. Brimleyana. Zoology; Ecology; Natural history. Necturus Chromosome Evolution 41. N. alabamensis N. punctatus Fig. 1. Map showing approximate distribution of species of the genus Nectu- rus used in this study (adapted from Conant 1975). Specimens of N. beyeri from Texas have identical karyotypes to that of N. maculosus, with 12 (6 pairs) telocentric chromosomes (Fig. 5). As in the other species, two of these pairs of asymmetrical chromo- somes are medium-size, and the remaining telocentrics are small. The Y-chromosome of N. beyeri is also virtually identical to that of N. maculosus. A karyoty
. Brimleyana. Zoology; Ecology; Natural history. Necturus Chromosome Evolution 41. N. alabamensis N. punctatus Fig. 1. Map showing approximate distribution of species of the genus Nectu- rus used in this study (adapted from Conant 1975). Specimens of N. beyeri from Texas have identical karyotypes to that of N. maculosus, with 12 (6 pairs) telocentric chromosomes (Fig. 5). As in the other species, two of these pairs of asymmetrical chromo- somes are medium-size, and the remaining telocentrics are small. The Y-chromosome of N. beyeri is also virtually identical to that of N. maculosus. A karyotype and idiogram of N. maculosus were presented earlier (Sessions 1980), but a new C-band idiogram of this species was con- structed for this study (Fig. 3). It shows the position of the sex chromo- somes and the 6 pairs of telocentric chromosomes in the karyotype. The subtelocentric Y-chromosome of this species is more heterochromatic than that in any of the other species of Necturus (Fig. 4). DISCUSSION Our karyological data support previously reported electrophoretic evidence (Ashton et al. 1980) that N. lewisi, N. punctatus, and N. macu- losus are distinct, probably long-isolated species. These data further suggest that N. alabamensis, which has not been studied electrophoreti- cally, may represent another distinct species, and that N. beyeri is only a little-differentiated southern form of N. maculosus. Karyological evi-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original North Carolina State Museum of Natural History. [Raleigh, NC : North Carolina State Museum of Natural History]
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