Green turtle (Chelonia mydas) genetic diversity at Paranaguá Estuarine Complex feeding grounds in Brazil.

Sea turtles are marine reptiles that undertake long migrations through their life, with limited information regarding juvenile stages. Feeding grounds (FGs), where they spend most of their lives, are composed by individuals from different natal origins, known as mixed stock populations. The aim of this study was to assess genetic composition, natal origins and demographic history of juvenile green turtles (Chelonia mydas) at the Paranaguá Estuarine Complex (PEC), Brazil, considered a Natural World Heritage site. Tissue samples of stranded animals were collected (n = 60), and 700 bp mitochondrial DNA sequences were generated and compared to shorter sequences from previously published studies. Global exact tests of differentiation revealed significant differences among PEC and the other FGs, except those at the South Atlantic Ocean. Green turtles at PEC present genetic signatures similar to those of nesting females from Ascension Island, Guinea Bissau and Aves Island/Surinam. Population expansion was evidenced to have occurred 20-25 kYA, reinforcing the hypothesis of recovery from Southern Atlantic refugia after the last Glacial Maximum. These results contribute to a better understanding of the dynamics of green turtle populations at a protected area by providing knowledge on the dispersion patterns and reinforcing the importance of the interconnectivity between nesting and foraging populations.

Evidence of an XX/XY sex chromosome system in the fish Dormitator maculatus (Teleostei, Eleotrididae)

The fish Dormitator maculatus has a chromosomes number of 2n = 46, females having a karyotype of 14 M, 28 SM, 2 ST and 2A and males 13 M, 28 SM, 3 ST and 2A. The presence of a heteromorphic pair in the males and a corresponding homomorphic pair in the females suggest the occurrence of an XX/XY sex chromosome system in D. maculatus. The putative X chromosome has a pericentromeric C-band positive segment and the putative Y chromosome a C-band positive short arm.

Molecular and immunocytogenetics of Brazilian fishes

Fish cytogenetics has incorporated during the last years new methodologies that employ molecular techniques, such as in situ hybridization with DNA probes for localization of chromosomal segments, chromosome banding using in situ digestion with restriction enzymes, in vivo incorporation of DNA base analogues, base-specific fluorochrome staining and, more recently, immunolabelling of chromosomes with antinucleoside antibodies. These techniques, associated with results obtained by using classical cytogenetic markers such as C-bands and nucleolus organizer regions, have allowed a more comprehensive understanding of the molecular structure of chromosomes and enlarged the area of cytogenetic evolutive studies. In neotropical fish the use of these modern techniques resulted in the localization of rDNA segments and the analysis of their activity; the localization of telomeric DNA segments; the identification of C-band modified patterns in species analyzed by in situ digestion of chromosomes with restriction endonucleases; the identification of R-handing patterns after incorporation of 5-bromodeoxyuridine; and, using the antibody antimethylcytosine, the identification of the methylated state of the heterochromatin in diploids and triploids.