Pupal shape and size dimorphism in Aedes albopictus (Skuse, 1894) (Diptera: Culicidae)

Abstract

Aedes albopictus (Skuse, 1894) is a culicid mosquito associated with the transmission of pathogens causative for dengue, yellow fever, chikungunya, Mayaro and other diseases. Several recent studies have proposed that demographic surveys of dengue vector pupae are more useful than traditional larval indices for estimating populations. Geometric morphometrics is a tool for describing phenotypic variation that has been validated for characterizing sexual dimorphism. We undertook to apply this method to describe sexual and morphological dimorphism in A. albopictus pupae. Two-dimensional co-ordinates were digitalized from 60 specimens in two stages using 10 landmarks in pupae and 14 in wings. Configuration matrices were aligned by generalized procrustes analysis to extract matrix configurations and centroid size (CS). A discriminant analysis (DA) was used to test group (female or male) membership significance, and non-parametric ANOVA was used for CS differences. We found significant differences (Kruskal-Wallis P < 0.01) among pupal cephalothorax CS and adult wings; female pupae and adults were larger than males. The DA for cephalothorax and wing specimens showed significant differences (Hotelling P < 0.0001) between females and males. Through cross-validation, females and males were correctly classified with greater than 90% accuracy using the conformation characteristics described. Our study is the first description of phenotypic variation of pupal shape and size in A. albopictus laboratory colonies, and the results can be used as an additional tool in dengue entomological survey programs. More studies are necessary to confirm the variation between natural and laboratory populations