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Parasites Thrive in Lizard Embryos’ Brain

When Nathalie Feiner noticed a tiny nematode worm wriggling in an embryonic lizard’s mind from the French Pyrenees, she thought it was a freak accident. She was dissecting lots of of frequent wall lizard embryos for a research and had by no means encountered this invader earlier than—however quickly she began discovering them in additional of the nonetheless unhatched reptiles’ brains.

Intrigued, Feiner, then with the University of Oxford, and a colleague examined the embryos’ dad and mom. They discovered nematodes solely within the ovaries of moms that had produced contaminated embryos, suggesting the parasites have been migrating to their offspring in a means researchers had thought inconceivable.

Parasites resembling nematodes, which don’t multiply of their hosts, usually go from mom to kids by mammals’ placentas or milk. But scientists had assumed that in birds and reptiles, the eggshell that kinds across the creating animal acts as a barrier to such invasions. Parasite an infection by a reptile egg had by no means been noticed earlier than, Feiner says: “It seems like we have hit on an entirely new lifestyle that these nematodes have evolved.”

For a paper accepted by the American Naturalist final December, Feiner and her colleagues examined 720 eggs laid by 85 feminine frequent wall lizards from six areas. The researchers discovered the nematodes in lizards from solely that first Pyrenees inhabitants. Infected females transmitted the parasite to between 50 and 76.9 p.c of their embryos.

DNA evaluation confirmed these nematodes are just like, although a lot smaller than, a species discovered within the lizards’ intestine; researchers say they might have advanced from that species.

Feiner says scientists may have missed the opportunity of egg transmission as a result of they’ve primarily checked out parasites in birds and turtles, whose eggshells type shortly after fertilization when the embryo is only a clump of cells—too small to behave as a number. But in lizards and snakes, the shells type when the embryo is larger, making parasite transmission extra believable. James Harris of the Research Center in Biodiversity and Genetic Resources in Portugal, who was not concerned with the work, says this type of transmission could possibly be widespread if the workforce’s speculation is right.

Feiner suspects the nematode may change its host’s conduct—a way mind parasites usually use to contaminate an animal’s predators. For occasion, mice contaminated with Toxoplasma drop their tendency to keep away from cat urine. This makes them extra simply eaten, transmitting the parasite to the following a part of its life cycle. “Identifying the presence of ‘our’ nematode in a predator of the European wall lizard would make [this strategy] more likely,” Feiner says.

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