A history of recent advancements on Nephrops norvegicus behavioral and physiological rhythms

Abstract

Biological rhythms are a widespread feature of living organisms, being expressed at any level of their organization. Behavioral and physiological rhythms can affect the results on species stock assessment when the timing of sampling is not taken into account. That timing is of importance since animals may be present or not in a certain area of sampling depending on their activity cycle. As an example of this, the rhythmic behavior and physiology of one of the most commercially important European decapods, the Norway lobster (Nephrops norvegicus) was studied. These rhythms affect its commercial catchability at a diel and at a seasonal scale. Nephrops inhabits muddy bottoms where animals dig burrows that save them from the trawl tow capture when occupied. Catch patterns have been widely used as proxy of activity rhythms of populations of different depths. Catches show a modulation upon the day-night cycle since animals emerge under optimum environmental illumination in order to feed. Emergence is also affected in a not fully clarified manner by other variables of environmental and demographic nature (e.g. food presence, hunger state, sex, size, reproductive stage, territorialism and mating). All these features make Nephrops a good model of reference for studies on biological rhythms of other commercially important deep water decapods in relation to their ecological context. In this review, we summarize the actual knowledge on Nephrops behavioral and physiological rhythms. We will compare data obtained from laboratory tests on single individuals with data obtained from trawling of populations of different depths. We will also describe some new hypotheses on the rhythmic regulation of the species behaviour, as well as potential scenarios for future research.

Circadian clocks in crustaceans: identified neuronal and cellular systems

“…However, chronobiological studies have involved multiple crustacean species and are preferably comparative. Most common are studies on locomotory patterns, which are perhaps best documented for the shore crab Carcinus maenas (7,24,25), crayfish (26), and lobsters (27)(28)(29)(30). For C. maenas and species of commercial value such as Homarus americanus, rhythms related to moulting and reproduction have been well documented (31)(32)(33)(34)(35).…”

“…We will not address the overt phenomena accessible to behavioural observation. Many of these were covered previously by excellent reviews concerning aspects of circatidal, circalunar or circadian rhythms of locomotion (3,4,6,7,15), reproduction (30,50), moulting (9,50), and hatching or larval release (6,51). In certain cases, reference will be given only to landmark papers or reviews to provide further detail.…”

A new tracking system for the measurement of diel locomotor rhythms in the Norway lobster, Nephrops norvegicus (L.)

“…Species may be present or absent in a sampling area depending on an activity rhythm, which is controlled by the entrainment of the biological clock by light intensity cycles (Aguzzi and Sardà, 2008). Field sampling to assess activity rhythms of populations and retrieve animals for laboratory tests becomes increasingly difficult at greater depths (Raffaelli et al, 2003).…”

Modeled day–night biases in decapod assessment by bottom trawling survey

“…Animals are collectable only when moving within the benthic boundary layer during phases of active substrate emergence (reviewed by Aguzzi et al, 2009a). Species shift the timing of emergence from night to day as depth increases (Aguzzi et al, 2009a), according to the known "Nephrops model" (reviewed by Bell et al, 2006;Aguzzi and Sardà, 2008). Therefore, these species present maxima in captures with timing dependent upon depth.…”

“…The activity rhythm of commercially exploited resources may consistently bias demographic assessments of their populations (reviewed by Aguzzi and Sardà, 2008). Within a certain sampling area, the assumption of a behaviourally based bias for one population of a species should be assumed also for all populations of different species within the local community.…”