ABSTRACT. DNA barcoding is a useful complementary tool for use in traditional taxonomic studies due to its ability to detect cryptic species, and may be particularly efficient in the identification of fish species. The fish fauna of the Itapecuru River represents an important fishery resource in the Brazilian State of Maranhão, although it is currently suffering increasing degradation as a result of anthropogenic impacts. Therefore, DNA barcoding was used in the present study to identify fish species and establish a database of the rich freshwater fish fauna of Maranhão. A total of 440 specimens were analyzed, corresponding to 64 species belonging to 59 genera, 31 families, and 10 orders. Overall, 92.19% of these species could be identified by DNA barcoding, and were characterized by low levels (average 0.80%) of intra-specific divergence. However, five species (Anableps anableps, Gymnotus carapo, Sciades couma, Pseudauchenipterus nodosus, and Leporinus piau) presented values of mean genetic divergence above 3%, indicating the existence of cryptic diversity in these fishes. The DNA barcoding approach permitted the analysis of a large number of specimens and facilitated the discrimination and identification of closely related fish species in the Itapecuru Basin.

The geographic distribution of Megalechis thoracata is extended to the basin of the Itapecuru River, based on a specimen collected in the Soledade stream, a tributary of the Itapecuru, located in the Inhamum Municipal Environmental Protection Area in Maranhão, Brazil.

Aedes aegypti is the principal vector of the arboviruses—yellow fever, dengue virus, chikungunya, and zika virus. Given the epidemiological importance of this mosquito, its capacity to adapt to different habitats, and its resistance to many types of control measures, systematic research into the genetic variability of the populations of this mosquito is one of the most important steps toward a better understanding of its population structure and vector competence. In this context, the present study verified the presence of distinct genetic lineages of Ae. aegypti in areas with high infestation rates, based on the analysis of microsatellite markers. The samples were collected in nine municipalities with high building infestation rates in the Mid-North region of Brazil. Six microsatellite loci were genotyped in the 138 samples, producing a total of 32 alleles, varying from one to nine alleles per locus in each of the different populations. The AMOVA revealed greater within-population genetic differentiation with high fixation rates. The general analysis of population structure, based on a Bayesian approach, revealed K = 2, with two Ae. aegypti lineages that were highly differentiated genetically. These data on the connectivity of the populations and the genetic isolation of the lineages provide important insights for the development of innovative strategies for the control of the populations of this important disease vector.