42 



Stanley K. Sessions and John E. Wiley 



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Fig. 2a-d. C-banded mitotic preparations of Necturus species: a, N. lewisi; b, 

 W. punctatus; c, JV. alabamensis (8 telocentrics); d, iV. maculosus. Arrows indi- 

 cate Y-chromosomes. Scale = 10 micrometers. 



dence is also in accord with electrophoretic data in that N. lewisi and N. 

 punctatus are more similar to each other than either is to N. maculosus. 

 The karyological information, however, reveals additional details of 

 interrelationships that have not been resolvable by the electrophoretic 

 analysis. 



While all species of Necturus have the same diploid number of 

 chromosomes, they differ in the degree of karyotype asymmetry (Table 

 2). The species form two groups on the basis of presence or absence of 

 telocentric chromosomes: N. lewisi and N. punctatus have completely 

 bi-armed karyotypes, while N. maculosus, N. beyeri, and N. alabamen- 

 sis all have several pairs of telocentric chromosomes. In terms of 



