Imagine discovering that your pearl necklace was actually a string of parasites gorging themselves on your bodily fluids. That’s what happened to a baby spider in Brazil. But instead of helping the unfortunate arachnid, a team of researchers gleefully declared it the country’s second known spider-parasitic mite.
In truth, it would’ve been too late anyway; the researchers spotted the juvenile spider, measuring just a few millimeters long, in a zoological collection.
Ricardo Bassini-Silva, curator of the Acarological Collection at the Zoological Collections Laboratory of the Butantan Institute, recognized what looked like a (chunky) pearl necklace as mite larvae. He and his colleagues’ study, published in October in the International Journal of Acarology, represents Brazil’s second record of spider-parasitic mites and the first of this mite family. They also describe a new species of spider.
Tiny mites on tiny spiders
The team found the mites on three juvenile spider families, and to make matters even nastier, they were all engorged—swollen in size from all that sucking. If you’re completely grossed out by all of this, you’ll be relieved to learn that the entire ordeal transpired on an exceptionally small scale. The mites are a mere millimeter in size, and their spider victims are just a few millimeters long (one millimeter is 0.04 inches). The mites themselves are also babies; for now, researchers know this new species only in its larval form.
“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,” Bassini-Silva explained in a statement by the São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo, or FAPESP).
Young animals are more likely to fall victim to predators and parasites. As such, these mites might have acted opportunistically, given the age of their hosts.
Spider mites suck lymph—a fluid in some arthropods—from between the spider’s abdomen and cephalothorax, an area called the pedicel. “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.
A new spider species
Researchers collected the unfortunate arachnids near grottos and caves in Rio de Janeiro state, a region similar to where Brazil’s first known spider-parasitic mite, Charletonia rocciai, was discovered. At least one of the spiders belongs to a previously unknown species, Araneothrombium brasiliensis.
“This discovery expands the known distribution of the genus Araneothrombium, which was previously only recorded in Costa Rica, to now also include Brazil,” the researchers wrote in the study. “With this new record, the genus is confirmed to occur in at least two countries in the Neotropical region,” they added, indicating that other Neotropical nations might also host its members.
Other members of the arthropod phylum, such as insects, might be plagued by the same mites. As if this wasn’t enough, Bassini-Silva said that Brazil is a great place to find previously undiscovered parasitic mites—the country has over 3,000 spider species.
Yikes.
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