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The locomotory activity rhythm of the spiny mouse, A comys spinosissimus from southern A frica: light entrainment and endogenous circadian rhythms
Author(s) -
Hoole C.,
Oosthuizen M. K.,
Chimimba C. T.,
Bennett N. C.
Publication year - 2012
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.2012.00928.x
Subject(s) - circadian rhythm , entrainment (biomusicology) , darkness , rhythm , light cycle , biology , locomotor activity , medicine , endocrinology , endogeny , zoology , botany
The circadian rhythm of locomotor activity in the spiny mouse A comys spinosissimus from S outh A frica was investigated under controlled laboratory conditions. Nine individuals were subjected to six successive light cycles of approximately 2 weeks each as follows: (1) a standard light/dark (12:12 LD ) cycle; (2) a period of constant darkness ( DD ); (3) a second standard light/dark (12 L :12 D ) cycle; (4) an inverse of the LD (12:12 DL ) cycle; (5) a short day cycle (8:16 LD ); and (6) a long day cycle (16:8 LD ). All the animals exhibited entrainment of their activity to the LD and DL lighting regimes. Locomotor activity of A . spinosissimus occurred predominantly during the dark phases of the LD , DL , long day and short day cycles. Under LD , the mean percentage of activity was 88.7 ± 0.07% during the dark phase. When subjected to constant darkness, all animals expressed free‐running rhythms of locomotor activity (mean ± 1 standard deviation = 23.81 ± 0.33 h; range = 23.2–24.1 h). On the reverse LD cycle, the mean percentage of activity was 81.4 ± 0.09% during the dark phase of the cycle. Mice exhibited significantly more daytime activity during the long day cycle (20.3 ± 5.8%) and no significant change in dark phase activity during the short day cycle (90.1 ± 4.01). The spiny mouse possesses a circadian rhythm of locomotor activity that entrains strongly to light. Locomotory activity occurs predominantly during the dark phase and can therefore be considered a nocturnal mammal.