Jackson Estuarine Laboratory


The effects of water pressure, temperature, and current cycles on circatidal rhythms expressed by the American horseshoe crab, Limulus polyphemus


The American horseshoe crab, Limulus polyphemus, expresses tidal rhythms of locomotion that can be entrained to cyclic fluctuations in water depth, but the ability of other tidal cues to entrain locomotor activity has not been assessed. In this study, tidal inundation cycles of ∼12.4 h delivered in the laboratory clearly entrained the locomotor patterns of most animals. However, smaller amplitude water level fluctuations and large amplitude temperature cycles (10°C) were less successful while small-amplitude temperature fluctuations (3°C) and current cycles (0.3 m s−1) were unsuccessful. In the field, animals confined to modified running wheels expressed rhythms of locomotor activity that were clearly synchronized with the tides, but only if they were allowed to experience water level changes. Overall, these results suggest a hierarchy among potential tidal entrainment cues: inundation and water level changes are of primary importance, while other factors such as current and temperature changes appear to play secondary roles.


Jackson Estuarine Laboratory, Biological Sciences

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Marine and Freshwater Behaviour and Physiology


Taylor & Francis

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