The study consisted of an experiment developed in the Centre for Environmental Biology in Grndola (Portugal), where the larvae of the five populations were raised from tadpoles to metamorphosis in the presence or absence of the red swamp crayfish.
"We held them in aquariums with a compartment into which a red swamp crayfish was introduced, or it was left predator-less. We also fed the predators in these compartments with larvae so that they produced chemical signals indicative of predation which could be detected by the larvae in the experiment," Orizaola explains.
Using this design of experiment, they analysed the response, both of the behaviour and the morphology of the P. perezi frogspawn in the presence and absence of the predator.
According to the scientist, the results reveal that the populations of these amphibians with a tradition of coexisting with the predator for 30 years (between 10 and 15 generations of frogs) present a pattern of activity that is totally different from the populations with less coexistence or no coexistence with the red swamp crayfish.
"A long coexistence with the predator generated extraordinarily reduced patterns of activity, even in the absence of the predator. This would help the larvae to go unnoticed, which would help to increase its chances of survival," Orizaola points out. On the other hand, the other populations were five times more active.
Bigger tails and bodies
In terms of their morphology, the larvae of populations which have coexisted with the red swamp cray
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