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The adaptation of bimodal breathing species to the warming of marine waters

In Nature Scientific Reports a research by UNIFI on crabs' strategy
 If the water is too warm the best thing is to catch some fresh air. This strategy adopted by the crabs living in the rocky coastal areas of Tuscany casts some light on a key evolutionary step, the one that permitted the shift from the aquatic ancestors to the terrestrial species, as illustrated in the study published on Nature Scientific Reports. (“The trade-off between heat tolerance and metabolic cost drives the bimodal life strategy at the air-water interface”, doi: 10.1038/srep19158). The project was coordinated by Stefano Cannicci together with colleagues from the Alfred-Weneger-Istitute for Polar and Marine Research, the most authoritative centre in Europe studying climate changes.

The team of researchers has chosen as its study model the most common crabs of the Tuscan coast, the species Pachygrapsus marmoratus, collected in the area of Calafuria. Thanks to physiological tests carried out at the laboratories of the Department of Biology, scientists have proved what are the evolutionary mechanisms used by dual-breathing species to cope with the climatic change causing the warming of sea temperature.

The crustaceans switch from a mainly water-breathing mode to an air-breathing as a way to avoid the fall of oxygen in their tissues due to warmer waters. "We have proved for the first time, explains Stefano Cannicci, associate professor of Zoology, that the warming of ocean waters triggers such an important evolutionary process as the colonisation of land.
"In an age like the present one, characterised by a constant and rapid rise of ocean and atmosphere temperature, continues the scientist, an evolutionary strategy that can be used by species that live between sea and land is, in fact, that of becoming more terrestrial and less marine."

The study - carried out in Florence also by Marco Fusi - proves that above a certain water temperature, ectothermic animals that can breathe - albeit not equally well - both in and out-of-water, choose to come out of the water altogether and take a chance at settling on dry land.

"Crabs, comments Cannicci, allow us to understand how one of the most important evolutionary passages in history that lead to terrestrial species, could have happened.

28 January 2016