Chromosome characterization of decapod crustacean species by fluorochrome- and restriction endonuclease- banding.

Chromosome characterization of decapod crustacean species by fluorochrome- and restriction endonuclease- banding. A.M. Deiana*, S. Salvadori*, E. Coluccia*, A. Milia**, R. Cannas*, A. Cau* *Dipartimento di Biologia Animale ed Ecologia, **Dipartimento di Biologia Sperimentale, Università di Cagliari, V.le Poetto,1 09126 Cagliari, Italy. The scanty information so far available on the karyology of Decapoda is mainly due to the technical constraints in obtaining good chromosomal preparations and to the low number of reports on banding techniques. The studied species have high diploid numbers of mainly small and meta-submetacentric chromosomes. Almost all chromosome numbers have been obtained from spermatogonial and spermatocitary plate counts. Restriction endonuclease (RE) banding localizes heterochromatic regions and allows a more sensitive analysis of constitutive heterochromatin than does C-banding. In fact REs attack the DNA at specific sequences and identify subclasses of repetitive DNA sensitive/resistant to their action. In particular, in Nephrops norvegicus and Palinurus elephas, C- and restriction endonuclease-banding have been a useful tool in sharply differentiating the chromosomes, clearly identifying the meiotic figures and pointing out the presence of supernumerary chromosomes which account for the chromosome variability. Heterochromatin analysis can be improved by using fluorochrome dyes that bind the DNA with a different specificity. Quinacrine and DA-DAPI allowed the identification of AT rich clusters in the genome of N. norvegicus, P. elephas and Scyllarides latus.