The Role of the Peripheral Environment of Neuronal Receptors in Stimuli Perception by Insects’ Sense Organs: Facts and Hypotheses

Abstract

The role of intermediate substrates represented by morphological structures or chemical compounds located between the information carrier (stimulus) and the dendrite receptor membrane of insect sense organs is considered an example of olfactory, visual, mechanical, hygro-, and thermoreceptors. Intermediate substrates in olfactory sensillae are represented by their cuticular regions, pores or pore-tubular system, sensillum lymph, and pheromone-binding proteins. Intermediate structures also imply articular membrane (mechanoreceptor hairs), tympanic membrane (hearing organs), mineral statoliths (gravity receptors), iron oxide nanoparticles (magnetic field receptors), matrix surrounding the dendrites (hygroreceptors), microparticles associated with the dendrite membrane (thermoreceptors), and nonsclerotized mesocuticle (infrared receptors). There are two stages in propagation of a signal that is perceived by sense organs of most modalities: (1) before a signal contacts the peripheral environment (substance or structure) and (2) after a signal contacts the peripheral environment. Besides, a signal of one modality on the first stage of its propagation can be replaced by a signal of another modality at the second stage of propagation, as, for example, in hygro- or thermoreceptors, since the primary stimulus (moisture, heat/cold, or infrared radiation) is replaced by a mechanical effect on the dendrite membrane of its peripheral environment. The mechanisms of signal modality substitution in many sense organs, as well as the role of odorant-binding proteins and pore tubules in olfactory sensillae, have not been fully elucidated and require further investigation.