Mechanism of Insecticide-induced Diuresis in Rhodnius

Abstract

WATER conservation is critical for insects because of their large surface area relative to volume and the generally arid environment in which they live. Their survival depends on the waterproofing mechanism of the cuticle and the control of excretory and respiratory mechanisms which lead to water loss. There are indications that the critical water balance is disrupted by poisoning with certain insecticide chemicals^1–4, but the physiological basis for this action has not previously been defined. Treatment of Rhodnius with DDT results in the accumulation of a large volume of fluid in the rectum¹. We have now established that paralytic doses of compounds, representing each of the major types of insecticide chemicals, initiate massive excretion of fluid into the rectum of Rhodnius. Furthermore, the underlying mechanism involves the release of diuretic hormone, possibly from a bound form in the central nervous system, into the haemolymph where it contacts the Malpighian tubules and greatly increases their rate of secretion.