Recordings of activity of the rock lobster dactyl sensory nerve during walking on a driven belt showed that the receptors of this nerve were mainly active during the power stroke when the leg was loaded. This nerve contains in particular the afferent fibres of the funnel canal organ (FCO) which are bimodal sensillae located in the cuticle of the dactylopodite of crustacean walking legs.
In the standing animal, brief electrical stimulation of the dactyl nerve had an influence on the proximal leg muscles of the stimulated leg. The promotor and levator muscles were excited and the remotor and depressor muscles were inhibited.
The opposite reaction was observed in adjacent ipsilateral legs in response to stimulation of a middle leg: the promotor and levator were inhibited and the remotor and depressor excited.
The resulting movement by the stimulated leg was stereotyped and always consisted of a lift-off from the substratum and a slight shift in the forward direction. The response in the adjacent legs was not powerful enough to elicit a movement.
In the walking animal the response of a single leg was dependent on the phase at which a stimulus arrived during the step cycle: during a power stroke (PS) this cycle was interrupted and a return stroke (RS) was initiated and continued. A stimulation at the normal switch from PS to RS had little effect, whereas a stimulation at late RS very often delayed the start of the following PS. Opposite reactions were given by the adjacent unstimulated legs: an RS was interrupted and a PS initiated or prolonged by the stimulus.
A comparison between ipsilateral walking legs showed the existence of some obvious differences: legs 4 and 5 were able to reset the walking pattern of all the legs, whereas the more anterior leg 3 returned to its old trajectory after stimulation and thus had no influence on the other legs.
Dactyl Sensory Influences on Rock Lobster Locomotion: I. Intrasegmental and Intersegmental leg Reflexes During Standing and Walking
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U. W. E. MÜLLER, FRANÇOIS CLARAC; Dactyl Sensory Influences on Rock Lobster Locomotion: I. Intrasegmental and Intersegmental leg Reflexes During Standing and Walking. J Exp Biol 1 January 1990; 148 (1): 89–112. doi: https://doi.org/10.1242/jeb.148.1.89
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