In the depths of the tropical jungle of Papua New Guineaa fortuitous finding that occurred more than three decades ago opened one of the lines of more intriguing research in bird biology.
Is that what began as a scratch on the lips of a young ornithologist resulted in the discovery of unsuspected capacity in some birds: being toxic.
During the summer of 1989, Jack Dumbacherthen postgraduate student in the University of Chicagohe was in his first field expedition. While checking the fog nets installed to capture birds for study purposes, a specimen of black and orange plumage scratched him. When he took the cut to the mouth, he felt a persistent burning followed by numbness.
When the episode to the locals, they identified him as a hooded pitohuia species that avoided consuming, unless it was carefully prepared, for their well -known toxicity.
The incident motivated Dumbacher To investigate the origin of unusual sensations. In 1992, together with a team of collaborators, he confirmed that the Pitohui Dichrou It contained batracotoxin, one of the most powerful alkaloids of the animal kingdom, and the same one that is in certain venomous dart frogs of South America. This was the first documented case of a poisonous bird.
Since then, the scientific community has identified at least a dozen species of toxic birds, among the more than 10,500 known. Most are in New Guineaincluding at least five additional species of Pitohui and the blue -head. Poisonous birds have also been reported outside the island, such as European quail, Canadian urogal and abubillas, although these have different toxins. The concentration of species with batracotoxin in the same geographical region raises still open questions about its ecology and evolution.
A persistent hypothesis suggests that birds do not synthesize batracotoxin by themselves, but incorporate it through their diet. The beetle of the genre Choresine It has been indicated as the possible source. However, Dumbacher, who in 2004 was the first to describe the presence of Batracotoxin both in birds and insects, doubts that beetles are the original producers. “Most of the information suggests that beetles cannot produce these steroid alkaloids”, He said, and proposed as an alternative other organisms of the environment, such as soil mites or plants not yet identified.
To track the origin of toxin, researchers led by the ecologist Knud Jøsson and the biologist Kasun Wedowatta They seek to compare the stomach content of toxic birds with that of insects trapped in nearby areas. “It’s like looking for a needle in a haystack, but that is the first step we can take”, Jøsson told National Geographic. Likewise, in collaboration with Chemistry Christine Beemelmannssix derivatives of batracotoxin have been identified so far in collected samples.
Batracotoxin affects sodium channels in muscle, nervous and cardiac cells, causing a continuous opening of these channels, which can lead to paralysis and even death. Some South American poisonous frogs have mutations in genes that encode those channels, preventing toxin from adhering. A similar hypothesis was applied to toxic birds.
Jøsson and his team compared the genomes of six poisonous species with related non -toxic birds and found mutations in genes that encode a specific sodium channel.
However, when the biophysicist Daniel Minor He replied these channels in laboratory experiments, discovered that they were still vulnerable to batracotoxin, which contradicted the hypothesis. Minor then proposed an alternative: birds could produce a “sponge” protein, not yet identified, capable of joining toxin and neutralizing it before it causes harm.
This mechanism would remember saxifilin, a protein that kidnaps saxitoxin in poisonous frogs. “Our laboratory showed that saxifilin can absorb and join saxitoxin with great affinity,” said Minor, which led to think that there could be a similar mechanism in birds.
After more than a decade without discoveries, the team of Jøsson and Bodawatta He identified in 2023 two new species of poisonous birds. They plan to continue their field work in New Guinea Until 2028, with annual visits and an intensive sampling collection campaign. Its objective is to expand the genetic map of venomous birds, focusing on the species of the crowd superfamily, which includes about 700 species worldwide, 140 of which are found in New Guinea. Until now, only one fifth of them has been studied.
In addition to identifying new species, the equipment will sequence the genomes of multiple individuals by species to detect mutations in sodium channels and look for proteins with functions similar to those of saxifilin.
Beyond the specific case of New Guinearesearchers are interested in the “convergent evolution” that would have allowed unrelated animals – ranges, birds, fish and octopuses – to develop similar mechanisms to resist mortal toxins. “Understanding converging adaptations by natural selection is a central objective in evolutionary biology”Jønson said.
The implications are wide: it is not just identifying new poisonous organisms, but about understanding how independent evolutionary processes can reach similar biological solutions against common toxic challenges. As wedowatta stressed: “Perhaps in two or three years we have new knowledge to share. This is just the beginning”
