Light-evoked walking in crayfish: Behavioral and neuronal responses triggered by the caudal photoreceptor

Abstract

The caudal photoreceptors (CPRs) of crayfish (Procambarus clarkii) can trigger walking and abdominal movements by their response to light.1. In a restrained, inverted crayfish, illumination of A6 evoked a CPR discharge followed by leg movements and bursting from the abdominal tonic flexor (TF) motoneurons. Intracellular electrical stimulation of a single CPR at high frequency (80 Hz) evoked similar responses.2. Responses only occurred when a single CPR axon was driven at 60 Hz or more and outlasted the stimulus.3. CPR stimulation also excites the pattern-initiating network (Moore and Larimer 1987) in the abdomen.4. The axon of the CPR projects from ganglion A6 to the brain. Terminal branches occur in the subesophageal ganglion and the brain. A small descending interneuron is dye-coupled to CPR in the subesophageal ganglion.5. In animals with cut circumesophageal connectives, the CPRs can evoke walking and the abdominal motor pattern.6. The relationship of the abdominal motor pattern to walking is altered by restraint and/or inversion. In freely moving crayfish, the cyclic abdominal motor pattern is only observed with backward walking. In restrained, inverted crayfish, the motor pattern occurs with both forward or backward walking.

Photosensitivity of the Central Nervous System of Limulus polyphemus

“…Photoresponses in the segmental nerves have been reported in the crayfish and the swallowtail butterfly. In the crayfish, illumination of the terminal abdominal ganglion evokes a cyclic firing pattern from the abdominal tonic flexor motor neurons, as recorded from the nerve roots (Edwards, 1984;Simon and Edwards, 1990). Spontaneous discharges were recorded in the dark from the sixth peripheral nerve of the terminal abdominal ganglion of the butterfly, and the frequency of some impulses was enhanced or inhibited upon direct illumination of the ganglion (Arikawa et al ., 1991).…”

Circadian clocks in crustaceans: identified neuronal and cellular systems

“…The CPR neurons depolarise upon photic stimulation of the ganglion, but do not adapt over time (291,292). The neuroanatomy of these cells has been detailed to some extent (291,(293)(294)(295), but full morphological details such as final projection sites and terminal connectivities have not been fully resolved. Some additional interneurons located in more anterior abdominal ganglia have been described as photosensitive, but their neuroanatomy and physiological functions are not understood (291).…”

“…2000 lux for 10-30min), the CPR initiates phase shifts in locomotory (296,303) and ERG rhythms (84,298). In the cases of its effects on the ERG and the size of the pseudopupil (87), the CPR most likely feeds sensory information into more anteriorly located pacemaker systems via the ascending projections running through the entire VNC into the brain (293), although the postsynaptic interneuronal targets have not been identified (12).…”

Chronic electromyographic analysis of circadian locomotor activity in crayfish

“…In addition, the previous studies demonstrated that the caudal photoreceptor of crayfish could trigger walking by their response to light stimulation [60][61][62]. In our experiments under the LD condition (Fig.…”