[Biochemical manifestations of the poisoning of larvae of Aedes aegypti (Insecta, Diptera) by the delta-endotoxin of Bacillus thuringiensis israelensis. I. Hemolymph carbohydrates].

The glycemia of 4th instar larvae of Aedes aegypti (Diptera Culicidae) was determined over a 30 min to 36 hrs period following their immersion in water containing 0.00-0.01-0.02-0.1-1.0 mg per liter of a 12,000 I. U. per mg preparation of the delta-endotoxin of Bacillus thuringiensis israelensis. Seven major carbohydrate fractions were separated in the haemolymph, among which glycogen, trehalose and glucose were identified; the most concentrated of the 4 remaining unknown fractions, exhibits a similar chromatographic behavior but different chemical properties than glucuronic acid. The glycogen fraction shows two large amplitude peaks at 1 hr 30 and 6 hrs with 0.1 mg/l, whereas with the 2 lower doses (0.01 and 0.02 mg/l) a first drop from 30 min to 1 hr is followed by a peaking at 12 hrs. The haemolymph trehalose concentrations of intoxicated larvae increase relatively to controls 2 hrs after incubation with the lower dose; by contrast, they decrease with the 2 higher doses. The glucosemia increases in all cases, but more markedly with the higher dose as soon as 1 hr following the treatment. A positive correlation was found over the whole treatment duration between the glucosemia nd the trehalosemia of control larvae. The regression slope of this relationship decreases with increasing toxin doses and turns to negative values with 0.1 and 1.0 mg/l. These observations suggest the hypothesis that a uncontrolled increase of trehalase activity develops according to the increasing stages of intoxication. This clearly differenciates the effects of the B. T. i toxin from those of parasites, such as Fungi, Sporozoans or Nematodes in Mosquitoes.