This Newly Discovered Parasite Looks Like a String of Pearls Around a Spider's Neck

Huntsman spiders of the family Sparassidae are found throughout Brazil. While adults can grow to large sizes, with legspans of up to six inches, juvenile spiders are only a few millimeters long. This may explain why a new species, growing from the necks of some young Huntsman spiders in an institute archive in Brazil, went undiscovered for so long.

It was only through careful analysis that researchers at the Butantan Institute in São Paulo, Brazil, noticed that one young Huntsman in their Zoological collection was carrying some unwanted cargo.

They realized the spider was “wearing” a ring of spheres around its neck, like lumpy jewelry. Now, the research team has published a paper revealing that this “necklace” was made from the larvae of an entirely new species.

The paper was published in the International Journal of Acarology.

Parasites Don’t Spare Spiders

Spiders, like many animals, are targeted by parasite predators. These parasites can be scary — some parasitic fungi turn infected spiders into zombies by interfering with their nervous system — but others are just out for a free meal. Spider-parasitic mite larvae, like those from the genus Araneothrombium, grow fat on fluids drained from spider bodies.

This genus was first described in Costa Rica in 2017. Spider-parasite mites are difficult to detect as adults.

“For this group of mites, it isn’t uncommon to know many parasitic species only through their larvae, since in adulthood they become free-living predators, living in the soil and feeding on small insects and even other mites, which makes them very difficult to find,” said Ricardo Bassini-Silva, a researcher and curator of the Acarological Collection at the Butantan Institute, who co-authored the paper, in a press release.

Despite the country’s vast spider ecology, there has only been one previous identification of a spider-parasite mite in Brazil. These earlier mites, Charletonia rocciae, belonged to an entirely different family.

Studying A Spider Parasite Under The Microscope

The researchers named the new species Araneothrombium brasiliensis and used light microscopy and scanning electron microscopy to study the specimens in detail. The mites were around half a millimeter long and were engorged with lymph, a fluid that runs through spiders’ bodies.

They were attached around the spiders’ heads so they could access the pedicel, an area between the spiders’ cephalothorax — where a Huntsman’s two rows of four eyes are found — and their abdomens.

“This is the spider’s most vulnerable region since other parts have a lot of chitin, which forms an exoskeleton difficult for the mites‘ fangs to penetrate,” said Bassini-Silva. The spider mite had rooted themselves onto very young spiders, which may be more vulnerable to parasites.

Bassini-Silva and his team found the parasitized spiders in the state of Rio de Janeiro, in the Pinheiral municipality. The spiders were found near networks of caves and grottoes, a similar location to that where Bassini-Silva and his colleagues previously found Charletonia rocciai specimens.

They published about this earlier discovery in 2022 in the International Journal of Acarology. Charletonia rocciai not only parasitizes spiders, but also targets at least two different orders of insects, suggesting that other animals may also be targets for Araneothrombium brasiliensis.

“With more than 3,000 species of spiders alone, Brazil has immense potential for discovering new parasitic mites,” said Bassini-Silva. The discovery of the mite in Brazil suggests these species might be present, tucked away around spiders’ necks, in many more tropical countries.

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