Fig. 1

Haemoglobin digestion in mosquitoes and ticks. a Host erythrocytes undergo lysis and release haemoglobin (Hb) and other proteins in the lumen of the midgut (1). In mosquitoes, proteases are secreted in the gut lumen for initial Hb extracellular digestion (2), generating peptides that will be further internalized and hydrolyzed in the epithelial cells (3). b In ticks, Hb is internalized by receptor-mediated endocytosis (2) and directed to large endosomal vesicles that fuse with lysosomes containing cysteine and aspartic proteases where it is degraded (3). Upon degradation of Hb, free heme must be detoxified (4)