Crustacea, Decapoda)

Supernumerary chromosomes have been identified in the chromosome complement of Nephrops norvegicus L. by C-banding and restriction endonuclease-induced banding. These chromosomes showed peculiar features of typical B chromosomes in terms of heterochromatin content, asynapsis and distorted segregation. The presence of these chromosomes can, at least partially, account for the numerical variability already observed in this species; 2n and n values determined by counting these chromosomes separately gave a less variable number of chromosomes in the complement. Q-banding was useful to characterize some large B chromosomes with intercalary and subtelomeric bands as well as entirely positive short arms in some small submetacentric chromosomes. Nucleolar organizer regions have been identified in four pairs of chromosomes by silver staining.