Disruption of <i>Glossina morsitans morsitans</i> (Diptera: Glossinidae) eclosion behaviour: a novel method for evaluating the action of neurotoxic agents

AbstractAs the tsetse fly, Glossina morsitans morsitans Westwood extricates itself from the puparium and moves upward through the soil the ptilinum expands and contracts rhythmically and thus generates a stereotypic behavioural pattern that persists for up to 10 h if the tsetse fly remains confined. The response, which is easily recorded tensometrically from the movements of the ptilinum, can be exploited as a tool for evaluating the behavioral response of tsetse flies to various neurotoxic agents. The behavioural assay proves useful in providing precise information about the latency of the response and lethal time, and can suggest likely modes of action. For example, sublethal doses of pyrethroids reversibly suppressed the contraction cycles, a response consistent with the peripheral action of this insecticide. In contrast, chlorinated hydrocarbons greatly increased contraction frequency, a result consistent with the action of these agents on the central nervous system (CNS). Assays utilizing eight commercial insecticide preparations (Pybuthrin, K-othrin, Vaztak, Reldan, Safrotin, Acetellic, DDVP, Antrix) demonstrate the utility of this method for detecting subtle perturbations of the CNS and neuromuscular system.</jats:p

Stress tolerance in a polyextremophile: the southernmost insect

Since biotic interactions within the simple terrestrial communities on the Antarctic Peninsula are limited compared with tropical and temperate regions, survival is largely dictated by the numerous abiotic challenges. Our research focuses on adaptations to environmental stresses experienced by the Antarctic midge (Belgica antarctica Jacobs, 1900), the southernmost free-living insect. Midge larvae can survive freezing and anoxia year-round. Not only can frozen larvae undergo rapid cold-hardening (RCH) at temperatures as low as –12 °C, but RCH develops more rapidly in frozen compared with supercooled larvae. Whether larvae overwinter in a frozen state or cryoprotectively dehydrated may depend on hydration levels within their hibernacula. Larvae constitutively up-regulate genes encoding heat shock proteins, as well as the antioxidant enzymes superoxide dismutase and catalase. Larvae accumulate osmoprotectants in response to freezing, desiccation, and exposure to seawater; exposure to one of these osmotic stressors confers cross-tolerance to the others. Molecular responses to dehydration stress include extensive genome-wide changes that include differential expression of aquaporins among tissues, upregulation of pathways associated with autophagy, inhibition of apoptosis, and downregulation of metabolism and ATP production. </jats:p