Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/1996
Publication Date: N/A
Interpretive Summary: The stable fly is a major pest of livestock and other animals, especially cattle that are held in confinement. Because the stable fly is a worldwide pest that causes heavy economic losses each year, it is essential to search continuously for new or improved methods for its control. An effective systematic approach to the development of novel chemical control agents depends upon a thorough understanding of physiological systems in the pest that will be targeted by new management technology. Current research is focusing on the development of ways to disrupt the functions of neuropeptides, natural hormonal agents which serve as indispensable chemical intermediates in the regulation of a variety of essential physiological functions of the stable fly. This report presents detailed information on the structural properties of the muscle system that moves the excretory ducts of the stable fly. The research provides important new information on certain characteristics of the pest's excretory system, a potentially vulnerable target for new chemical agents aimed at disrupting that critical life process. It is anticipated that novel chemicals which mimic the actions of the neuropeptides will be active at very low concentrations and highly selective for a specific pest, thus providing a new control technology that will be less harmful to the environment and to non target organisms than are conventional insecticides.
Technical Abstract: The four Malpighian tubules of the female stable fly were divided into an anterior dorsal and a posterior ventral pair. A marked structural divergence existed between the distal terminations of these two pairs. This divergence consisted primarily in the number and size of crystalline granules present in the respective distal regions. The terminal diameter of the dorsal tubules was at least twice that of the ventral tubules. Intrinsic muscles were only found in that short proximal section (ureter) of each pair of tubules that emptied into the midgut. Other regions of the tubules showed no evidence of a muscle sheath. The small intrinsic muscles (0.25 to 0.6 um in diameter) of the ureter were visible under Nomarski optics at high magnification (600 x). The muscle fibers were embedded in the basal regions of the large epithelial cells that line the lumen of the ureter. Occasionally, these muscles were arranged in a multilayered lattice. Myofibrils were separated into sarcomeres of irregular alignment with classical A (0.8 um in length) and I bands. The Z disk consisted of discontinuous rows of dense bodies, and in partially contracted muscle some myofilaments of the A band passed between the dense bodies of the Z bands. T-system tubules and the sarcoplasmic reticulum were sparse to non-existent.