Rhythms of Locomotion Expressed by Limulus polyphemus, the American Horseshoe Crab: II. Relationship to Circadian Rhythms of Visual Sensitivity

In the laboratory, horseshoe crabs express a circadian rhythm of visual sensitivity as well as daily and circatidal rhythms of locomotion. The major goal of this investigation was to determine whether the circadian clock underlying changes in visual sensitivity also modulates locomotion. To address...

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Bibliographic Details
Published in:The Biological bulletin (Lancaster) 2008-08, Vol.215 (1), p.46-56
Main Authors: Watson, Winsor H., Bedford, Lisa, Chabot, Christopher C.
Format: Article
Language:English
Subjects:
Animal behavior
Animals
Biological Clocks
Circadian Rhythm
Circadian rhythms
Crabs
Crustaceans
Decapoda
Electrodes
Electroretinography
Estuaries
Eyes
Horseshoe crabs
Horseshoe Crabs - physiology
Limulus polyphemus
Locomotion
Marine
Neurobiology and Behavior
Photoperiod
Physiological aspects
Sea water
Sensory memory
Vision, Ocular
Water
Water depth
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Summary:In the laboratory, horseshoe crabs express a circadian rhythm of visual sensitivity as well as daily and circatidal rhythms of locomotion. The major goal of this investigation was to determine whether the circadian clock underlying changes in visual sensitivity also modulates locomotion. To address this question, we developed a method for simultaneously recording changes in visual sensitivity and locomotion. Although every animal (24) expressed consistent circadian rhythms of visual sensitivity, rhythms of locomotion were more variable: 44% expressed a tidal rhythm, 28% were most active at night, and the rest lacked statistically significant rhythms. When exposed to artificial tides, 8 of 16 animals expressed circatidal rhythms of locomotion that continued after tidal cycles were stopped. However, rhythms of visual sensitivity remained stable and showed no tendency to be influenced by the imposed tides or locomotor activity. These results indicate that horseshoe crabs possess at least two biological clocks: one circadian clock primarily used for modulating visual sensitivity, and one or more clocks that control patterns of locomotion. This arrangement allows horseshoe crabs to see quite well while mating during both daytime and nighttime high tides.
ISSN:0006-3185
1939-8697
DOI:10.2307/25470682