Behavioral Responses of Meloidogyne incognita to Small Temperature Changes

Small, rapid temperature changes were generated by incandescent radiation, and behavioral responses of Meloidogyne incognita juveniles were recorded with high time resolution by computer tracking. Temperature changes away from the preferred temperature resulted in decreases in the rate of movement and increases in the rate of change of direction, whether the changes were toward warmer or cooler temperatures. These behavioral changes lasted about 30 seconds. Temperature changes toward the preferred temperature caused the response rates to change in the opposite directions, and the behavioral changes persisted for several minutes. These results demonstrate that nematodes can respond to a purely temporal thermal stimulus in a manner consistent with efficient indirect orientation or klinokinesis. The rate of temperature change was estimated to be of the order of 10 C/second, suggesting that the nematodes detected a change of about 0.001 C.