Active touch in orthopteroid insects:behaviours, multisensory substrates andevolution

摘要

Orthopteroid insects (cockroaches, crickets, locusts and related species) allow examination of activesensory processing in a comparative framework. Some orthopteroids possess long, mobile antennaeendowed with many chemo- and mechanoreceptors. When the antennae are touched, an animal’sresponse depends upon the identity of the stimulus. For example, contact with a predator may leadto escape, but contact with a conspecific may usually not. Active touch of an approaching objectinfluences the likelihood that a discrimination of identity will be made. Using cockroaches, wehave identified specific descending mechanosensory interneurons that trigger antennal-mediatedescape. Crucial sensory input to these cells comes from chordotonal rgans within the antennalbase. However, information from other receptors on the base or the long antennal flagellumallows active touch to modulate escape probability based on stimulus identity. This is conveyed,at least to some extent, by textural information. Guidance of the antennae in active explorationdepends on visual information. Some of the visual interneurons and the motor neurons necessaryfor visuomotor control have been identified. Comparisons across Orthoptera suggest an evolutionary model where subtle changes in the architecture of interneurons, and of sensorimotor controlloops, may explain differing levels of vision–touch interaction in the active guidance of behaviour.