A Small Reference..........

Subject: Integr. Comp. Biol.44: 21-27

The reference is ...

Rourke, BC

Geographic and altitudinal variation in water balance and metabolic rate in a California grasshopper, Melanoplus sanguinipes.

J Exp Biol. (2000) 203:2699-712.

... and the last paragraph from this paper is ...

"I have shown that WLR [water loss rate] varies among natural populations of grasshoppers and that the primary factors affecting WLR are the amount of cuticular lipid and its melting point. These data strongly support the classical theories of the importance of cuticular lipids to the permeability of the integument. Metabolic rate was also highly variable and strongly correlated with increasing elevation, but it is not a major factor in determining WLR. In contrast to arguments supporting the importance of a discontinuous gas-exchange cycle to respiratory water loss, this study finds no evidence for significant water savings through the discontinuous gas-exchange cycle."

My "increasingly" probably overstates the case but I wanted to point out that studies exist showing that discontinuous ventilation is not necessarily correlated with water savings.

R. Meldrum Robertson

Professor and Head

Department of Biology,

Queen's University,

3118 Biosciences Complex,

Kingston, Ontario,

K7L 3N6, Canada.

Tel: 613-533-6533

Fax: 613-533-6617

Email: robertrm@biology.queensu.ca

website: http://biology.queensu.ca/~locust/

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