This spider makes its home in the burrows of extinct giant ground sloths

Deep in the unyielding darkness of a Brazilian cave, a pale, blind, spiny beast carefully feels its way across rust-colored rocks. Meet Paleotoca diminas, a spider new to science.

The species, described August 5 in Taxonomy, makes its home in unusual subterranean lairs: the long-abandoned burrows of extinct megafauna, such as giant ground sloths or giant armadillos, researchers say. 

Arachnologist Igor Cizauskas of the Biodiversity Research Support Organization in São Paulo and colleagues found the P. diminas spiders in iron-rich caves in the Brazilian state of Minas Gerais. About two millimeters long, the spiders are a desaturated yellow, lack eyes and have prickly legs. They also sport specialized hairs often used by arachnids for sensing vibrations through the air — an adaptation for life in permanent darkness (SN: 10/15/16).

Careful examinations of the spiders’ physical features suggest the species is a type of long-spinneret ground spider. But certain characteristics of the newfound spiders’ genitalia and legs indicate the arachnids also represent a previously unknown genus, which the researchers have dubbed Paleotoca.

The name means “old house,” a nod to the peculiar variety of cave that the spiders call home — a paleoburrow. Long gouges in the cave walls indicate a giant ground sloth excavated the burrow, the team says.

P. diminas isn’t the only Brazilian arachnid species known to inhabit paleoburrows. Cizauskas and colleagues previously have described two others.

The team’s work has been bolstered by recent legislative changes that prioritize conserving subterranean ecosystems, Cizauskas says. Continued study of the spiders living in these dark and fragile habitats is “a fundamental part of the preservation of these ecosystems in Brazil,” he says.