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Title: Osmoregulatory Organs of Immature Culicodes Sonorensis (Diptera: Ceratopogonidae)

item Reeves, Will

Submitted to: Entomological News
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2008
Publication Date: 11/18/2008
Citation: Reeves, W.K. 2008. Osmoregulatory Organs of Immature Culicodes Sonorensis (Diptera: Ceratopogonidae). Entomological News, Vol. 119: 371-374

Interpretive Summary: Insects larvae that live in the wet or water saturated soils of livestock feed lots or near watering troughs include the biting midge that transmits bluetongue and epizootic hemorrhagic disease of deer. Insects that live in water must be able to control their intake of salts. Freshwater insects loose salts to the water and insects in salty water must get rid of salts from their blood. The larvae of these biting midges have special organs to exchange salts with their environment. The three organs in larvae of a biting midges that exchange chloride salts are described. These organs might be targeted by pesticides or significant in determining habitat characteristics.

Technical Abstract: The water saturated soils and wet feces in livestock feed lots support a variety of Diptera including Musca spp. and Culicoides spp. Aquatic insects that must regulate the ion concentrations of their haemolymph; and fresh water insects tend to loose ions to their aquatic environment. The larvae of Culicoides spp. presumably use their anal papillae for osmoregulation but some species lack these organs. The osmoregulatory organs of larvae and pupae of C. sonorensis have not been previously reported. Presumably these organs are similar to those reported for C. nubeculosus. The osmoregulatory organs of larvae of C. sonorensis are described. Tissues that actively transported ions were stained using a silver salt to detect active chloride exchange. In the larvae of C. sonorensis there were three distinct organs that were used for ion exchange. These included the anal papillae, chloride cells, and the hindgut. The anal papillae were previously known as osmoregulatory in other Nematocera. Chloride cells were scattered over the body of the larval C. sonorensis. In addition to these external organs the hindgut was lightly stained. The hindgut reduced silver salts but not at the same rate as the anal papillae or chloride cells. All of these organs are most likely involved with osmoregulation and the uptake of ions from the environment.