Moon jellies are common, translucent marine creatures frequently encountered in coastal waters worldwide. These invertebrates raise a common question for swimmers and beachgoers: do they sting? This article addresses their sting, what to do if contact occurs, and identification.
Understanding the Moon Jelly Sting
Moon jellies possess stinging capabilities, but their sting is generally considered very mild and not dangerous to humans. Rather than long tentacles, moon jellies have short, fine tentacles lining the bell’s margin. These tentacles are equipped with specialized stinging cells called nematocysts, which contain venom. When triggered by touch, these tiny, spring-loaded structures fire, injecting venom into the skin.
The sensation of a moon jelly sting is typically described as a mild prickle, itch, or tingling. Most people experience only a slight reaction, if any, and symptoms are usually transient. Common, temporary symptoms can include mild redness or slight irritation at the site of contact. While the venom can cause localized effects, it is not strong enough to penetrate human skin deeply, resulting in a minor stinging sensation.
What to Do After a Moon Jelly Sting
If you experience a moon jelly sting, the immediate response can help alleviate discomfort. Begin by rinsing the affected area with seawater to wash away any remaining tentacles and venom. Avoid using freshwater, as this can sometimes trigger more nematocysts to fire.
After rinsing, gently remove any visible tentacles from the skin using tweezers or a gloved hand. Do not rub the area, as this can release more venom from any remaining stinging cells. Applying a cold compress or immersing the area in cold water can help reduce pain and swelling. Some sources also suggest immersing the area in hot water (around 110 to 113°F or 43 to 45°C) for 20 to 45 minutes to help neutralize the venom and alleviate pain.
Spotting a Moon Jelly
Identifying moon jellies helps you appreciate them from a safe distance or avoid contact. They are easily recognized by their translucent, disc-shaped bell, which can appear clear or have a slightly bluish or pinkish tint. A distinctive feature is the presence of four horseshoe-shaped gonads, which are often visible through the top of their bell and can be pinkish or purple.
The bell of a moon jelly typically ranges in size, up to 12 to 24 inches (30 to 60 cm) in diameter, similar to a dinner plate. Moon jellies have short, fine tentacles that fringe the edge of their bell. They are commonly found in coastal waters, estuaries, and harbors, often floating just below the surface, and can sometimes be seen in large groups.