Jelly Fish!

Today we we were treated with a "smack" of Moon Jellies at the Rosario Resort Marina in Cascade Bay, some of the most simple and incredible creatures in Puget Sound. Moon Jellies are probably the most common jellyfish in the Northwest, and they have transparent, milky white bells rimmed with hundreds of short, hair-like tentacles.

Though they are called "jellyfish," Moon Jellies aren't really fish at all. Instead, they are considered Hydrozoa, and they have no heads, no skeletons, and no special organs for respiration or excretion. Their scientific name is Aurelia aurita, which comes from the Latin word for "light." Some scientists think Moon Jellies got this name because, instead of eyes, they have special cells called rhopalia that detect light.

Moon Jellies are found in the Atlantic Ocean from the Arctic to Florida and Mexico, and in the Pacific Ocean from Alaska to southern California. They're also found right here in Puget Sound! Huge masses of them are called smacks, which drift with the current near the beach.

The Jellies swim by expanding and contracting their bell, an action that forces water away and pushes the critter in the opposite direction. Every Moon Jelly also has four oral arms, frilled along one edge, hanging from the center of this bell. The four horseshoe shapes you spot in the center of the bell are the gonads, or sex organs. In young Moon Jellies, called polyps, these gonads are white. In mature animals, dubbed medusas, the gonads are tinged with color. 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. (Moon Jelly information courtesy of the Seattle Aquarium).

It was an incredible sight!

Go to Rosario Resort Web Site