What is the association of heme aggregates with the peritrophic matrix of adult female mosquitoes?

The aim of this Letter is to call attention to the presence of iron-containing or heme aggregates seen within or near the peritrophic matrix (PM) in published Anopheles gambiae and Aedes aegypti midgut micrographs. The micrographs shown here suggest that the PM of An. gambiae adult female is not a homogenous layer and instead may have a peritrophin layer surrounded by heme aggregates that are possibly associated to other molecules involved in their formation. In depth studies addressing PM structure in different mosquito species are needed, as these will be important to continue clarifying the roles of the PM.