Behavioural ecotoxicology of the brown shrimp, Crangon crangon : changing colour in polluted environments

The brown shrimp, Crangon crangon has a great ecological value in UK estuaries and coastal areas and it is also a commercially important species. It utilizes chromatophores (specialized cells containing pigments) to match its background, changing its colour either from pale (pigments contracted) to dark (pigments expanded) or vice versa, thus becoming almost invisible in its environment. Chromatophores also protect the shrimp (at least in the larval stages) from UV light. The control of pigments depends on hormones, secreted by the shrimp as a response to different stimuli (e.g., light, temperature and colour of substrate). Contaminants are found often and consistently in estuaries, due to human activities along the coasts and can potentially affect behavioural responses, acting as anthropogenic stressors. The use of colour change as a behavioural marker of pollution is considered here, as a potential effective tool to assess the initial stages of biological alteration in aquatic organisms. To test the efficiency of this novel technique, brown shrimp have been treated with non-lethal concentrations of cadmium (Cd) plus two different antibiotics [Gentamicin (Gt) and Furazolidone (FZN)] and arsenic (As). A great interindividual and interpopulation variability in response to the use of heavy metals and antibiotics was found. Therefore, colour change ability in the brown shrimp is not a sensitive behavioural ecotoxicological marker to detect early stages of contaminations in the environment, at least for Cd, As, Gt and FZD. Finally, given the high level of total As often detected in seafood, a speciation analysis was performed in the dosed specimens. The quantification of the various As species through time suggest the possibility of the brown shrimp to bio-transform inorganic arsenic (iAs) into the less toxic organic form [arsenobetaine (AsB)]. This has relevant implications for aquaculture and fisheries of crustaceans in areas contaminated by inorganic As: shrimp can be consumed by humans even if grown in contaminated areas, and potentially could detoxify water from iAs. However, more investigations are needed, leaving this field open to applied studies in the field