17 gennaio 2012

Organismi marini a rischio a causa dell'aumento di anidride carbonica (Carbon dioxide levels alter fish behaviour)

Donzella. Foto: Paolo Domenici Due ricerche coordinate da Paolo Domenici (IAMC-CNR: Istituto per l'Ambiente Marino Costiero, Torregrande, Oristano) analizzano gli effetti negativi sugli organismi marini causati dagli elevati livelli di anidride carbonica negli oceani, come la perdita della naturale tendenza a schivare ostacoli e predatori.
I risultati delle ricerche sono stati pubblicati su Biology Letters il 26 luglio 2011 e su Nature Climate Change il 15 gennaio 2012. Sotto riporto gli abstract e i link al sito delle due riviste.
Nella foto in alto: la Donzella, il pesce usato per gli esperimenti sulla lateralizzazione. Autore: Paolo Domenici

Elevated carbon dioxide affects behavioural lateralization in a coral reef fish Paolo Domenici (IAMC-CNR (Istituto per l'Ambiente Marino Costiero, Torregrande, Oristano), Bridie Allan, Mark I. McCormick e Philip L. Munday (RC Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, Townsville, Australia). Biology Letters, July 26, 2011.
Abstract
Elevated carbon dioxide (CO2) has recently been shown to affect chemosensory and auditory behaviour, and activity levels of larval reef fishes, increasing their risk of predation. However, the mechanisms underlying these changes are unknown. Behavioural lateralization is an expression of brain functional asymmetries, and thus provides a unique test of the hypothesis that elevated CO2 affects brain function in larval fishes. We tested the effect of near-future CO2 concentrations (880 µatm) on behavioural lateralization in the reef fish, Neopomacentrus azysron. Individuals exposed to current-day or elevated CO2 were observed in a detour test where they made repeated decisions about turning left or right. No preference for right or left turns was observed at the population level. However, individual control fish turned either left or right with greater frequency than expected by chance. Exposure to elevated-CO2 disrupted individual lateralization, with values that were not different from a random expectation. These results provide compelling evidence that elevated CO2 directly affects brain function in larval fishes. Given that lateralization enhances performance in a number of cognitive tasks and anti-predator behaviours, it is possible that a loss of lateralization could increase the vulnerability of larval fishes to predation in a future high-CO2 ocean.

Near-future carbon dioxide levels alter fish behaviour by interfering with neurotransmitter function Göran Nilsson (Physiology Programme, Department of Molecular Biosciences, University of Oslo, Norway), Danielle L. Dixson ARC Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, Townsville, Australia), Paolo Domenici (IAMC-CNR Istituto per l’Ambiente Marino Costiero, Torregrande, Oristano), Mark I. McCormick (ARC Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, Townsville, Australia), Christina Sørensen (Physiology Programme, Department of Molecular Biosciences, University of Oslo, Norway), Sue-Ann Watson (ARC Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, Townsville, Australia), Philip L. Munday (ARC Centre of Excellence for Coral Reef Studies, and School of Marine and Tropical Biology, James Cook University, Townsville, Australia).
Nature Climate Change, Published online: 15 January 2012
Abstract
Predicted future CO2 levels have been found to alter sensory responses and behaviour of marine fishes. Changes include increased boldness and activity, loss of behavioural lateralization, altered auditory preferences and impaired olfactory function. Impaired olfactory function makes larval fish attracted to odours they normally avoid, including ones from predators and unfavourable habitats. These behavioural alterations have significant effects on mortality that may have far-reaching implications for population replenishment, community structure and ecosystem function. However, the underlying mechanism linking high CO2 to these diverse responses has been unknown. Here we show that abnormal olfactory preferences and loss of behavioural lateralization exhibited by two species of larval coral reef fish exposed to high CO2 can be rapidly and effectively reversed by treatment with an antagonist of the GABA-A receptor. GABA-A is a major neurotransmitter receptor in the vertebrate brain. Thus, our results indicate that high CO2 interferes with neurotransmitter function, a hitherto unrecognized threat to marine populations and ecosystems. Given the ubiquity and conserved function of GABA-A receptors, we predict that rising CO2 levels could cause sensory and behavioural impairment in a wide range of marine species, especially those that tightly control their acid–base balance through regulatory changes in HCO3− and Cl− levels.

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