Insect diuretic hormones
that regulate water balance
The insect excretory system
, responsible for regulating water balance in the insect, comprises the Malpighian tubules
and the hindgut
). Malpighian tubules secrete primary urine
, most of which is passed into the hindgut where water, ions
and essential metabolites are reabsorbed before the fluid is excreted. Excretion is under the control of diuretic
and anti-diuretic factors, or hormones
, comprehensively reviewed by Coast et al. (2002).
These factors are produced in neurosecretory cells
in the insect nervous system
, and stored and released from neurohaemal sites, such as the corpora cardiaca
in the brain
. Before a factor can be attributed with the role of hormone, it needs to meet certain criteria. While there is evidence that some diuretic and antidiuretic factors are indeed circulating neurohormones, this has not been demonstrated for all factors investigated so far.
It has been known for many years that insects possess diuretic and antidiuretic factors, but it has only been comparatively recently that technological advances have allowed for them to be characterised. Antidiuretic factors are less well studied than diuretic factors. They act either on the Malpighian tubules to inhibit urine production, or on the hindgut to stimulate reabsorption. To date, the only insect for which both diuretic and antidiuretic hormones (acting directly on tubules) have been isolated... Read More