Endogenous glycoconjugates are not associated with filter feeding in mosquito larvae (Diptera: Culicidae)

Abstract

Histochemical techniques were used to determine the origin and possible function of glycoconjugates in the head of larval mosquitoes. Late instars of Aedes aegypti (L.), Aedes implicatus Vockeroth, Culex territans Walker, and Anopheles earlei Vargas were stained with Alcian Blue at pH 0.5, 2.5, and 3.2, aldehyde fuchsin, and periodic acid – Schiff's reagent. Lectins derived from Triticum vulgaris, Bandeiraea simplicifolia, Sophora japonica, Pisum sativum (PSA), and Ulex europaeus were used to determine the composition of the glycoconjugates present in the head of A. aegypti. Additionally, larvae were fed inert Dayglo®particles and stained as above to determine the origin of glycoconjugates observed in the gut. Examination showed that carboxylated and weakly and strongly sulphated glycoconjugates are secreted from what are described here as dorsal and ventral cephalic glands. With the exception of PSA, none of the lectins bound to the glands or their secretion product. Globular and elongate cells in the ventral cephalic gland bound PSA, indicating the presence of α-D-mannose. The secretion product is not used to enhance food capture or handling. Instead, it is hypothesized that these glycoconjugates aid in formation of mouthpart structures or facilitate ecdysis.