Mitochondrial DNA variation reveals the presence of two management units in the sábalo Prochilodus lineatus (Characiformes: Prochilodontidae) from La Plata River basin

The La Plata River basin, the second largest drainage basin in South America, supports important fisheries, in which the sábalo Prochilodus lineatus is the leading species measured as extracted volumes. To characterize the population structure of the sábalo in the middle and lower regions of the La Plata River basin, cytochrome b DNA sequences of 121 samples collected in La Plata, Paraná and Uruguay rivers were used. Results suggest the presence of at least two populations: one that we called “southern population” uses the La Plata River and the lower sections of the Paraná and Uruguay rivers and another population (called here “northern population”) in the middle section of the Uruguay and Paraná rivers. The southern population would have a larger effective population size and coalescence-based analyses reveal an asymmetric gene flow, mainly from north to south. A striking result is that samples from the middle sections of the Paraná and Uruguay rivers are more alike to each other than they are to the other samples of their respective rivers. This similarity could be explained by historical reasons, probably as a consequence of the proximity that both rivers had until 100,000 years ago. The presence of different management units being exploited by the continental f

Genomic Changes of Chagas Disease Vector, South America

We analyzed the main karyologic changes that have occurred during the dispersion of Triatoma infestans, the main vector of Chagas disease. We identified two allopatric groups, named Andean and non-Andean. The Andean specimens present C-heterochromatic blocks in most of their 22 chromosomes, whereas non-Andean specimens have only 4–7 autosomes with C-banding. These heterochromatin differences are the likely cause of a striking DNA content variation (approximately 30%) between Andean and non-Andean insects. Our study, together with previous historical and genetic data, suggests that T. infestans was originally a sylvatic species, with large quantities of DNA and heterochromatin, inhabiting the Andean region of Bolivia. However, the spread of domestic T. infestans throughout the non-Andean regions only involved insects with an important reduction of heterochromatin and DNA amounts. We propose that heterochromatin and DNA variation mainly reflected adaptive genomic changes that contribute to the ability of T. infestans to survive, reproduce, and disperse in different environments

New records of Lepidochelys olivacea (Eschscholtz, 1829) (Testudines, Cheloniidae) provide evidence that Uruguayan waters are the southernmost limit of distribution for the species in the western Atlantic Ocean

We report 8 new records of Lepidochelys olivacea marine turtle in the Uruguayan waters, indicating this area as the southernmost limit of distribution for this species in the western Atlantic Ocean. In addition, 1 specimen was subjected to genetic analysis, revealing its population origin in the western Atlantic nesting colonies (Surinam, French Guiana, and Brazil). This report represents an update of the distribution of L. olivacea in the southwestern Atlantic and provides insight into the morphological and genetic characterization of the species at temperate waters