Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...
Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...
Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
General Introduction 5<br />
Figure 1.1: Structure <strong>of</strong> a s<strong>in</strong>gle <strong>in</strong>sect olfactory sensillum (adapted and modified<br />
from Vogt (1987)). Odorants enter the sensillum lymph through pores <strong>in</strong> the cuticular<br />
wall and <strong>in</strong>teract with the b<strong>in</strong>d<strong>in</strong>g prote<strong>in</strong>s present <strong>in</strong> the lymph which confer them<br />
onto the odorant receptors present on the dendritic membrane <strong>of</strong> the bipolar olfactory<br />
receptor neuron. Degrad<strong>in</strong>g enzymes present <strong>in</strong> the sensillum lymph may help <strong>in</strong> the<br />
clear<strong>in</strong>g <strong>of</strong> odorants from the lymph.<br />
The sensillum types present on moth antennae can be classified <strong>in</strong>to six different<br />
groups. These are the sensilla trichodea, sensilla basiconica, sensilla auricillica,<br />
sensilla chaetica, sensilla styloconica and sensilla coeloconica. Sensilla trichodea are<br />
very long, th<strong>in</strong>, porous hair-like structures with sharp po<strong>in</strong>ted tips (Schneider, 1964).<br />
Unbranched dendrites <strong>of</strong> up to three neurons <strong>in</strong>nervate this sensilla type (Keil, 1999).<br />
They are present <strong>in</strong> high numbers <strong>in</strong> male moths, while they occur <strong>in</strong> low numbers or<br />
not at all <strong>in</strong> female moths and thus were implicated to be <strong>in</strong>volved <strong>in</strong> recognition <strong>of</strong><br />
sex pheromone components released by female moths (Seabrook, 1978). The specific<br />
tun<strong>in</strong>g <strong>of</strong> this sensilla type to sex pheromones was confirmed by s<strong>in</strong>gle sensillum<br />
electroantennogram (EAG) record<strong>in</strong>gs (Shields and Hildebrand, 2001). The females<br />
<strong>of</strong> some moth species also carry large numbers <strong>of</strong> this sensilla type, however, these<br />
are shorter and the neurons are responsive to general odorants (Nagy and George,<br />
1981). Sensilla basiconica are shorter with blunt rounded tips and are <strong>in</strong>nervated by<br />
the dendrites <strong>of</strong> up to 50 neurons (Schneider, 1964). This sensilla type has been<br />
implicated <strong>in</strong> the detection <strong>of</strong> plant volatiles <strong>in</strong> S. littoralis (Anderson et al., 1995) and