“The common frog in the Donana National Park has not yet adapted to the American crayfish,” said Iván Gómez Mestre. To verify this, researchers have confronted two groups of tadpoles with the American red crayfish (Procambarus clarkii), and compared the degree of activation of their defenses. Both the common frog tadpoles in the wetlands of Donana, a town three decades has been in contact with this predator (between 10 and 15 generations), and tadpoles from populations that are faced by first time crab responded the same way: “The degree of activation of defenses is the same in both cases: null,” says the biologist.

Tadpoles, explains, they have many defenses available to it, but when they detect the chemical signals (the smell dissolved in water) of a predator such as dragonfly larvae can morphological and behavioral changes. “The changes in shape result in a wider tail and more pigmented, which attracts the predator to her leaving intact the vital organs and no tears or loss of tail have such serious consequences, since they can regenerate. And changes in behavior resulting in a reduction of activity that passed over unnoticed, “said Ivan Gomez Mestre.

But these changes, despite improved survival in case of predators, have a price: “By reducing its activity, the tadpoles were fed less, grew more slowly and faced with the progress of your pond dry season, addition to give advantage to competitors for food, “says the researcher. Hence, the activation of defenses is not permanent and depend on the detection of the predator species by the tadpoles.

An evolutionary race
The results published today contribute to better understand the series of changes that occur in the Iberian ecosystems that invasive crab, native to the Southeastern U.S. and present from Donana to Asturias. As indicated by Ivan Gomez Mestre, among other effects “are known to be in areas that present the American crayfish is a proliferation of predatory birds, so that the pressure on amphibians increases even more.”

“The question is whether common frog populations exposed to American crayfish have enough time before dying to adapt to the presence of an introduced predator so voracious. Can not venture a period in evolutionary terms, because each species responds differently, but a reference can be detected cases in the U.S. adaptation of bullfrog tadpoles by introduced fish against the man after 110 years of contact, “says researcher.

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Boston University CSIC
Ivan Gomez Mestre he worked at Boston University for five years, the first two thanks to a postdoctoral fellowship from the Ministry of Education and Science, and the next three hired by Boston University. They focused on the evolution of antipredator behavior of tropical tree frogs, especially in Costa Rica. Now, having returned to Spain in the framework of the I3 of the Ministry of Science and Innovation, is Ramón y Cajal investigator assigned to the Joint Research Unit for Biodiversity Asturias CSIC-Universidad de Oviedo.

The American crayfish in Asturias:
The species was detected 15 years ago in Asturian rivers. The American crayfish damage native ecosystems and particularly harmful to salmonids, small fish, amphibians, and vegetation waters. It has also displaced the native crayfish ( Austropotamobius pallipes lusitanicus ) in almost all waterways. This situation has led to initiatives such as the Crab Project: http://elbanzao-proyectocangrejo.blogspot.com/

Source: FICYT