Medusa

Medusa
By Barbara Ducote
Fall 97

What is a medusa? When this term is read, one thinks of strange creatures from Greek and Roman mythology. Yet medusas offer a unique addition to the estuary systems. Medusa or jellyfish, as they are commonly called, are usually belled or saucer shaped with tentacle, which trail behind them. Some are opaque in appearance and other are transparent with the exception of internal body parts. The tentacle arms are attached to the rim of the bell and trail behind the organism. The jellyfish tentacles contain nematocysts with which are used to immobilize prey.

The most common medusa in coastal waters is the Cabbage Head or Stomolophus meleagris, The Cabbage Head enters into bays and estuaries during the summer months. Large numbers will wash up on the beaches providing food for tidal organisms. The Cabbage Head is a filter feeder. It has nematocysts, which are too weak to harm man.

Another jellyfish, which is common to bays and estuaries, is the Moon Jellyfish or Aurelia aurita. This is a plankton feeder. Aurelia has a shallow bell fringed with numerous very short tentacles and it has four short unfused arms. The four lobes of its stomach are often visible through the bell. Moon Jellies appears in swarms during the late summer or early autumn months.

The Hydromedusa, Nemopsis bachei, is a small transparent jellyfish, which appears in the winter and spring. Hydromedusa is only 1 cm in length and quite often over looked. It has a definite bell shape. There are four radical canals, which are clearly visible. A cluster of oral tentacles is suspended form the radical canals.

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