Salivary gland surface carbohydrate variations in three species of the Anopheles gambiae complex

Fluorescein isothiocyanate (FITC)-conjugated lectins (agglutinins) were employed as probes to distinguish between the various carbohydrates present on the surface of salivary glands of three species of mosquito of the Anopheles gambiae complex. Of twenty lectins tested, eight (Concanavalin A- Con A, Lathyrus odoratus- LOA, Lens culinaris, Pisum sativum-PSA, Vicia faba- VFA, Triticum vulgaris, Maclura pomifera- MPA and Ulex europaeus) specifically reacted with the salivary gland membrane. Both mannosyl and N-acetylglucosamine moieties were detected in the three Anopheles gambiae sensu stricto strains, the two An. arabiensis strains and a single An. merus strain examined. Variations in the degrees of fluorescent intensities of Con A and MPA in particular suggested interspecies differences in membrane mannosyl and galactosyl residues on the salivary gland lobes of the three mosquito species in this study. Furthermore, intraspecific variations in mannose as indicated by Con A, LOA, PSA and VFA staining were demonstrated between the An. gambiae s.s. strains. The use of either peroxidase-labelled or biotinylated lectins confirmed the binding specificities of the above lectins. The consistent differences observed in lectin binding suggest that variations occur in salivary gland surface carbohydrate residues and that lectins can be used to distinguish between at least some members of the An. gambiae complex.