Physiological characterization of antennular flicking reflexes in the crayfish |
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Authors: | DeForest Mellon Jr |
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Institution: | (1) Department of Biology, Gilmer Hall, University of Virginia, Charlottesville, VA 22903, USA e-mail: dm6d@virginia.edu, US |
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Abstract: | The cellular substrates of antennular flicking behavior in the crayfish Procambarus clarkii were investigated. Flicking involves fast downward movements of the external filament of each biramous antennule (1st antenna),
and is mediated by phasic contractions of a short muscle, the external filament depressor. Phasic contractions of the external
filament depressor depend upon stereotyped impulse bursts in a single motorneuron (P1). These bursts have a characteristic
impulse frequency profile that is consistent upon successive occurrences. The temporal characteristics of the impulse burst
suggest that the central depolarizations generating each burst may be similar to driver potentials described for motor neurons
in crustacean cardiac ganglia. Responses of the external filament to odorants have a long latency and are characterized by
repetitive bursts and tonic activity in some external filament depressor fibers. Tonic activity in a slowly contracting muscle,
the antennular depressor muscle, is also evoked by chemical stimulation. Flicking is consistently evoked only by mechanical
or hydrodynamic stimulation of the cephalothorax, antennae and antennules. The sensitivity and short latency of the hydrodynamic
antennule-generated flick reflex is consistent with the sensitivity of rapidly conducting, hydrodynamically activated mechanoreceptor
neurons in both antennular filaments. I propose that antennular flicking, which has been shown to enhance the dynamic response
characteristics of olfactory receptor neurons on the external antennular filament, has evolved as a response to the turbulence
associated with fluid movement, within which chaotic odorant concentration fronts may be imbedded.
Accepted: 23 October 1996 |
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Keywords: | Crustacean Olfaction Impulse burst Electrophysiology Driver potentials |
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