Control of diuresis in the yellow fever mosquito Aedes aegypti: Evidence for similar mechanisms in the male and female

Abstract

This study was undertaken to determine whether males of the mosquito Aedes aegypti have diuretic mechanisms similar to the female, even though males do not take blood meals and, therefore would not seem to require mechanisms for rapid diuresis. In particular, the effects of secretagogues extracted from female and male mosquito heads on the Malpighian tubules of both sexes were tested. Male Malpighian tubules are considerably smaller than female tubules and they secrete Na, Cl and water in vitro at 1 6 the rates of female tubules. However, the concentrations of Na, K and Cl are similar in fluid secreted by female and male tubules. The female head extract significantly increases Na, Cl and water secretion in tubules of both sexes. Likewise, the male head extract significantly increases Na, Cl and water secretion in tubules of both sexes. K secretion by female tubules increases after treatment with female extract but decreases after treatment with male extract. K secretion by male tubules is not affected by female or male extracts. Female and male head extracts also share the same effects on transepithelial voltage and resistance across isolated perfused Malpighian tubules. Cyclic AMP, a known stimulator of Na, Cl and water secretion in female Malpighian tubules also significantly increases Na, Cl and water secretion in male tubules. Therefore, Malpighian tubules of the male and female mosquitoes appear to have similar ion transport mechanisms for NaCl and fluid secretion as well as similar diuretic hormones and receptors. Only quantitative differences exist between secretion of Na, Cl and water in the male and female mosquito, reflecting the larger NaCl and fluid loads consumed by the female.