Continuous recording of excretory water loss from Musca domestica using a flow-through humidity meter: hormonal control of diuresis.
Water loss from adult male houseflies was continuously recorded using a flow-through humidity meter, which enabled losses to be apportioned between the sum of cuticular and respiratory transpiration, salivation and excretion. Transpiration accounted for >95% of water lost from sham-injected flies, compared with excretion (3.0%) and salivation (2.4%). In contrast, excretion accounted for 40% of water lost from flies injected with > or =3 microl of saline, whereas salivary losses were unchanged. Saline injections (1-5 microl) expanded the abdomen in the dorsal-ventral plane, and this expansion was positively correlated with the magnitude of the ensuing diuresis, suggesting the signal for diuretic hormone release originates from stretch receptors in abdominal tergal-sternal muscles. The effects of decapitation, severing the ventral nerve cord within the neck or ligaturing the neck, showed the head was needed to initiate and maintain diuresis, but was neither the source of diuretic hormone nor did it control the discharge of urine from the anus. These findings indicate the head is part of the neural-endocrine pathway between abdominal stretch receptors and sites for diuretic hormone release from the thoracic-abdominal ganglion mass. Evidence is presented for Musdo-K having a hormonal role in the control of diuresis, although other neuropeptides may also be implicated.
Coast
Geoffrey M
GM
Department of Biology, Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK. g.coast@bbk.ac.uk
D000818:Animals; D004231:Diuresis / Q000187:drug effects / Q000502:physiology; D006793:Houseflies / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D006813:Humidity; D007301:Insect Hormones / Q000502:physiology*; D008297:Male; D009479:Neuropeptides / Q000502:physiology; D012472:Salivation; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors; D014556:Urine; D014867:Water / Q000378:metabolism; D014870:Water Loss, Insensible / Q000502:physiology*
D007301:Insect Hormones; D009479:Neuropeptides; D014867:Water; D012965:Sodium Chloride