Spiders freak people out just by existing, but they also have a quality some might consider creepy: They shed their skins.
Regular skin peels are routine for other creatures, too, which inspired Weird Animal Question of the Week to look into this intriguing process of renewal. (See 10 beautiful pictures that will make you love spiders.)
Growing larger causes spiders to molt, a process called ecdysis, Jo-Anne Sewlal, an arachnologist at the University of the West Indies, says via email.
Tarantulas, as the above video shows, “secrete a new exoskeleton around itself while it is still encased in the old exoskeleton,” Sewlal says. (See "Bondage, Cannibalism, and Castration—Spiders' Wild Sex Lives.")
The living tissue between old and new will dissolve, except for nerve connections to sensory organs like eyes and touch-sensitive hairs.
To get things going, the tarantula contracts its abdomen to push fluids into the cephalothorax, its fused head and upper body. This pressures weak spots in that segment so the old exoskeleton “lifts off like a helmet,” Sewlal says.
Finally the spider flips over and slides out of its old legs like a pair of jeans—et voilà, the tarantula’s new clothes. (Also read "50 New Spiders Discovered In Australia.")
“The spider’s new exoskeleton looks wrinkled and quite pale, not at all like its old one,” she adds. The new skin is also softer at first, making the arachnid more vulnerable to predation.
Crabs generally take about 15 minutes to exit their old shells, under which a thin new shell has grown. The animals' bodies release enzymes that cause their old shells to begin separating, as well as take on seawater to help pry it open. (Watch a video of a giant spider crab shedding.)
Snakes are famous for slinking out of their skins, says Laurie J. Vitt, curator emeritus of reptiles at the Sam Noble Museum in Oklahoma.
Injuries can also cause reptiles and amphibians to molt, he says. (Related: "New Gecko Sheds Skin on Demand, Looks Like Raw Chicken.")
For instance, someone once brought Vitt a snake that had been hit in the head, triggering a "continuous shedding cycle ... about once a month until it died."
The deepest layer of skin in reptiles and amphibians produces new cells, which move upward to the top layer and mature, according to Vitt.
The first outward sign that a snake is ready to shed is that its eyes turn a milky color.
Patches of mucus between the lower and upper layers of skin begin to appear. As the mucus increases, the layers disconnect and eventually the old layer splits, usually at the top of the head, then down the back.
Shedding skin not only frees up room, for some geckos and anoles, it's also a snack, Vitt says. Notably, snakes will not eat their old skin.
Haven’t they heard of recycling?