Earthworm Love Is Cuddly ... and Complicated | Deep Look

Earthworms know a thing or two about romance. They cozy up with a mate inside tubes of slime, then follow a series of intricate steps to make cocoons full of baby worms. ** TAKE OUR NEWSLETTER SURVEY: DEEP LOOK is an ultra-HD (4K) short video series created by KQED in San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small. --- You can tell an earthworm is ready to mate once it has grown a fleshy patch called a clitellum. When it sidles up to another earthworm, their bodies point in opposite directions, and the worms surround each other with tubes of slime exuded from their skin. The earthworms embrace by using flaps on their clitella, and exchange sperm that travels outside their bodies. As they snuggle, the sperm flows into internal storage sacs. After mating, an earthworm produces a sheath with