Different seasonal rearing conditions do not affect pheromone-sensitive receptor neurons of the adult cabbage looper moth, Trichoplusia ni

In southern parts of the United States the cabbage looper moth, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), is multivoltine, and therefore successive generations experience different environmental conditions during development from larvae to adults. Since environmental conditions are thought to influence pheromone communication, we tested the effects of two different temperature and light regimes (selected to mimic those occurring in the spring and summer growing seasons in the south) during rearing on the response characteristics of the adult male olfactory receptor neurons responsible for detecting the major component of the female pheromone. The dose-response functions of receptor neurons from the warm- and cold-reared insects were similar in both their slopes and thresholds to stimulation with the major component of the female-emitted pheromone, (Z)-7,dodecen-1-ol acetate and (Z)-7,dodecen-1-ol, a behavioural inhibitor. In double pulse experiments, designed to emulate the temporal dispersion of pheromone in nature, neurons were stimulated with short pulses (200ms) of (Z)-7,dodecen-1-ol acetate separated by varying intervals. Intervals as short as 30 ms reduced the response to a second pulse by over 50%. When the intervals between pulses were longer than 2 s, significant differences were not seen between the responses to the first and to the second pulse. These temporal response patterns were similar in both warm- and cold-reared animals.