Neurohumoral basis of circadian rhythmicity inNephrops norvegicus(L)

Sensory biology and behaviour of Nephrops norvegicus

The Norway lobster is one of the most important commercial crustaceans in Europe. A detailed knowledge of the behaviour of this species is crucial in order to optimize fishery yields, improve sustainability of fisheries, and identify man-made environmental threats. Due to the cryptic life-style in burrows, the great depth and low-light condition of their habitat, studies of the behaviour of this species in its natural environment are challenging. Here, we first provide an overview of the sensory modalities (vision, chemoreception, and mechanoreception) of Nephrops norvegicus. We focus particularly on the role of the chemical and mechanical senses in eliciting and steering spatial orientation behaviours. We then concentrate on recent research in social behaviour and biological rhythms of Nephrops. A combination of laboratory approaches and newly developed tracking technologies has led to a better understanding of aggressive interactions, reproductive behaviours, activity cycles, and burrow-related behaviours. Gaps in our knowledge are identified and suggestions for future research are provided.

A new laboratory radio frequency identification (RFID) system for behavioural tracking of marine organisms

Radio frequency identification (RFID) devices are currently used to quantify several traits of animal behaviour with potential applications for the study of marine organisms. To date, behavioural studies with marine organisms are rare because of the technical difficulty of propagating radio waves within the saltwater medium. We present a novel RFID tracking system to study the burrowing behaviour of a valuable fishery resource, the Norway lobster (Nephrops norvegicus L.). The system consists of a network of six controllers, each handling a group of seven antennas. That network was placed below a microcosm tank that recreated important features typical of Nephrops' grounds, such as the presence of multiple burrows. The animals carried a passive transponder attached to their telson, operating at 13.56 MHz. The tracking system was implemented to concurrently report the behaviour of up to three individuals, in terms of their travelled distances in a specified unit of time and their preferential positioning within the antenna network. To do so, the controllers worked in parallel to send the antenna data to a computer via a USB connection. The tracking accuracy of the system was evaluated by concurrently recording the animals' behaviour with automated video imaging. During the two experiments, each lasting approximately one week, two different groups of three animals each showed a variable burrow occupancy and a nocturnal displacement under a standard photoperiod regime (12 h light:12 h dark), measured using the RFID method. Similar results were obtained with the video imaging. Our implemented RFID system was therefore capable of efficiently tracking the tested organisms and has a good potential for use on a wide variety of other marine organisms of commercial, aquaculture, and ecological interest.