Apparent feeding behaviour of ensheathed third-stage infective larvae of human hookworms

The third-stage ensheathed infective larvae (L3) of hookworms are reputed to be non-feeding stages, and the L2-derived sheath is considered to be a barrier to macromolecular uptake and secretion. During a study of the lectin-binding characteristics of en- and exsheathed L3 larvae of Ancylostoma duodenale, fluorescein isothiocyanate conjugated lectins (con A and Ulex europaeus agglutinin) were repeatedly seen in the oesophageal lumen, as well as on the surface of L3 larvae encased in the L2 sheaths. Repetition of these experiments using Necator americanus L3 larvae yielded similar results. These observations suggest that ensheathed hookworm larvae can obtain/utilise and secrete macromolecules, despite the presence of a sheath.