Recta of desert locusts were mounted as flat sheets in ‘Ussing-type’ chambers and various parameters of tissue viability were monitored. The trans-epithelial resistance, the electropotential difference, the short-circuit current (Isc), and unidirectional fluxes of 22Na+, 36C1 and 42K+ all remained relatively constant during the 3rd and 4th h.

The direction of the Isc indicated a net transport of either anions to the haemocoel, or cations to the lumen side. This current was abolished by KCN and was sensitive to temperature (Q10 = 2.4).

There was a rapid decline in Isc over the first 2 h, which could be abolished by substituting NO3 or SO42- for Cl in the bathing medium, indicating that this fall in current is due to a decline in the rate of Cl transport. Measurements of 36C1 fluxes under short-circuit conditions confirm this interpretation.

In the steady-state (3rd and 4th h), however, the same anion substitutions had no effect on IsC. Concurrent flux measurements indicated that net Na+ and K+ transport to the haemocoel side equals or slightly exceeds that of C1 in the same direction. Consequently all of the Isc must be due to unidentified ion transport processes. Transport of H+ to the lumen, or HCO3 and organic anions to the haemocoel side, is proposed.

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