Effects of the antennal sensilla distribution pattern on the behavioral responses of Tribolium castaneum (Coleoptera: Tenebrionidae)
Keywords:
antenna, sensillum, scanning electron microscopy, transmission electron microscopy, behavior responseAbstract
The morphology and distribution of sensilla on the antennal flagella of male and female adults of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), were investigated by using scanning and transmission electron microscopy (SEM and TEM). Behavioral responses of male and female adults were measured with 12 host-plant and leaf-volatile stimuli. No sexual dimorphism was observed in the distribution and types of sensilla. Two types of sensilla, trichodea and basiconica, were observed on the antennae. Sensilla trichodea were distributed on all antennal segments but were most abundant on the last 3 segments. In contrast, sensilla basiconica were found exclusively on the last 3 segments of the antenna. TEM cross sections showed sensilla trichodea to have a thick cuticular wall and regular point-shaped pores around the cuticular wall. Sensilla basiconica possessed a thin wall and continuous pores and dendrites. The pores on the walls of the sensilla indicate that they play a role in sensing chemical stimuli and in olfactory functions. Female and male adults of T. castaneum showed broad overlap in their behavioral responses to various odors. Preference for some volatiles was noted, but after removal of the 3 terminal antennal segments, there was no significant preference for any compound that had been previously attractive to the beetles when tested with the complete antennae.
Resumen
Se investigaron la morfología y distribución de las sensilas en los flagelos de las antenas de los adultos machos y hembras de Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) por medio del uso de la microscopía electrónica de barrido y de transmisión (SEM y TEM). Las respuestas de comportamiento de los adultos machos y hembras se midieron con 12 diferentes estímulos de plantas hospederas y volátiles de las hojas. No se observó dimorfismo sexual en la distribución y las clases de sensilas. Se observaron dos clases de sensilas, trichodea y basiconica, en las antenas. Las sensilas trichodeas se distribuyeron en todos los segmentos de la antena, pero fueron más abundantes en los últimos 3 segmentos. En contraste, las sensilas basiconicas se encontraron exclusivamente en los 3 últimos segmentos de la antena. Las secciones transversales de TEM mostró que las sensilas trichodeas tienen una pared cuticular gruesa y poros en forma de puntos fijos alrededor de la pared cuticular. Las sensilas basiconicas poseía una pared delgada y los poros y dendritas continuas. Los poros en las paredes de las sensilas indican que ellos juegan un papel en la detección de estímulos químicos y en las funciones olfativas. Las hembras adultas y machos de T. castaneum mostraron amplia superposición en sus respuestas de comportamiento a diferentes olores. Se notó una preferencia para algunas sustancias volátiles, pero después de la eliminación de los 3 segmentos terminales de la antena, no hubo ninguna preferencia significativa por cualquier compuesto que previamente había sido atractivo para los escarabajos cuando fueron evaluados con las antenas completas.
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