Hydrodinamic entrainment of behavioural rhythms in the deep-sea benthic organisms: Nephrops norvegicus (Crustacea: Decapoda) as a model

Abstract

Light and tidal cycles are the most important entraining agents for biological rhythms in shallow water marine ecosystems while little is known for the deep-sea. As light decreases with an increasing depth, internal tides and inertial currents seem to act as synchronizers for behavioral rhythms in the deep-sea. Unfortunately, an endogenous basis for these rhythms has still not been demonstrated in the laboratory. Decapods are frequently used as models for chronobiological investigation. In laboratory experiments the Norway lobster, Nephrops norvegicus, has been shown to exhibit marked diel (i.e. 24h) patterns in its burrow emergence, even if ultradian fluctuations (i.e. < 24h) often occur. Because of the low light conditions, animals of deeper habitats (i.e. upper slope) may respond to hydrodynamic stimulation in geographical contexts were internal tides are strong (e.g. Atlantic Ocean). Here, we describe a new deep-sea research scenario and the consequential technological implementation that includes the functioning of a newly created and fully automated actograph based on mini-flume aquaria. We will also describe the preliminary results obtained in relation to the potential internal-tidal synchronization of the emergence rhythms of the Norway lobster