Midgut of the non-hematophagous mosquito Toxorhynchites theobaldi (Diptera, Culicidae)

Abstract

In most mosquito species, the females require a blood-feeding for complete egg development. However, in Toxorhynchites mosquitoes, the eggs develop without blood-feeding, and both females and males exclusively feed on sugary diets. The midgut is a well-understood organ in blood-feeding mosquitoes, but little is known about it in non-blood-feeding ones. In the present study, the detailed morphology of the midgut of Toxorhynchites theobaldi were investigated using histochemical and ultrastructural methods. The midgut of female and male T. theobaldi adults consists of a long, slender anterior midgut (AMG), and a short, dilated posterior midgut (PMG). The AMG is subdivided into AMG1 (short, with folds) and AMG2 (long, without folds). Nerve branches and enteroendocrine cells are present in AMG and PMG, respectively. Compared with the PMG of blood-feeding female mosquitoes, the PMG of T. theobaldi is smaller; however, in both mosquitoes, PMG seems be the main region of food digestion and absorption, and protein secretion. The epithelial folds present in the AMG of T. theobaldi have not been reported in other mosquitoes; however, the midgut muscle organization and endocrine control of the digestion process are conserved in both T. theobaldi and blood-feeding mosquitoes.

A Gut Commensal Bacterium Promotes Mosquito Permissiveness to Arboviruses

“…Mosquitoes fed an equal amount of BSA with DENV and blood served as the mock controls. The mosquitoes were sectioned for periodic acid-Schiff staining at 2 hr post oral feeding (Godoy et al, 2015). Compared with the mock gut, the polysaccharide layer of mucin on the brush border (Godoy et al, 2015) was almost eliminated in the SmEnhancin-treated gut ( Figure 4F), further validating that SmEnhancin facilitated viral infection by digesting mucins on the mosquito gut epithelia.…”

Chitin distribution in the Oithona digestive and reproductive systems revealed by fluorescence microscopy

“…FITC is a green fluorescent protein that can be conjugated with a wheat lectin that has an affinity and specificity to N -acetyl-β- d -glucosamine ( Allen, Neuberger & Sharon, 1973 ). WGA-FITC staining is widely used for chitin detection by fluorescence, in a liquid medium containing lysed cells or directly on whole organisms ( El Gueddari et al, 2002 ; Farnesi et al, 2015 ; Fones, Mardon & Gurr, 2016 ; Godoy, Fernandes & Martins, 2015 ). On copepods, WGA-FITC was used only once; but after dissolution of the soft tissues which did not allow the investigation of the internal anatomy ( Mravec et al, 2014 ).…”

Chitin distribution in the Oithona digestive and reproductive systems revealed by fluorescence microscopy

“…FITC is a green fluorescent protein that can be conjugated with a wheat lectin that has an affinity and specificity to N-acetyl-β -D-glucosamine [23]. WGA-FITC staining is widely used for chitin detection by fluorescence, in a liquid medium containing lysed cells or directly on whole organisms [25][26][27][28]. On copepods, WGA-FITC was used only once before; but after dissolution of the soft tissues which did not allow the investigation of the internal anatomy [29].…”