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The peritrophic membrane of the female sandfly Phlebotomus papatasi
K Blackburn1, K R Wallbanks, D H Molyneux
1Department of Biological Sciences, University of Salford, U.K.
Abstract:
The ultrastructure of the peritrophic membrane of the female sandfly Phlebotomus papatasi has been studied at various times after blood meals. The membrane begins to form within four hours of the blood meal with the secretion by the entire midgut epithelium of an electron-dense amorphous material. Subsequently, the membrane is stabilized and strengthened by the production of a layer of irregular chitinous microfibres, the whole membrane then forming a complete and resilient sac apparently unaffected by boiling 9 M potassium hydroxide. The membrane appears redundant 48 hours after the blood meal and fragments, possibly as a result of chitinase activity. The membrane's main functions are probably the prevention of clogging of the microvillous brush border by the blood meal and the confinement of large proteins, particularly serum trypsin inhibitors, to the endoperitrophic space while allowing sandfly proteases access to the blood meal periphery. Blood is not required to stimulate membrane production. Saline taken by blood feeding into the midgut also stimulates membrane formation. Phlebotomus papatasi females may lack an efficient anticoagulant, at least in the midgut, as blood meals frequently include fibrin clots.
Insights
The sandfly peritrophic membrane forms rapidly after a blood meal, providing a protective barrier. This vital structure fragments later, suggesting a role for chitinase in its degradation.
Area of Science:
- Entomology
- Insect Physiology
- Sandfly Biology
Background:
- The peritrophic membrane is a dynamic structure in insect midguts.
- Its formation and function in sandflies, particularly Phlebotomus papatasi, are crucial for digestion and protection.
Purpose of the Study:
- To investigate the ultrastructural changes and formation timeline of the peritrophic membrane in female Phlebotomus papatasi after a blood meal.
- To elucidate the functional roles of the peritrophic membrane in sandfly digestion and midgut protection.
Main Methods:
- Ultrastructural analysis of the sandfly midgut at various time points post-blood meal.
- Observation of membrane formation, stabilization, and degradation processes.
Main Results:
- The peritrophic membrane forms within 4 hours of a blood meal, composed of amorphous material and chitinous microfibres.
- It protects the midgut epithelium and confines proteins, remaining resilient even after chemical treatment.
- Membrane formation is stimulated by both blood and saline, and it fragments around 48 hours, potentially due to chitinase.
Conclusions:
- The peritrophic membrane is essential for preventing midgut blockage and managing protein interactions during digestion in Phlebotomus papatasi.
- Its formation is not solely dependent on blood, and its eventual degradation is a programmed process.