Scientia Marina, Vol 69, No 3 (2005)

Temporal modification in cardiac rhythmicity of Nephrops norvegicus (Crustacea: Decapoda) in relation to trawl capture stress


https://doi.org/10.3989/scimar.2005.69n3369

Jacopo Aguzzi
Institut de Ciències del Mar (CSIC), Spain

Juan Chiesa
Chronobiology Unit, Faculty of Pharmacology, University of Barcelona, Spain

Pere Abelló
Institut de Ciències del Mar (CSIC), Spain

Antoni Diez-Noguera
Chronobiology Unit, Faculty of Pharmacology, University of Barcelona, Spain

Abstract


The effects of trawling on cardiac rhythmicity of Nephrops norvegicus (L.) are still mostly unknown. Ultradian rhythms reported in previous studies may result from trawling capture stress, thus disappearing following acclimatisation to laboratory conditions. To test this hypothesis, 34 time series of cardiac activity data recorded in constant darkness were studied by Fourier analysis. Spectral decomposition of time series was obtained by defining the fundamental or circadian harmonic (CH) in 24-h together with 9 submultiples of this period. The power content (PC) of each harmonic was estimated in data segments of 24-h duration (days), giving graphic matrices of PC values over consecutive days. Values of PC for 9 submultiples were summed and studied in a block named ultradian band (UB). The modification in the PC of the CH and of the UB was evaluated during laboratory acclimatisation. A significant increase in the PC of the circadian harmonic component (CH) over consecutive days of testing was observed. These findings suggest that, rather than being a product of dim light environmental fluctuations experienced by the animals from the deep waters of the continental slope, ultradian periodicity could well be caused by the stress of capture.

Keywords


Nephrops norvegicus; stress; cardiac rhythms; constant darkness; Fourier analysis; circadian and ultradian rhythms

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