The mythological Medusa was feared and reviled for her looks. The snakes that emerged from her head made her more than just odd and ugly. They, along with her visage, turned even the strongest warrior into a rock statue.

This fate will not befall those of us that gaze inquisitively at the medusas of the sea. Medusas are the adult life cycle of many members of the Phylum Cnideria, which include jellyfish as well as other jellyfish-like creatures known as hydroids. These animals are currently out and about in our coastal waters. Their appearance is a little early, likely due to the already warm water temperatures.

Floating provides the best possibility for propulsion for all cniderians. Though these simple marine animals can pulse and contract, true momentum comes from the motion of the ocean and turns of the tide. Both jellyfish and hydroids are considered plankton, since they cannot make their own way; rather, they drift with the tides and currents, at the whim of the water’s ways.

And unlike Medusa’s victims, jellyfish are anything but hard and stony. In fact, these clear, gelatinous blobs are just the opposite, and they are mostly water.

A few types of “true” jellyfish, including moon jellyfish and lion’s mane jellyfish, are the ones that usually cross our paths. Last week, a unique medusa, a hydromedusa, was found in Sengekontacket Pond.  

This was a new species for me, a mystery medusa that had meandered my way. It was about the size of a penny, with a clear and gelatinous body that had a cross of brown visible within its body cavity. With some sleuth work, it was determined to be an angled hydromedusa, also called a clinging jellyfish, orange striped jellyfish, or spider medusa. This cling-on likes to hold onto to eelgrass and other seaweeds. Interestingly enough, it is a Pacific Ocean species that was first found on the East Coast in Woods Hole in 1894 and was subsequently used as an experimental animal at the Woods Hole Institute.

Hydromedusas are in a class by themselves. They are not in the same biological class, Scyphozoa, with those aforementioned familiar “true” jellyfish varieties. Hydromedusas are in the class Hydrozoa, though they lead a similar multifaceted lifecycle.

Life is not boring for the hydromedusa. It has both a mobile and sessile stage, and alternates between a sexual and asexual reproductive cycle. They are most commonly noticed when they are in the medusa or adult form, which can be either male or female. Reproduction is achieved by the release of sperm and eggs into the water. The fertilized eggs grow, and become swimming larvae. A swimming larva will soon attach itself to a substrate, and then proceeds in a manner alien to us mammalian types: the larva starts colonizing itself by asexual budding. Once the colony matures, a bud breaks off and becomes a medusa, starting the cycle all over again. It is this blend of the familiar and the unfamiliar in its reproductive cycle that makes the medusa such a fascinating creature.  

Most hydromedusas are found in saltwater, although there are a few freshwater species. They can live from a few hours to a few months. Typically, they are smaller than a quarter and usually don’t sting, though the largest hydromedusa measures in at about one foot in diameter. Needless to say, the longer their tentacles the more they’ll resemble the snakes growing like hair out of the head of the mythical Medusa. But don’t fear; the only thing that will stop you dead in your tracks when seeing one of these creatures is its unusual appearance, nature and life cycle.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.