Lectin and peritrophic membrane development in the gut of Glossina m.morsitans and a discussion of their role in protecting the fly against trypanosome infection

Newly emerged Glossina m.morsitans Westwood tsetse flies lack a peritrophic membrane which develops to fully line the midgut after c. 80-90 h. Midgut lectins are mainly associated with the peritrophic membrane. Lectin levels in the blood-free gut of adult flies rise slowly up to 8 days and then rapidly to at least 14 days post-eclosion (when the last of our recordings was made). Despite starving flies for 4 days prior to the agglutination assay, gut lectin levels in older flies are 100-200 times more than those in newly ecloded flies. This is inconsistent with the idea that there is a simple relationship between lectins and the protection of tsetse flies against trypanosome infection. Various theories put forward to account for age-dependent variation in the ability of tsetse to become infected with trypanosomes are discussed in the light of these findings.