Ontogenetic changes in wild chagasic bugs (Dipetalogaster maxima): Exploring morphological adaptations in pre-adult and adult stages

Abstract

Triatomine insects are vectors of Trypanosoma cruzi (Chagas, 1909), the causing agent of Chagas disease. We studied the morphological ontogenetic changes of Dipetalogaster maxima (Uhler, 1894), an endemic Chagas vector of Baja California Sur, Mexico. We measured and compared among nymphal stages and adults and, between sexes phenotypic traits linked to the following functions: a) feeding: proboscis length and width; b) vision: head length and width; c) mobility: pronotum width and length and; feeding capacity and fecundity: abdomen length in 5 nymphal stages and in adults of both sexes, respectively. We found a steady increase in proboscis and head size. The length of pronotum, and abdomen increased abruptly in adults compared to the fifth nymphal stage. Adult females were only bigger than males in total length, whereas males had larger pronotum. Our results demonstrated a stable increase along the fifth stage, but an exaggerated increase of the pronotum when insects become adults. This growth is associated with wing muscular growth, potentially used for dispersal and finding mates and preys during adult life. In turn, fecundity is operating to enlarge female’s total length and abdominal size, but male abdomen may be selected to storage large blood meals.