Mitotic and meiotic chromosomes of the American lobster Homarus americanus (Nephropidae, Decapoda) Coluccia E., Cau A., Cannas R., Milia A., Salvadori S., Deiana A.M. Dipartimento di Biologia Animale ed Ecologia, Università di Cagliari, Viale Poetto 1, 09126 Cagliari, Italy. Homarus americanus H. Milne Edwards is an important target of North American commercial fishery. The very few karyological studies on this species have documented a remarkable intraspecific numerical variability of the chromosome complement; in order to explain this, the presence of supernumerary chromosomes has been hypothesised though not cytologically demonstrated (Roberts, 1969; Hughes, 1982). Supernumerary (B) chromosomes are additional chromosomes, highly polymorphic in number and morphology within populations and species, and their presence has already been shown in a species of the family Nephropidae (Deiana et al., 1996). In this study we characterise the mitotic and meiotic chromosomes of H. americanus by different banding techniques, and provide evidence of the presence of chromosomes, in this species, with some of the features of the B chromosomes. Chromosome preparations have been obtained from testicular tissue using an air-drying technique. C-banding, fluorochrome-banding and restriction enzyme-induced banding (RE) have allowed a clear identification of meiotic figures and the study of the distribution and structure of heterochromatic regions. These regions are localised on most centromeres and react specifically to the digestion with different REs and to the GC – and AT- specific fluorochrome stainings. Our results point out the GC richness of H. americanus heterochromatin, as shown by the bright fluorescence of most of heterochromatic regions after staining with the GC- specific fluorochrome, chromomycin A3. On the other hand, only few centromeric regions are fluorescent after staining with the AT-specific fluorochromes, DAPI, and Quinacrine. Furthermore the adopted techniques have revealed presence of small B chromosomes, completely heterochromatic, variable in number, and often asynaptic in first meiotic metaphase. The presence of these chromosomes can, at least partially, account for the numerical variability already observed in the karyotype of this species.
Mitotic and meiotic chromosomes of the american lobster Homarus americanus (Nephropidae, Decapoda).
COLUCCIA, ELISABETTA;CANNAS, RITA;
1999-01-01
Abstract
Mitotic and meiotic chromosomes of the American lobster Homarus americanus (Nephropidae, Decapoda) Coluccia E., Cau A., Cannas R., Milia A., Salvadori S., Deiana A.M. Dipartimento di Biologia Animale ed Ecologia, Università di Cagliari, Viale Poetto 1, 09126 Cagliari, Italy. Homarus americanus H. Milne Edwards is an important target of North American commercial fishery. The very few karyological studies on this species have documented a remarkable intraspecific numerical variability of the chromosome complement; in order to explain this, the presence of supernumerary chromosomes has been hypothesised though not cytologically demonstrated (Roberts, 1969; Hughes, 1982). Supernumerary (B) chromosomes are additional chromosomes, highly polymorphic in number and morphology within populations and species, and their presence has already been shown in a species of the family Nephropidae (Deiana et al., 1996). In this study we characterise the mitotic and meiotic chromosomes of H. americanus by different banding techniques, and provide evidence of the presence of chromosomes, in this species, with some of the features of the B chromosomes. Chromosome preparations have been obtained from testicular tissue using an air-drying technique. C-banding, fluorochrome-banding and restriction enzyme-induced banding (RE) have allowed a clear identification of meiotic figures and the study of the distribution and structure of heterochromatic regions. These regions are localised on most centromeres and react specifically to the digestion with different REs and to the GC – and AT- specific fluorochrome stainings. Our results point out the GC richness of H. americanus heterochromatin, as shown by the bright fluorescence of most of heterochromatic regions after staining with the GC- specific fluorochrome, chromomycin A3. On the other hand, only few centromeric regions are fluorescent after staining with the AT-specific fluorochromes, DAPI, and Quinacrine. Furthermore the adopted techniques have revealed presence of small B chromosomes, completely heterochromatic, variable in number, and often asynaptic in first meiotic metaphase. The presence of these chromosomes can, at least partially, account for the numerical variability already observed in the karyotype of this species.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.