Odour perception in the oriental fruit moth (=grapholita) molesta (busck)
- Autores: Nelia Antunes Tavares Varela
- Directores de la Tesis: Jesús Avilla Hernández (dir. tes.), César Gemeno Marín (codir. tes.)
- Lectura: En la Universitat de Lleida ( España ) en 2009
- Idioma: español
- Tribunal Calificador de la Tesis: María José Sarasúa Saucedo (presid.), Matilde Eizaguirre Altuna (secret.), Antonio De Cristofano (voc.), Alberto Ferrús Gamero (voc.), Christophe Gadenne (voc.)
- Materias:
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- Resumen
Chemical senses play a vital role throughout insect life, olfaction being the most important sense used to analyze the environment. Insect adult activity is largely guided by odours, emitted either by individuals of the same species or by other living organisms. Volatiles are detected by the insect antenna, in sensilla that house olfactory receptor neurons (ORNs) that detect and discriminate odour information. The ORNs send information to the antennal lobes (ALs), the primary integration centre for odour processing in the brain, which send it to higher brain centres for further analysis. The knowledge of volatiles that affect insect behaviour has permitted their use in pest control strategies, either as monitoring tools or as direct control measures (mating disruption, mass trapping, attract and kill, attract and sterilize). The Oriental Fruit Moth, Cydia (=Grapholita) molesta (Busck) (Lepidoptera: Tortricidae) is an important pest in fruit orchards with the adult activity largely guided by volatile odours and sensory cues and its control is mainly achieved by mating disruption. This thesis aimed to gain knowledge on C. molesta odour perception and processing using anatomical, physiological and behavioural studies.
As a first step in the study of olfactory processing in C. molesta, we investigated the anatomy of the central olfactory system with neuroanatomical and computational approaches. The AL glomeruli of both male and female adults were reconstructed and compared as to locate differences in size, location and shape. A three-dimensional (3D) map was obtained and distinct target areas of antennal and palpal receptor neurons were identified.
Intracellular recordings and staining techniques allowed the investigation of the electrophysiological properties of AL neurons and the identification of the targeted glomeruli. In both males and females the pheromone processing neurons were highly sensitive and different response patterns were observed. In males, only neurons arborising outside the male-specific macroglomerular complex were found to respond to pheromone, whereas a glomerulus close to the entrance of the antennal nerve housed branches of a pheromone responding neuron in a female.
To determine the behaviour of males, they were tested in the wind tunnel towards pheromone alone and in a sub-optimal dose in combination with host plant volatiles: three green leaf volatiles (GLV) - (Z)-3-hexenyl-1-yl acetate, (Z)-3-hexenol, and (E)-2-hexenal and two aromatics - benzaldehyde and benzonitrile. Generally, plant volatiles enhanced pheromone attractiveness, but only the blend of all five volatiles and pheromone elicited the higher attraction in the shortest time. Attraction was still high when GLV were taken from the blend but decreased when removing aromatics. When placed individually, (Z)-3-hexenol and benzonitrile presented high attraction. With the incorporation or removal of benzaldehyde, the lowest attraction was always observed nonetheless it were the only treatments where adult flight took less time.
Taken together, the results presented in this thesis provide new insights into central nervous odour integration and odour dependent behaviour of C. molesta. This work is a first step in the direction to fully understand C. molesta olfaction and will serve as a basis to investigate plasticity in odour-guided behaviour and its neuronal basis in this insect pest species.
Keywords: Cydia molesta, olfaction, antennal lobe, three-dimensional map, intracellular recording and staining, pheromone, plant volatiles.
