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Photoperiodic effects on activity behaviour in the spiny eel (Macrognathus pancalus)
Indian Journal of Experimental Biology
|May 24, 2014
Summary
Spiny eels exhibit nocturnal behavior, with their circadian locomotor activity synchronized by light-dark cycles. Constant light conditions disrupt this rhythm, with intensity influencing the degree of disruption.
Area of Science:
- Chronobiology
- Animal Behavior
- Fish Physiology
Background:
- Circadian rhythms govern daily physiological and behavioral patterns in many organisms.
- Photoperiod significantly influences the circadian systems of various species, including fish.
- The spiny eel (M. pancalus) is a species whose circadian locomotor activity patterns require further investigation.
Purpose of the Study:
- To characterize the circadian locomotor activity of the spiny eel (M. pancalus) under varying photoperiodic conditions.
- To determine the effect of light intensity on circadian rhythmicity in spiny eels.
- To assess the impact of altered night lengths on the locomotor activity patterns of spiny eels.
Main Methods:
- Two experiments were conducted on spiny eels housed individually.
- Experiment 1: Fish were exposed to 12-hour light:12-hour dark cycles, then constant conditions of darkness (DD), dim light (LL-dim), or bright light (LL-bright).
- Experiment 2: Fish were exposed to sequential decreasing night lengths (increasing photoperiods) before release into constant darkness. Locomotor activity was continuously recorded using infrared sensors.
Main Results:
- Spiny eels demonstrated predominantly nocturnal activity (>90%) under entrained conditions.
- Under constant conditions, a significant proportion of fish exhibited free-running circadian activity with periods varying based on light intensity.
- Decreasing night length (increasing photoperiod) influenced both the amplitude and duration of locomotor activity.
Conclusions:
- Spiny eels are nocturnal and possess a circadian system that can be synchronized to light-dark cycles.
- Locomotor activity in spiny eels is under circadian control and is influenced by photoperiod.
- High light intensity under constant conditions can disrupt circadian locomotor activity in spiny eels.
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