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Journal of Experimental Biology 101,171-186 (1982)
Published by Company of Biologists 1982

Active HCO₃- Secretion in the Rectal Salt Gland of a Mosquito Larva Inhabiting NaHCO₃-CO₃ Lakes

K. STRANGE ¹, J. E. PHILLIPS ¹, and G. A. QUAMME ¹

¹ Departments of Zoology and Medicine, University of British Columbia, Vancouver, British Columbia V6T 2A9, Canada

Aedes dorsalis larvae are one of the few organisms capable of inhabiting hypersaline NaHCO₃-CO₃ lakes. Under laboratory conditions larvae can survive and develop normally in saline media with pH values of 10.5, HCO₃² concentrations of 250 mM, or CO₃ ^2- concentrations of 100 mM.

Despite ingestion of alkaline media at a rate equal to 130% of larval body wt/day, these insects regulated haemolymph pH (7.55–770) and HCO₃- concentration (8.0–18.5 mM) within narrow limits.

Analysis of fluid obtained by micropuncrure or microcannulation indicated that rectal secretion is an important mechanism of pH and HCO₃- regulation.

The lumen-to-haemocoel HCO₃- and CO₃^2- gradients generated by isolated, microcannulated recta were 21:1 and 241:1, respectively.

Transepithelial potential in cannulated recta was –4.2 to –25.3 mV (lumen negative), demonstrating that net HCO₃- secretion occurs against a large electrochemical gradient.

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