SIMPLE DNA REPEATS AND SEX-CHROMOSOME DIFFERENTIATION IN ASELLUS-AQUATICUS (CRUSTACEA, ISOPODA)

The crustacean isopod species Asellus aquaticus does not usually have recognizable sex chromosomes. We previously identified a Y chromosome marked by two heterochromatic bands in some males of a population from the Sarno river near Naples. In this work we used oligonucleotide pro bes to test the presence and possible sex-specific distribution of fiv e simple repeat motifs in the genome of male and female individuals fr om the Sarno population The five oligonucleotide probes were hybridize d to enzyme-restricted genomic DNAs and the chromosome location of two probes was tested using fluorescence in situ hybridization. Our resul ts show that only the (TCC)(n) repetitive simple sequence has a sex-sp ecific hybridization pattern and presents a significant accumulation o n the Y chromosome in the region included between the two heterochroma tic areas. Moreover the GGAAT sequence is not present in the genome of A. aquaticus in any detectable quantity.