Hydrodynamic, non-photic modulation of biorhythms in the Norway lobster, Nephrops norvegicus (L.)

Data on biological rhythms of the Norway lobster Nephrops norvegicus (L) are compared with new findings on inertial currents. a non-photic geophysical hydrodynamic fluctuation. Laboratory experiments on animal endogenous cardiac activity and locomotor rhythms using individuals from the middle slope (400-600m depth) of the Mediterranean Sea revealed a consistent proportion of ultradian 18-h animals (20.6% and 12.0% of the studied cases for cardiac and locomotor tests, respectively). This characteristic, not reported in similar experiments with individuals from shallower depths (20-200 m) in the Atlantic Ocean, was initially considered meaningless from an ecological point of view. However, a close comparison with in situ oceanographic measurements over 1 year revealed a clear relationship between inertial current fluctuations and the observed 18-h behavioural and physiological rhythms. We propose a novel scenario involving potential non-photic (i.e. hydrodynamic) modulation of Nephrops biorhythms, and suggest that this may provide a paradigm for other benthic species in deep-water areas. (c) 2008 Elsevier Ltd. All rights reserved.