The effect of insecticide treatment and injection of sodium chloride and sucrose solutions on the water-salt homeostasis of lepidopterous larvae

Abstract

AbstractThe osmolality and ion concentrations in the haemolymph and the body of lepidopterous larvae were studied under different experimental conditions. It was shown that the haemolymph osmolality of Aglais urticae (Linnaeus) larvae returned to normal three hours after the injection of 0.4 M sucrose or 0.4 M sodium chloride, despite the fact that in the latter case, the level of sodium was very high (to 53.1 mM vs 4.5 mM in control). The injection of 0.2 M or 0.4 M sodium chloride did not induce significant changes in the concentration of ions, other than sodium, in haemolymph. Treatment of Mamestra brassicae (Linnaeus) larvae with insecticides (DDVP, lindane, decis) led to a fast loss of body weight (up to 30%). This was due to dehydration, which was accompanied by a significant decrease of potassium content in body tissue, but not in the haemolymph. Study of the haemolymph parameters of Lepidoptera and insects taken from their natural environment indicates that the lowest values of variation coefficient related to osmolality and to the concentration of the dominant cation of the haemolymph (sodium, potassium or magnesium). These data suggest effective regulation of osmolality and ion concentration in the insect haemolymph.