Light and temperature entrainment of a locomotor rhythm in honeybees |
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Authors: | DARRELL MOORE MARY ANN RANKIN |
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Affiliation: | Department of Biological Sciences, East Tennessee State University, Johnson City, Tennessee, and *Department of Zoology, University of Texas, Austin, Texas, U.S.A. |
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Abstract: | Abstract. The circadian locomotor (walking) rhythms of forager honeybees (Apis mellifera ligustica L.) were entrained to eight different 24 h light-dark cycles. The phases of activity onset, peak activity, and offset were correlated with the lights-off transition, suggesting lights-off as the primary zeitgeber for the rhythm. Further support for this hypothesis was provided by LD 1:23 experiments, in which entrainment occurred when the light pulse was situated at the end, but not at the beginning, of the subjective photophase. Steady-state entrainment of the locomotor rhythm was achieved with square-wave temperature cycles of 10oC amplitude under constant dark: most of the activity occurred within the early thermophase. Smaller amplitude temperature cycles yielded relative coordination of the rhythm. Interactions of temperature and light-dark cycles resulted in entrainment patterns different from those elicited in response to either cycle alone or those formed by a simple combination of the two separate responses. Furthermore, temperature cycles having amplitudes insufficient for entrainment of the rhythm nevertheless modified the pattern of entrainment to light - dark cycles, suggesting a synergism of light and temperature effects on the underlying circadian clock system. |
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Keywords: | Apis mellifera honeybee foragers circadian rhythm locomotor behaviour entrainment light–dark cycles temperature cycles. |
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