Rectal Absorption in the Desert Locust, Schistocerca Gregaria Forskål

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Abstract
1. The histology of the rectum of Schistocerca gregaria is described. 2. A method is described whereby net absorption of water from the rectum (in situ, isolated by ligation) can be measured. 3. Water is actively absorbed from the lumen of the rectum against an osmotic gradient and in the absence of a significant net flux of solute. 4. The maximum osmotic gradient developed is 2-3 times greater in locusts supplied with hypertonic saline than in locusts supplied with tap water. This indicates some ability to regulate water absorption in relation to requirement. 5. The ionic concentration of rectal fluid and the rate of salt absorption from the lumen have little effect on the maximum osmotic gradient developed across the rectal wall. 6. Possible mechanisms of active absorption of water are discussed.