The effect of temperature on infection, development and reproduction of heterorhabditids.

The effect of temperature on infection, development and reproduction of five Heterorhabditis isolates was examined in Galleria mellonella larvae. Infectivity was examined at six temperatures (5, 10, 15, 20, 25 and 30 degrees C). The proportion of Galleria infected remained relatively constant, only dropping at extremes of the temperature range tested. However, the mean number of nematodes per host produced a different trend, with each isolate displaying optimal infectivity at 25 degrees C. The temperature range over which the juveniles could infect differed between the isolates. This is thought to be related to the geographic origins of the species. Development and reproduction occurred over a slightly narrower temperature range than that allowing infection to occur. Differences between the isolates at which development and reproduction occurred were noted. There were also differences in the mean number of juveniles produced per cadaver following either infection in sand (10 nematodes/larva) or the injection of one juvenile per larva, suggesting that reproduction is tightly regulated by density-dependent constraints.