Variação temporal da composição genética de tartarugas cabeçudas (Caretta caretta, Linnaeus 1758) encalhadas no litoral sul do Brasil

Abstract

The loggerhead turtle, Caretta caretta (Linnaeus, 1758), in Brazil, is the most abundant species of turtle in the number of nests, it has a high level of philopatry, and there is evidence of the use of warm ocean currents to undertake long migrations. There are few records of their feeding areas, but the Elevação do Rio Grande (ERG) is postulated to be the main feeding-ground for loggerheads on the Brazilian coast. The present study aimed to characterize genetically, based on the Mitochondrial Control Region, turtles Caretta caretta from the southern coast of Rio Grande do Sul, victims of beaching between the years 2004 and 2007. We also analyzed the variation in genetic composition over the years and the origin of the samples was identified in relation to its spawning area compared to haplotypes described in the literature. Among the 58 sequences obtained, eight haplotypes were found, subjected to phylogenetic analysis by maximum likelihood methods and Neighbor-joining. We noticed that one of the haplotypes (LO) belongs, in fact, to the lineage of olive turtle, Lepidochelys olivacea (Eschscholtz, 1829). It was removed from subsequent analyzes because of suspected hybridization between C. caretta and L. olivacea, which is already reported in the literature. Other haplotypes were grouped with three haplotypes known under the Archie Carr Research Center for Sea Turtle (ACCSTR) CC-A2.1, CC-A4.1and CC-A4.2, while the remaining four showed no identity with any other previously established, and were considered as new (X1, X2, X3 and X4). The estimate of genetic differentiation based on nucleotide diversity showed that there is no significant difference between the analyzed years (X2 = 17.627; df = 18, p = 0.4805). Through networks haplotypes was compared between fragments of 800 and 380 base pairs (bp), the first being much more informative for analysis of populations, showing a greater number of polymorphisms. However, identification of the origin of the subjects was only possible by using the haplotypes of 380 bp, as the information on the larger fragment is still scarce. Three sources were observed for individuals sampled, by comparing them with haplotypes already defined in ACCSTR: 91.37% of Brazil, 3.45% from North Atlantic and 3.45% from Pacific. It was concluded that the region of Elevação do Rio Grande as well as presenting a high incidence of individuals from Brazil, presented several new haplotypes, whose spawning grounds are not known, thus underscoring the importance of conservation, also from feeding areas. The presence of individuals in the North Atlantic and the Pacific supports the use of warm sea currents for longdistance migration