The Clinging jellyfish - a beautiful but invasive and dangerous species

Gonionemus vertens (Limnomedusae - Olindiidae) is a bell-shaped hydromedusa (not a true jellyfish) with about 60-80 unbranched tentacles evenly spaced around the margin of the bell. The tentacles have large rings of nematocysts (stinging cells to stun prey and defend against predators) all along their length, and partway back from the tip of each tentacle is a larger adhesive knob or pad used for attachment to eelgrass or macroalgae. 

This species occurs in the Pacific (from Alaska to southern California, Kamchatka, and northern Japan), the Arctic Ocean, and was introduced to the North Atlantic by 1894.

Gonionemus vertens may be spreading in Atlantic waters, and increasing in both numbers and in toxicity. In humans, multiple stings from clinging jellyfish can cause acute respiratory problems, joint pains, and acute dermatitis that can take days to heal.

In Japan, sensitive humans who come into contact with its stinging cells in that region may suffer severe allergic reactions, resulting in the worst cases in fatal anaphylactic shock.

Other common names: Orange-striped jellyfish, Angled hydromedusa.

References: [1] - [2]

Photo redit: ©Alexander Semenov | Locality: Japan Sea (2011)