General Considerations on the Karyotypic Evolution of Chelonia from the Amazon Region of Brazil

Abstract

In comparison with other orders of Reptilia, there have been very few reports on the chromosomes of Chelonia in the recent literature. Van Brink (1959) described the chromosomes of Emys orbiculares and Chrysemys bellii bellii, both with a diploid number of 50 with macro and microchromosomes. Later, Sasaki and Itoh (1967) described identical karyotypes for Clemmys japonica and Geoclemmys reevesii, with a diploid number of 52, including many microchromosomes. Ayres et al. (1968, 1969) described two kinds of the diploid number, 28 for P. cayennensis, P. expansa, P. unifilis and P. sextuberculata, and 26 for P. dumeriliana. These same numbers were described by Huang and Clark (1969) for P. unifilis and P. expansa. These species do not have microchromosomes, their diploid number being very low in comparison to other species already studied. Sampaio et al. (1969, 1971) described the karyotypes of Geochelone carbonaria and G. denticulata, both with 52 chromosomes. The karyotypes are identical except for no. 12 pair which differed in having pericentric inversion. The karyotype of G. carbonaria is identical to that of Clemmys japonica and Geoclemmys reevesii described by Sasaki and Itoh (1967). Barros et al. (1970, 1972) found 56 chromosomes in the subspecies Kinosternon scorpioides scorpioides and K. s. carajasensis. These two subspecies have a karyotype very similar to that of Geoemyda punctularia punctularia, with the same diploid number. The differences between them could well be explained by pericentric inversions (Barros et al. 1973). © 1976, Japan Mendel Society, International Society of Cytology. All rights reserved.