Field observations in Doñana showed that these ants caused death by contact with their venom to juvenile amphibians.

The Argentine ant, the new threat to amphibians.

An international team led by the Doñana Biological Station (EBD), center of the Higher Council for Scientific Research (CSIC) in Seville, has shown that the venom of the Argentine ant has negative effects very powerful on some amphibians of Doñana, even being lethal for them. The investigation has appeared published this past dawn in the magazine Conservation Biology.

This kind of ant, whose native range is the Paraná basin (Argentina, Brazil, Uruguay), has invaded the whole world, mainly the regions with a Mediterranean climate. Unlike other large invasive ants, does not have a functional stinger, so its use of the poison is by contact. Field observations in Doñana have shown that these ants caused the death of juvenile amphibians that they encountered.

The study, in which scientific teams from France, Israel, Belgium and the United States also participated, is part of the doctoral thesis of Paloma Álvarez-Blanco, directed by Elena Angulo, researcher specialized in invasive ants, previously linked to EBD and currently working at the Paris-Saclay University.

The subsequent laboratory study revealed that the toxin contained in the venom of this invasive ant species, called iridomirmecin and produced in the pigidial glands, was used to attack amphibians by spraying it on the permeable skin of juveniles and causing paralysis. After absorption through the skin, iridomirmecin accumulated in the brain, kidneys, and liver tissue, and could be fatal depending on the dose received and the size of the amphibian.

The most vulnerable

The amphibians most vulnerable to the poison of the Argentine ant are the spur toads and the runner toad. Although Argentine ant workers are small, weighing less than half a milligram, it would take between 2 and 20 of them to kill the juveniles of these toads.

On the other hand, the native ant of the region, Tapinoma nigerrimum, does not have no negative effect on amphibians, since, although it also has iridomirmecin in its body, it is found in an amount five times less than in the Argentine ant.

For determine the potential global reach of this new threat with which amphibians face, the researchers estimated the number of terrestrial amphibian species whose distribution overlaps with that of the Argentine ant: there are more than 800 species of terrestrial amphibians (and of these 6% are classified as threatened by the IUCN) that live with the Argentine ant throughout the world.