Abstract
Examination of egg rafts from Cx. quinquefasciatus using electron microscopy revealed that the surface of individual eggs is made up of a series of cone-like tubercles surrounded by a mesh network of tubercle extensions. Rafts of eggs are held together by an extrachorionic secretion located between the tubercles and by mechanical interdigitation of tubercles. Mosquitoes exposed to sublethal doses of the insect growth regulator, methoprene, laid egg rafts that were less organized and more loosely constructed than those of females not exposed to methoprene. Eggs from treated females had shorter tubercles, and excess cementum coated the egg covering the mesh network that formed the air/water jacket used for respiration by the developing embryos. Consequently, hatchability was greatly reduced. The female accessory gland also was studied to investigate its role in the synthesis of egg raft secretions. The gland consisted of a layer of glandular epithelium surrounding a central lumen which connects to the common oviduct. Examination of the organelles within the gland cells indicated that they produce the extrachorionic secretion that helps hold the eggs together in the raft. The accessory gland differed in size and shape at different stages of the ovarian cycle, suggesting that its secretary activity was correlated with oviposition. Larval exposure to sublethal doses of methoprene affected the accessory glands of surviving females. The cells of the gland were more acidophilic than glands from untreated controls. Vacuoles began appearing in the cytoplasm of the accessory glands as the cementum was secreted faster than it could be produced by the gland. These effects on the female accessory gland, as well as on the development times, did not appear to be dosage dependent.
Hausser, Nicole Lynne (1995). Effects of sublethal methoprene dosages on egg rafts and reproductive tracts of female Culex quinquefasciatus say (Diptera: Culicidae). Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1995 -THESIS -H384.