Calling someone a sloth (los peresosos, or “the lazies” in Spanish) is not the way to begin a friendly conversation or a life-long friendship, although these slow-moving animals are a source of constant wonder to biologists, ecologists — and should be to skin researchers. This post aims to elevate the sloth to the same level of respect as the zebrafish, knock-in and knock-out mouse, and the fruit fly.
Twenty percent of the body mass of the sloth is comprised of hair and skin, and sloth nails are several inches long, resembling those of an alien from a faraway planet. The skin of the three-toed sloth (Bradypus spp) is a complex biological community, with about 100 pyralid moths (Cryptoses spp) per animal and a large mass of algae (Trichophilus spp) living on its hair. The current hypothesis is that the moths digest food stuffs for the algae which grow hydroponically in grooves and hair crevices and form a food source for the sloth. When the sloth is lazy (all the time) and bored of eating leaves, there is nothing like a good algal meal from its own hair garden for rounding out the diet. The sloth keeps this biosystem churning, an example of “biological mutualism,” by leaving the trees once a week to defecate and form a rich nest (using its vestigial tail as a spade) for moth larvae. This is a dangerous proposition, because a predator can catch the sloth when it leaves the trees for its toilette. Life is not all rest and munching for the sloth, as it may become the early morning meal for the harpy eagle, whose talons can lift it from the forest canopy.
The sloth certainly deserves respect for its complex and creative evolution — and for stimulating lots of biological research (Pauli et al, 2014)
Pauli JN, Mendoze JE, Steffan SA, et al A syndrome of mutualism reinforces the lifestyle of a sloth (2014) Proceedings of the Royal Society B,281:20133006
This work, accessed on wikipedia, has been released into the public domain by its author, Tauchgurke.