September 26, 2022

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Parasites Thrive in Lizard Embryos’ Brain

When Nathalie Feiner noticed a little nematode worm wriggling in an embryonic lizard’s brain from the French Pyrenees, she considered it was a freak incident. She was dissecting hundreds of frequent wall lizard embryos for a analyze and had by no means encountered this invader before—but soon she began finding them in extra of the still unhatched reptiles’ brains.

Intrigued, Feiner, then with the College of Oxford, and a colleague examined the embryos’ parents. They discovered nematodes only in the ovaries of moms that had developed contaminated embryos, suggesting the parasites had been migrating to their offspring in a way scientists had considered extremely hard.

Parasites these types of as nematodes, which do not multiply in their hosts, normally move from mom to kids as a result of mammals’ placentas or milk. But scientists had assumed that in birds and reptiles, the eggshell that types all-around the establishing animal acts as a barrier to these types of invasions. Parasite infection as a result of a reptile egg had by no means been observed in advance of, Feiner says: “It would seem like we have hit on an entirely new life style that these nematodes have developed.”

For a paper approved by the American Naturalist final December, Feiner and her colleagues examined 720 eggs laid by 85 female frequent wall lizards from six locations. The scientists discovered the nematodes in lizards from only that first Pyrenees populace. Contaminated women transmitted the parasite to concerning fifty and 76.nine p.c of their embryos.

DNA investigation confirmed these nematodes are related to, while substantially scaled-down than, a species discovered in the lizards’ gut scientists say they could have developed from that species.

Feiner says scientists could have skipped the chance of egg transmission mainly because they have generally appeared at parasites in birds and turtles, whose eggshells sort soon right after fertilization when the embryo is just a clump of cells—too modest to act as a host. But in lizards and snakes, the shells sort when the embryo is even larger, generating parasite transmission extra plausible. James Harris of the Exploration Middle in Biodiversity and Genetic Means in Portugal, who was not included with the work, says this sort of transmission could be common if the team’s speculation is right.

Feiner suspects the nematode could alter its host’s behavior—a system brain parasites normally use to infect an animal’s predators. For instance, mice contaminated with Toxoplasma fall their tendency to stay away from cat urine. This helps make them extra very easily eaten, transmitting the parasite to the future element of its life cycle. “Identifying the presence of ‘our’ nematode in a predator of the European wall lizard would make [this method] extra likely,” Feiner says.