Moon Jelly – Monterey Bay Aquarium, Monterey, California

The ghostly moon jelly travels across the open sea. A moon jelly isn’t just a passive drifter – it can swim on its own too. It gently pulses to move within the currents, traveling up and down and back and forth to find food. These alien-looking creatures are named for their translucent, moonlike circular bells. Instead of long, trailing tentacles, moon jellies have a short, fine fringe (cilia) that sweeps food toward the mucous layer on the edges of the bells. Prey is stored in pouches until the oral arms pick it up and begin to digest it.

The coloration of a moon jelly often changes depending on its diet. If the jelly feeds extensively on crustaceans, it turns pink or lavender. An orange tint hints that a jelly’s been feeding on brine shrimp.

Scientists have studied the life cycle of this jelly extensively. They know the adult male moon jelly releases strands of sperm, which are ingested by female moon jellies. After fertilization, larvae settle on or near the seafloor and grow into polyps. Polyps alternate between feeding and reproductive stages for up to 25 years. In the reproductive phase, polyps launch buds of cloned juveniles, known as ephyrae, which grow into adult medusae.