Mediterranean Box Jelly

Carybdea marsupialis is a small transparent jellyfish with a box-shaped bell about 3 cm (1 in) across, at the four lower corners of which are four elongated tentacles up to 30 cm (12 in) long. The bell has a number of small white or yellowish warts with stinging cells, and near the margin, equidistant from the tentacles, are four rhopalia (sensory structures with ocelli). This species can be distinguished from other similar species by the red banding on the tentacles.

Carybdea marsupialis was once considered a widespread species found in warm oceans around the world. Taxonomic reviews have shown that most of these are other species in the genus Carybdea, with the true C. marsupialis essentially restricted to the Mediterranean Sea. It is the only box jellyfish in this sea. It is pelagic and is present in the upper few metres of the sea.