The blue glaucus, or Glaucus atlanticus, is a striking marine creature. This small sea slug measures around 1.2 inches (3 cm) and features iridescent blue and silver coloration, aiding camouflage. Often referred to as “blue dragon,” “sea swallow,” or “blue angel,” it possesses a flattened body with six unique, finger-like appendages. Despite its delicate appearance, this animal carries a potent defense mechanism.
The Sting’s Severity
While the blue glaucus is unlikely to cause fatalities, it can deliver a painful sting. This sea slug obtains its defensive capabilities by preying on other venomous marine organisms, most notably the Portuguese Man O’ War. The blue glaucus is immune to its prey’s venom, storing stinging cells (nematocysts) in specialized sacs at the tips of its cerata. By concentrating these ingested stinging cells, the blue glaucus can deliver a more potent sting than the creature it consumed.
Symptoms commonly include intense localized pain, nausea, vomiting, skin rashes, numbness, redness, papules, and fluid-filled blisters. While most reactions are not life-threatening, severe allergic reactions or systemic effects, though uncommon, are possible. While death is extremely rare, a severe reaction could pose a serious threat.
What to Do if Stung
Immediate first aid is important for a blue glaucus sting. Carefully remove any visible stinging cells from the affected area using tweezers or a bank card edge, avoiding bare hands to prevent further envenomation. Rinse the stung area thoroughly with seawater; avoid fresh water, which can cause remaining nematocysts to discharge more venom.
Applying heat to the affected area can help alleviate pain and denature the venom. Soak the area in very warm water (around 45°C) for 20 to 90 minutes. If soaking is not possible, use hot flannels or towels. Seeking medical attention is advisable if symptoms are severe, persist, or if an allergic reaction, such as difficulty breathing or widespread swelling, is suspected.
Where They Are Found and How to Avoid Them
Blue glaucus sea slugs are pelagic, living in the open ocean, primarily in tropical and temperate waters across the Atlantic, Pacific, and Indian Oceans. They float upside down at the surface, using a gas-filled sac in their stomach for buoyancy and relying on ocean currents and winds for movement. These sea slugs frequently wash ashore, especially after strong winds or storms, often forming groups known as “blue fleets.”
Exercise caution if you see these creatures on a beach. Even if they appear dead or washed ashore, their stinging cells remain active and can deliver a painful sting. Their small size and attractive appearance can make them tempting to pick up, but never touch them. Observe them from a distance to ensure safety and avoid stings.