LARVICIDAL ACTIVITY OF LECTINS ON LUCILIA-CUPRINA - MECHANISM OF ACTION

Larvae of the blowfly Lucilia cuprina (Wied.) (Diptera: Calliphoridae) were grown in vitro on a serum-free medium in the presence of a numbe r of lectins. Lectins with specificities for beta-(1,4)-N-acetylglucos amine (wheat germ lectin) and alpha-D-mannopyranosyl and (alpha-D-gluc opyranosyl residues (lentil lectin and Con A) caused strong concentrat ion-dependent inhibition of the growth of the larvae and substantial m ortality. Wheat germ lectin had the strongest effects, showing 50% inh ibition of larval growth at a concentration of 2 mu M and 100% mortali ty at 25 mu M. Other lectins with different sugar specificities had mu ch less effect. The mechanism of the larvicidal action(s) of wheat ger m lectin, lentil lectin and Con A was investigated. There were at leas t three effects of these lectins on L. cuprina larvae. First, these le ctins bound to and reduced the permeability of the peritrophic membran e of the larvae. Second, they reduced ingestion of diet medium by larv ae. Third, the lectins also bound to the apical membranes of larval gu t epithelial cells although there were no obvious signs of damage to t hese cells. It is concluded that the combination of these effects prob ably results in the starvation of the larvae. The implications of thes e results in terms of possible control strategies for L. cuprina are d iscussed.