CHARACTERIZATION AND BASIS OF ENHANCED HOST-FINDING IN A GENETICALLY IMPROVED STRAIN OF STEINERNEMA-CARPOCAPSAE

The host-finding response of a strain (G13) of the entomopathogenic nematode, Steinernema carpocapsae, selected for enhanced host-finding was compared with that of two wild-type strains (All and Foundation). The G13 strain showed a significant response to insect hosts up to a distance of 20 cm, compared to 3.5 cm in the wild types. Increasing the exposure period from 1 to 8 hr did not result in a corresponding increase in host-finding for any strain. G13 selection against the wax moth, Galleria mellonella, enhanced host-finding of other insect species as well, but equivalent enhancement was achieved only against the house cricket, Acheta domesticus. Host-finding by G13 infective juveniles was positively correlated with host carbon dioxide production. Removal of host carbon dioxide as a cue resulted in complete inhibition of chemotaxis in all three nematode strains. Our results indicate that the basis for enhanced host-finding in G-13 nematodes was selection for enhanced chemosensitivity to carbon dioxide. © 1991.