Field Guide to Venomous and Medically Important Invertebrates ...

The lion’s mane jellyfish, Cyanea capillata, is a large species distributed in the North Atlantic
Ocean and Artic Sea that can deliver a powerfully painful sting. This jellyfish can grow up to
6.5 feet (2 meters) in diameter and they have long stinging tentacles. Their sting causes severe
burning and blistering. Prolonged stinging events can cause muscle cramps and respiratory
distress, and can be fatal in some cases.
Figure 238. Lion’s mane jellyfish (Cyanea capillata). Photo: New York Aquarium.
Portuguese Man O’War
Portuguese Man O’War (Physalia physalis), is a large hydroid jellyfish characterized by a large
bluish gas filled sac (pneumatophore) that acts like a sail to drive the animals though the water
and often towards shore. Their long tentacles reach up to 10m in length and are responsible for
stings causing severe pain followed by a dull ache that involves the joints. The sting site
develops a red line with white lesions that may resemble a ladder-like pattern, and small wheals
may develop that resemble a string of beads. A systemic syndrome lasts for up to 24 hours and
comprises hypotension (sometimes shock), abnormally fast heart beat, chills, muscle cramps,
nausea and vomiting, irritability and confusion. Deaths have been reported from respiratory
failure. Treatment is mainly supportive but may require advanced life support measures in some
cases. Local corticosteroid creams may reduce inflammation. Patients should be hospitalized
and possibly admitted to intensive care depending on the severity of the systemic syndrome.
Figure 239. Portuguese Man O’War (Physalia physalis). Photo: NOAA.
Sea Anemones