Response of cruiser and ambusher entomopathogenic nematodes (Steinernematidae) to host volatile cues

Abstract

Two species of entomopathogenic nematodes, an ambush forager (Steinernema carpocapsae) and a cruising forager (S. glaseri), were assayed for their responses to volatiles associated with Galleria mellonella (Insecta: Lepidoptera). The responses of entomopathogenic nematodes to six host-associated volatile treatments were assayed. Live G. mellonella, live G. mellonella with the cuticular hydrocarbons removed, live G. mellonella with carbon dioxide removed, dead G. mellonella, dead G. mellonella with the cuticular hydrocarbons removed, and volatiles from S. exiqua feces were assayed in a Y-tube choice aparatus. Steinernema glaseri were attracted only to treatments producing carbon dioxide. Steinernema carpocapsae showed no significant response to any treatments tested. To assess the directionality of the response toward live G. mellonella, net average movement per nematode after 5, 10, and 20 min was measured for both nematode species. The assay method was based on the "quadrant plate" bioassay, with a 9 cm Petri dish containing 2% agar. Steinernema carpocapsae showed little directionality of response, whereas S. glaseri was attracted to carbon dioxide. We conclude that carbon dioxide attracts S. glaseri to areas likely to hold hosts. Ambush foragers are less influenced by cues associated with hosts or their habitat.

Movement of Heterorhabditis amazonensis and Steinernema arenarium in search of corn fall armyworm larvae in artificial conditions

“…The infective juveniles can use environmental cues to locate the host. Some of these stimuli are the concentration of CO 2 in the environment (Gaugler et al, 1980;Lewis et al, 1993;Lewis, 2002), the vibration caused by the host in the substrate (Torr et al, 2004), temperature gradients (Burman and Pye, 1980;Byers and Poinar Jr., 1982), the presence of an electric current (Shapiro-Ilan et al, 2009), and the presence of chemical compounds (Pye and Burman, 1981;Shapiro et al, 2000) such as the contents of the digestive tract of the insect (Grewal et al, 1997) and its excretion products (Schmidt and All, 1979;Grewal et al, 1993). The presence of these factors increases the chance of infective juveniles to find the host.…”

Simulated roots and host feeding enhance infection of subterranean insects by the entomopathogenic nematode Steinernema carpocapsae

“…strate ambush foragers like S. carpocapsae exhibit ranging search (Lewis et al, 1993); tree roots or the twig used as a routeway here may provide a surface that would encourage ranging in the IJs. Soil composition and texture strongly influence EPN dispersal and infectivity (Georgis and Poinar, 1983;Koppenhöfer and Fuzy, 2006), so the fact that the medium (sand or sand/peat mix) had no effect on nematode success supports the assumption that IJs are mainly moving along the twig rather than through the medium.…”

“…In the pine weevil field trials, nematodes applied at soil level around tree stumps parasitised weevils feeding under the bark of tree roots up to 50 cm below the soil surface. While rather few S. carpocapsae IJs penetrate deep into soil (Georgis and Poinar, 1983), on an agar substrate ambush foragers like S. carpocapsae exhibit ranging search (Lewis et al, 1993). We hypothesise that roots of trees or other plants may provide a physical routeway, encouraging penetration by ambush foragers deep into soil.…”

Behavioral ecology of entomopathogenic nematodes

“…Lewis et al (1993) found that Steinernema glaseri (Steiner) responded positively to volatile cues from an insect host and that this response was eliminated if CO 2 was removed. Grewal et al (1994) found a similar level of response to volatile cues for other cruise foraging entomopathogenic nematode species in Steinernema and for two species of Heterorhabditis.…”