The Role of the Caudal Photoreceptor in Crayfish

Anna-Marie KelemenScripps College

December 02, 2009© 2009 Auburn University

The Caudal PhotoreceptorTwo in the 6th abdominal

ganglionPhotosensitive[6]

Increase firing when exposed to light

Linked to crayfish mobility[3]

© 1990 Simon & Edwards

Previous research Whelsh (1934) –response to light

Theory: that CPR serves to warn of exposure of the tail to light and therefore to attack.

Kennedy (1958) – Theory: photoreceptors are slightly modified neurons with photosensitive elements

Uchizono (1962) – lamellar, honeycombed structures assumed to be photoreceptive elements in 6th ganglion neurons

Simon (1989) – CPRs are trigger neurons for locomotor behavior Can choose the motion of response (Ex. forward

vs. backward walking)

Kendall Snyder (2009) Used LED to imitate light on 6th ganglion

Light increased locomotion showing linkage to CPR

© 1962 Uchizono

Locomotor Activity

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Figure 1. Single movement sample, crayfish 3. (a) No light onset. (b) Light onset after 30 seconds of recording. Dotted lines indicate time during which no movement may occur for trial to be counted..

Light activation of CPR results in locomotor behavior of crayfish

© 2009 Kendall Snyder

Response to Light80

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© 2009 Karin Westin

Hypothesis

To show that the increase in locomotor activity in the crayfish is due to the illumination of the CPR. Show the relationship between muscle activity

in relation to the 6th ganglion and illumination.

DissectionCrayfish is sedated in ice bath for

10 minutesDissection scissors used to cut off

tail Tail is pinned to a dissection dish

Swimmerets removedRemove all connective tissue

Separate out nerve cord

Nerve cord pinned to dissecting dish and soaked in saline

Fine forceps were used to desheath the cord, removing connective tissues

Ganglia exposed

© 2008 Smith College

© 2008 Smith College

Methods and MaterialsGoal #1To develop a new

technique in which I can precisely read the responses of the CPR to light

Use a suction electrode to locate the CPR in the 6th ganglionAccurately measure

activity with and without light

Methods and MaterialsGoal #2

To carry out a semi-intact preparation in which the animal is still alive

Relationship between activation and movement through direct observation

Crayfish displayed on back with ventral side facing upwards

Constantly sedated with coldFine silver wires twisted together

and inserted into the muscles at the base of a walking legMultiple muscles to see correlation

between muscle activity and CPR firing

Methods and MaterialsGoal #3

Assuming first two goals successfulKnockout neurons and observe

electrical behaviorSedate crayfish and open abdomen

Sever nerve chord between the 5th and 6th ganglia Use suction electrode to measure

activity

Tells us whether any source of increase in muscle activity was actually caused by activity in the 6th ganglion

AcknowledgementsI would like to thank Professor Copp for

reviewing this presentation and for the encouragement and advice throughout this experiment.

I would also like to thank Karin Westin for teaching me the dissection technique necessary for this experiment. I would also like to thank her for providing me with her past research so as to further my understanding and knowledge of the material.

Literature Cited1) Kennedy, D. & Preston, J.B. “Activity pattern of interneurons in the caudal

ganglion of the crayfish.” 1960. The Journal of General Physiology. 43 (3): 655-670

2) Prosser, Ladd. “Action potentials in the nervous system of the crayfish.” 1935. The Journal of General Physiology. 19 (1): 65-73.

3) Simon, Ted W. “Light-evoked walking in crayfish: Behavioral and neuronal responses triggered by the caudal photoreceptor.” 1989. The Journal of Comparative Physiology. 166: 745-755.

4) Snyder, Kendall. “Light activation of the caudal photoreceptors: effects on locomotor behavior in Procambarus clarkii.” 2009. Senior Thesis in Neuroscience. 1-30.

5) Uchizono, Koji. “The structure of possible photoreceptive elements in the sixth abdominal ganglion of the crayfish.” 1962. Brief Notes. 15 (1): 151-154.

6) Whelsh, John H. “The caudal photoreceptor and responses of the crayfish to light.” 1934. Journal of Cellular and Comparative Physiology. 04 (3): 379-388.

7) Yano, Takeshi; Ibusuki, Shoichiro; and Takasaki, Mayumi. “A comparison of intracellular lidocaine and bupivacaine concentrations producing nerve conduction block in the giant axon of crayfish In Vitro.” 2006. Anesthesia & Analgesia. 102 (06):1734-1738.

8) (2005, February 08). Worms and fish feel no pain. Cape Times, 2005: 001.