Summary
The eye of the frilled sea hare,Bursatella leachi plei, expresses a circadian rhythm in the frequency of spontaneously occurring optic nerve impulses. The rhythm will free-run for at least 3 cycles in vitro (Fig. 2) and can be entrained by light cycles provided in vivo (Fig. 4 A). While bothBursatella andAplysia eyes contain circadian pacemakers the two rhythms differ in several respects: (1) the peak impulse frequency forBursatella eyes is only 96/h (±36 SD) compared with 247/h (±61 SD) forAplysia. (2) The ocular waveform of theBursatella rhythm exhibits a steep rise and fall from peak frequencies and lacks the delayed falling phase which creates a ‘shoulder’ on the ocular waveform inAplysia (Fig. 2). (3) The in vitro free-running period of theBursatella ocular rhythm is 21.2 h (±0.6 SD) compared with 24.3 h (±0.9 SD) for theAplysia rhythm (Fig. 2). (4) The steady state phase angle for entrainment differs withBursatella eyes showing a median activity peak at +3 Z.T. compared with a medianAplysia peak at −1 Z.T. (Fig. 4).
We also investigated the locomotor rhythm.Bursatella were found to be predominantly diurnal when exposed to L∶D, 12∶12 (Fig. 5A) and to exhibit anticipatory locomotor activity when maintained on L∶D), 9∶15 (Fig. 6). The eyes appear to play a minor role, if any, in timing the locomotor rhythm. EyelessBursatella remained diurnal on L∶D, 9∶15 and most animals continued to exhibit anticipatory behavior (Fig. 6). These results suggest that theBursatella eye plays a less prominent role than theAplysia eye in controlling locomotor behavior.
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Abbreviations
- D∶D :
-
constant darkness
- L∶D :
-
12∶12 24 h light cycles 12 h light, 12 h dark
- EST :
-
Eastern Standard Time
- Z.T. :
-
Zeitgeber Time
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We would like to thank L. Baird, W. Kilmartin and S. Wallace for help with animal maintenance, data presentation and photography. We also thank T. Breeden for our computer programs. This work was supported by NIH grant NS-15264 to G. Block.
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Block, G.D., Roberts, M.H. Crcadian pacemaker in theBursatella eye: Properties of the rhythm and its effect on locomotor behavior. J. Comp. Physiol. 142, 403–410 (1981). https://doi.org/10.1007/BF00605452
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DOI: https://doi.org/10.1007/BF00605452