A comparative study of antennal mechanosensors in insects

Abstract

Like morphological traits, neural circuits and their behavioural output also undergo evolutionary modification. However, because these traits do not survive fossilization, it is necessary to adopt a comparative approach to study how evolutionary modifications in the neuromuscular apparatus influence behavioural evolution. In recent times, this approach has shown much promise in helping understand how organismal behaviour evolves with the underlying sensorimotor components. As a case in point, we investigate how the antennal mechanosensors and their central projection patterns have diversified in different insect orders. Specifically, we survey the structure and neural arborization patterns of the mechanosensory Böhm’s bristles, located at the base of the insect antennae, which sense the coarser movements of the antennae. We also compare the Johnston’s organs which are located in the pedicel-flagellar joint of the antennae and which sense finer, passive movements of the flagella. Our investigations show that the broad patterns of neural arborization in the brain are conserved, even though the morphological characteristics of both the antennae and the brain are quite diverse across insects. This suggests that the antennal positioning behaviours in insects, and the underlying mechanosensory projection patterns, are highly conserved despite the vast differences in their antennal morphology.