Karyotype Evolutionary Diversification in Marine Fishes. First Classical and Molecular Cytogenetic Data on Four Atlantic Species

Fishes present an exceptional level of diversification among vertebrates, whose adaptive instructions contained in their genome are physically organised in their chromosomes. Although cytogenetic data are useful to help understand the evolutionary processes, they are restricted or unavailable for many fish families. Cytogenetic characteristics of one Atlantic member of the Kyphosidae, Cirrhitidae, Pempheridae and Bythitidae families - about which little or no prior data is known - are described here. Conventional chromosomal analysis and the mapping of the 18S and 5S ribosomal DNA sequences revealed substantial variations in the diploid number (2n = 38-48) and structure of the chromosomes (FN = 48-84; i.e. number of chromosome arms), as well as in the rDNA distribution (simple, multiple and polymorphic sites). The findings extend the cytogenetic data for reef fish groups across a wider phylogenetic range and reveal the various ways in which karyotype evolution has taken place in the marine environment.