Transcript:

Today on Animal Fact Files we’re discussing symmetrical hermit crabs. Most hermit crabs have a twisted, squishy tail. They crawl around in the shells made by other animals to keep that squishy, twisted tail protected. The twist helps facilitate squishing themselves into the spiraling shells they call home; there are, however, some hermit crab species that don't have that tail twist. These are commonly known as the symmetrical hermit crabs.

There are currently over 40 described symmetrical hermit crab species, but new information will likely lead to changes in this number. They're relatively understudied, especially compared to their asymmetrical relatives, and this is likely partially due to where they live. Symmetrical hermit crabs are benthic creatures, living along the bottom of most temperate and tropical oceans. They're typically found between 650 and 1,600 feet (200-500m) below the waves, though rarely they can be seen about 100 feet (30m) deep and down to nearly a mile (1,600m) under the surface.

Symmetrical hermit crabs don't have that twisty tail, instead they look like small crayfish. In size, they average about a centimeter long, which means an individual could probably fit comfortably on your fingernail. Because they don't have that asymmetrical twist to help them slide into snail shells, symmetrical hermit crabs use other means of keeping themselves protected. Some burrow into wood or other plants, such as bamboo. A mangrove root can make an excellent symmetrical hermit crab home. Others utilize rocks, such as pumice stone. Some use other animals such as sponges or even dead coral fragments. And others use tusk shells which are conveniently not twisty - we have a video for them, too!

Of course, not all of these homes are exactly moveable, so it's believed that symmetrical hermit crabs actually leave their home from time to time in order to forage and find mates. These crustaceans likely eat whatever they can find from small animals floating in the water column or settled on the sand, to organic particles and decomposing material. In turn, they're likely taken by larger predators such as fish, though very little is known about the symmetrical hermit crab's place in the food web! When they are at home in their burrow, however, symmetrical hermit crabs use their claws like a lid to seal them inside.

Even more poorly understood is the lifecycle of these creatures. In rare cases where pregnant symmetrical hermit crabs were observed, the eggs and babies were brooded with the mother and showed advanced development. Basically, they seem to stick with their mom in the safety of a brood-pouch like structure eating only nutrition provided to them by the mother. They remain here as they molt through their larval stages. It's likely they then leave when they look like smaller versions of the adults. This information comes from only a few examples, so there could be vastly different rearing strategies in other species. Plus, it's still unknown how long they live!

For more facts on symmetrical hermit crabs, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! And thank you for watching Animal Fact Files!