Parasitology

Biography

Biography: Daniel Frías Lasserre

Abstract

In Chile, there are three endemic species of the genus Mepraia vectors of Trypanosoma cruzi, the causal agent of Chagas disease. In all these species, females are always wingless, but males can be winged or wingless according to species. The males of M. gajardoi they are always brachypterous. Males of M. parapatrica are braquipterous and macropterous and males of M. spinolai are macropterous, and also micropterous. Chromosome studies indicate that genes that govern the thoracic development and the development of the wings are located on the Y chromosome. A break of this holocentric chromosome would have giving rise to a Neo Y without the genetic information necessary to complete the development of the thorax and wings. This genomic event would explain the emergence of wingless males in M. spinolai. These species have a clinal distribution from north to south of Chile. This suggest a parapatric model of speciation. Thus, M. gajardoi is distributed in the coastal area of the regions XV and II of northern Chile. This is principally a sylvatic species that lives associated with seabirds, lizards, and wild rodents. M. parapatrica is distributed in the coastal area in region III and in the southern border the region II and also is associated with seabirds but also invades peridomestic habitats. M. spinolai distributed in interior valleys of Regions III, IV, V and in rural areas of Metropolitan region. This specie feeds mainly on small sylvatic mammals, invades the peridomestic habitats and also invades the human houses, especially in rural areas increasing the chances that these insects transmit T. cruzi to humans. In M. spinolai the frequency of micropterous and macropterous males depends according to the habitat where this species occurs. So in wild populations of Metropolitan region (Til-Til and Colina), the frequency of micropterous males is higher than in macropterous males. In contrast, in peridomestic habitat of region IV (Combarbalá), associated with goat pens, the frequency of macropterous males is greater than the frequency of micropterous males. Morphological analysis from the individuals of the collection of Institute of Entomology shows that the males collected inside of human houses in the Metropolitan region (Til-Til) and region IV (Combarbalá and Ovalle) indicates that are all macropterous. Similarly, male specimens were collected in 2012, 2013 and 2014 inside human habitation by staff of the Ministry of Health in the Region Metropolitan Region (TIL-Til), and also in Regions V, IV and III. These data show that from a total of 540 adults collected inside houses, 86.9 % are males winged and only 13.1 % are wingless (0.9 % are males micropterous and 12.2% females). The micropterous males are found almost exclusively in wild populations. This indicates a disruptive selection where the winged males migrate into human habitations and micropterous males remain in the wild populations. This situation is probably due to that the presence of wings implies a greater accumulation of heat, acting as a greenhouse effect. For this reason the winged males they go in search of cooler places inside houses where to take refuge and also can feed on blood human or domestic animals.