Title: LOCALIZATION OF MYOSUPPRESSIN-LIKE PEPTIDES IN THE HYPOCEREBRAL GANGLION OFTWO BLOOD-FEEDING FLIES: THE HORN FLY, HAEMATOBIA IRRITANS, AND THE STABLE FLY, STOMOXYS CALCITRANS (DIPTERA: MUSCIDAE)
Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 1995
Publication Date: N/A
Interpretive Summary: A major USDA research initiative is directed toward development of alternative pest management strategies that lead to reduction in current high levels of hazardous chemicals used to protect livestock from blood- feeding insects. One of the new types of pesticides focuses on compounds that act by disrupting the vital functions of neuropeptides produced by insects. Neuropeptides are small chains of amino acids that regulate many vital life functions. One part of the nervous system of insects has been found to regulate reproduction, feeding, and digestion. One of the main components of this system, the hypocerebral ganglion (located just under the brain), has been shown in this study to contain nerves that produce neuropeptides which have the unique function of inhibiting contraction of insect muscle. Processes of these nerves extend to the muscles of the insect digestive tract and to the wall of the heart where their products are released and regulate the function of these organs. Knowledge of the presence of these neuropeptides in these vital organs will help in developing practical methods of controlling horn flies and stable flies.
The insect peptides leucomyosuppressin (pEDVDHVFLRFamide) isolated from the cockroach, Leucophaea maderae, and dromyosuppressin (TDVDHVFLRFamide) from Drosophila melanogaster, have identical chemical sequences with the exception of the N-terminal amino acid and both inhibit spontaneous contraction of insect visceral muscles. Neurons in the hypocerebral ganglion of the horn fly, Haematobia irritans, and the stable fly, Stomoxy calcitrans, were found to contain material immunoreactive to the C-terminal of leucomyosuppressin but not to the N-terminal of dromyosuppressin. Two large lateral clusters containing eight cells, linked dorsally and ventrally by two chains of six cells, encircle the anterior surface of the proventriculus and were found to be immunoreactive to leucomyosuppressin and FMRFamide antisera. Axons from these cells were traced to the wall of the aorta and over the surface of the proventriculus. Ultrastructural analysis revealed these cells to contain a singular type of elementary secretory granule that contains material of relatively low electron density, both in the cell body and at the axon terminals.