A karyological study of turtles from the Brazilian Amazon Region

Abstract

The karyo types of five turtles of the genus Podocnemis from the Amazon Region of Brazil were determined. Four species, P. cayennensis, P. expansa, P. sextuberculata and P. unifilis have 28 (2n) chromosomes and one, P. dumeriliana, has 26 (2n). No morphologically distinguishable sex chromosomes could be observed. The difference in number in P. dumeriliana can be explained by the occurrence of a centric fusion. The chromosome numbers in this genus are extremely low when compared with the range previously found in Chelonia (2n = 50 to 64).

Highly conserved linkage homology between birds and turtles: Bird and turtle chromosomes are precise counterparts of each other

“…Turtles have variable numbers of chromosomes, ranging from 2n = 26 to 68 (Ayres et al 1969, Bickham & Baker 1976, Bickham et al 1983. The most common diploid number is around 50-52 in Emydidae, including 12-14 pairs of macrochromosomes and 12-14 pairs of microchromosomes, and 66 in Trionycidae, including 8-9 pairs of macrochromosomes and 24-25 pairs of microchromosomes (Bickham & Baker 1976, Bickham et al 1983.…”

The Chromosomes of Some Japanese Snakes, With Special Regard to Sexual Dimorphism

“…In contrast, any obvious sex-chromosome dimorphism was not detected in several species of turtles (Huang and Clark 1967;Sasaki and Itoh 1967;Ayres et al 1969) and lizards (Cohen and Clark 1967;Dallai and Urbani 1967;Itoh et al 1968). A comparable feature has also been suspected in crocodilians (Cohen and Clark 1967;Fishman et al 1968).…”

First Cytogenetic Study of Malayan Snail-eating Turtle, <i>Malayemys macrocephala</i> (Testudines, Geoemydidae) in Thailand

“…Turtle karyotypes show two general tendencies based on the presence or absence of microchromosomes, but still there is much variation between groups. For example, the chromosome number in the order Chelonia ranges from 2n=26 in Podocnemis dumeriliana (Ayres et al 1969) to 2n=96 in Platemys platycephala (Bull andLegler 1980, Bickham et al 1985). Moreover, while karyotypic studies have frequently been published for turtles from the suborder Cryptodira, information about Pleurodires is scarce and fragmented and mainly based on conventional staining techniques (Noleto et al 2006).…”

“…Information about karyotypes in turtles is scarce and fragmented, and usually based on conventional staining technique; only a few studies have been published, all of them recent (Ayres et al 1969, Bickham 1975, 1981, Bickham and Baker 1976, Bull and Legler 1980, Bickham et al 1985. This fact is probably due to the difficulty in obtaining samples for cytogenetic analysis in some species, or to problems in obtaining metaphase cells by cell culture induction.…”