Ordinary glomeruli in the antennal lobe of male and female tortricid moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae) process sex pheromone and host-plant volatiles

Abstract

Couto et al., 2005). In moths, plant odour processing occurs mainly in the ordinary glomeruli (Christensen and Hildebrand, 2002; Christensen and White, 2000) and pheromone processing occurs in distinct glomeruli, the macroglomerular complex (MGC) (Anton and Homberg, 1999;Hansson et al., 1992 Accepted 18 October 2010 SUMMARY Both sexes of Grapholita molesta, a key pest of stone fruits, are able to detect host-plant volatiles and the sex pheromone emitted by females, and to modify their behaviour accordingly. How olfactory information is processed in the central nervous system is unknown. Intracellular recordings and stainings were used to characterize antennal lobe (AL) neuron responses to single pheromone components, a behaviourally active blend of five peach volatiles and a pear-fruit ester. AL neurons with different response patterns responded to pheromone components and plant volatiles. In males more neurons responded specifically to the main pheromone component than in females, whereas neurons responding to all three pheromone components were more abundant in females. Neurons responding to all three pheromone components often responded also to the tested plant volatiles in both sexes. Responses to all pheromone components were dose dependent in males and females, but dose-response relationships differed between neurons and tested pheromone components. Among the five AL projection neurons identified neuroanatomically in males, no arborizations were observed in the enlarged cumulus (Cu), although all of them responded to pheromone compounds. In one of two stained projection neurons in females, however, the glomerulus, which is thought to be homologous to the Cu, was targeted. The processing of pheromone information by ordinary glomeruli rather than by the macroglomerular complex is thus a striking feature of this species, indicating that pheromone and plant volatile processing are not entirely separate in this tortricid moth AL. However, the absence of recorded pheromone responses in the Cu needs to be confirmed. Supplementary material available online at

Plant odour stimuli reshape pheromonal representation in neurons of the antennal lobe macroglomerular complex of a male moth

“…Excitatory responses of MGC PNs to plant odours have also been reported for S. littoralis (Anton and Hansson, 1995), and inhibitory responses of MGC PNs to plant odours were described in M. sexta (Reisenman et al, 2008). Similar evidence has been found in the tortricid moths Cydia pomonella and Cydia molesta, where responses to plant odours were found in MGC neurons and pheromone responses in PNs within other glomeruli (Trona et al, 2010;Varela et al, 2011b). Such results are in agreement with data from vertebrates, where both 'common' odours and pheromones can activate the main olfactory bulb and the accessory olfactory bulb (Xu et al, 2005), and thus overlapping processing of both odour types occurs in both compartments of the primary olfactory centre.…”

Reduced Mating Success of Female Tortricid Moths Following Intense Pheromone Auto-Exposure Varies with Sophistication of Mating System

“…Therefore, any sensory cross-adaptation would need to be broad. Crossadaptation of neurons to odor stimuli has been shown in numerous studies, indicating that processing of different odor stimuli may share common physiological pathways (Daniel et al, 1994;Takeuchi et al, 2003;Gottfried et al, 2006;Anton et al, 2011). Trona et al (2010 recently showed that structurally different sex pheromone and plant odor compounds interact in C. pomonella via an across-fiber coding pattern, with perception of these distinct chemicals relayed through projection neurons from ordinary glomeruli and from the macroglomerular complex.…”

Differential Interactions of Sex Pheromone and Plant Odour in the Olfactory Pathway of a Male Moth

“…As for vertebrates, the coding of these two types of odour cues was generally believed to occur in two separate pathways of the insect olfactory system. However, unusual representations of plant odours and pheromones were recently observed in tortricid moths: in Grapholita molesta , pheromone processing seems to occur in OG rather than in the MGC [23] and in Cydia pomonella there is no clear segregation between the pheromone and the general odour sub-systems in the AL, both odour classes being represented in both the MGC and in OG [24].…”