Plant sucking heteropteran bugs feed regularly on small amounts of K(+)-rich plant material, in contrast to their hematophagous relatives which imbibe large volumes of Na(+)-rich blood. It was anticipated that this would be reflected in the endocrine control of Malpighian tubule (MT) secretion. To explore this, neuroendocrine factors known to influence MT secretion were tested on MT of the pentatomid plant sucking stink bugs, Acrosternum hilare and Nezara viridula, and the results compared with previously published data from Rhodnius prolixus. Serotonin had no effect on N. viridula MT, although it stimulates secretion by R. prolixus MT >1000-fold, and initiates a rapid diuresis to remove excess salt and water from the blood meal. Kinins had no effect on stink bug MT, but secretion was increased by Zoone-DH, a CRF-like peptide, although the response was a modest 2-3-fold acceleration compared with 1000-fold in R. prolixus. Native CAPA peptides, which have diuretic activity in dipteran flies, had antidiuretic activity in MT of the stink bug (Acrhi/Nezvi-CAPA-1 and -2), as previously shown with Rhopr-CAPA-2 in R. prolixus. The antidiuretic activity of Rhopr-CAPA-2 has been linked with terminating the rapid diuresis, but results with stink bugs suggest it is a general feature of heteropteran MT.
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