|Coudron, Thomas - Tom|
Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/27/2007
Publication Date: 1/1/2008
Citation: Habibi, J., Coudron, T.A., Backus, E.A., Brandt, S.L., Wagner, R.M., Wright, M.K., Huesing, J.E. 2008. Morphology and histology of the alimentary canal of Lygus hesperus Knight (Heteroptera: Cimicomoropha: Miridae). Annals of the Entomological Society of America. 101(1):159-171. Interpretive Summary: Current strategies for controlling pest insects involve the use of naturally occurring substances that enter the insect by penetrating the cuticle of the insect or by accompanying the food ingested by the insect. The complexity of the digestive system has often deterred scientists from considering the food stream as a way to deliver a substance to control an insect. This study characterized the anatomy of the digestive tract of a pest insect that pierces a plant and extracts nutrients from within. The detailed description of the tissue and cellular structure of the digestive tract were used as the basis to construct a model of the insect digestive system. With the aid of this model, scientists can now begin to develop concepts that include the food stream as a delivery system for substances to control insects. The model will be used by researchers to better understand the interactions of naturally occurring substances with the insect digestive system and to improve their selection of substances and enhance the effectiveness of those substances. The end result will be a reduction of the impact of the pest insect on agricultural crops.
Technical Abstract: Microdissection and transverse semi-thin sections were used to examine the cellular structure of the alimentary canal of Lygus hesperus Knight. The midgut had the most complex morphology and cellular structure, consisting of 3 major regions, the first (descending), second (ascending), and third (descending) ventriculi, and distinctly different epithelial cell types. The cell types included non-differentiated regenerative cells, which occurred throughout the midgut but were especially abundant in the anterior region of the first ventriculus, endocrine cells and columnar cells. Granular cells contained numerous opaque, small granules or concretions, and had short apical microvilli. Columnar cells possessed numerous, usually transparent, large vesicles and lipid spheres and had an extensive cell surface area in the gut lumen, with long apical microvilli. In addition, each cell type also varied in size, shape, concentration of brush border microvilli and location within the gut, especially with progression distally. The first ventriculus was composed of short endocrine cells and long, finger-like columnar cells. In comparison, the second ventriculus consisted of bulbous endocrine cells and shorter columnar cells, and the third ventriculus had longer endocrine cells and shorter columnar cells. We hypothesize that the midgut is structurally and functionally differentiated along its length, with each ventriculus representing a specialized zone of secretary/absorptive function. Application of this postulate allowed development of a digestion and absorption model in L. hesperus.