Abstract:

 Circulation of water and nutrients in the midgut of Zonocerus variegatus was studied to determine the flux pattern and its possible implication in the adaptation of the insect to hydrogen cyanide. Histological sections of midgut cells were observed. Gradients of K⁺, Na⁺ and protein along midgut were determined. The permeability of midgut segments to K⁺, Na⁺, Ca²⁺, Mg²⁺ and methyl blue was observed. The midgut (ventriculus and gastric caeca) was histologically similar, and made of columnar cells with striated borders. The nutrients varied in concentration in the different midgut segments. The substances tested for permeability passed through the midgut segments. It was concluded that the entire midgut was involved in food and water absorption. There was no counter flow of fluids from the posterior midgut as in most orthopterans. One-way movement of the gut contents prevents accumulation of toxic substances to injurious levels, enabling the insect to favourably tolerate hydrogen cyanide in cassava leaves.

Key words: Zonocerus variegatus, midgut, nutrient, water, permeability, fluxes, uptake