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Circadian Rhythms of Locomotor Activity in the Nile Tilapia Oreochromis niloticus

Citation
Vera L, Cairns L, Sanchez-Vazquez FJ & Migaud H (2009) Circadian Rhythms of Locomotor Activity in the Nile Tilapia Oreochromis niloticus, Chronobiology International, 26 (4), pp. 666-681.

Abstract
Behavioral rhythms of the Nile tilapia were investigated to better characterize its circadian system. To do so, the locomotor activity patterns of both male and female tilapia reared under a 12:12 h light-dark (LD) cycle were studied, as well as in males the existence of endogenous rhythmicity under free-running conditions (DD and 45 min LD pulses). When exposed to an LD cycle, the daily pattern of activity differed between individuals: some fish were diurnal, some nocturnal, and a few displayed an arrhythmic pattern. This variability would be typical of the plastic circadian system of fish. Moreover, reproductive events clearly affected the behavioral rhythms of female tilapia, a mouth-brooder teleost species. Under DD, 50% (6 of 12) of male fish showed circadian rhythms with an average period (t) of 24.1+0.2 h, whereas under the 45 min LD pulses, 58% (7 of 12) of the fish exhibited free-running activity rhythms with an average t of 23.9+0.5 h. However, interestingly in this case, activity was always confined to the dark phase. Furthermore, when the LD cycle was reversed, a third of the fish showed gradual desynchronization to the new phase, taking 7–10 days to be completely re-entrained. Taken together, these results suggest the existence of an endogenous circadian oscillator that controls the expression of locomotor activity rhythms in the Nile tilapia, although its anatomical localization remains unknown.

Keywords
Circadian rhythms; Locomotor activity; Nile tilapia; Photoperiod

Subject headings
Nile tilapia; Circadian rhythms; Photoperiodism; Catfishes

StatusPublished
AuthorsVera LM, Cairns Louise, Sanchez-Vazquez F Javier, Migaud Herve
Publication date05/2009
PublisherTaylor & Francis (Informa Healthcare)
ISSN 0742-0528
LanguageEnglish

Journal
Chronobiology International: Volume 26, Issue 4 (2009-05)

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