Browsing by Author "Elder, John Franklin"
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- Chromosomal complements and variation in some Venezuelan annual killifishes (cyprinodontidae)Elder, John Franklin (Virginia Tech, 1988-05-05)Karyotypes of nine species of Venezuelan annual killifishes were compared. Karyotypic differences were found between species and between some genera. A chromosomal sexual dimorphism was found in Pterolebias hoignei (2N = 46). Males of this species possess a single large "Y" chromosome. No chromosomal divergence was detected among conspecific populations from different localities. Pterolebias hoignei and Pterolebias zonatus were found to differ both in diploid number (46 and 42 respectively) and in metacentric chromosome number (6 and 12 respectively). All Rachoviaspecies were found to have a diploid number of 44. Rachovia maculipinnisand R. brevis were found to differ from one another in metacentric chromosome number (20 and 12 respectively). Rachovia hummelincki and R. pyropunctata both possess metacentric chromosome counts of 10. No karyotypic differences were found between Austrofundulus transilis and Austrofundulus limnaeus (2N = 44, metacentrics = 12). Several populations of the latter although divergent in male color patterns, did not differ karyotypically. All species examined, except Rivulus stellifer, departed from the presumptive ancestral teleost diploid number of 48. The degree of chromosomal variation appears not to be as high among the New World as among the Old World annuals. This difference among lineages with similar life histories and reproductive strategies suggests that stochastic events have not played a major role in mediating chromosomal divergence in annual fishes.
- Molecular drive and population differentiation of satellite DNAs in Cyprinodon variegatusElder, John Franklin (Virginia Tech, 1993-02-05)The genome of the Atlantic sheepshead minnow, Cyprinodon variecratus (cyprinodontidae) contains at least two highly repetitive satellite DNA sequences. The major satellite sequence is present at roughly 106 copies per haploid genome. The basic repeating unit averages 170 bp in length, tandemly arranged, and is bracketed by a Hind III restriction site. The Hind III satellite has little or no sequence similarity with other fish satellite DNAs reported in the 1iterature. Comparative hybridization experiments detect related sequences in the genomes of several species of pupfish of the genus Cyprinodon as well as in some cyprinodontid species of the genera Jordanella and Floridichthys. No significant hybridization was detected with the New World species Cualac tesselatus and Megupsilon aporus or within species of the Old World genera Valencia and Aphanius.