Some Sea Urchins Are Venomous, But Usually Not Very Dangerous

High Angle View Of Sea Urchins
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Open-water divers have a number of creatures to be concerned about, including a few that are venomous and are a legitimate cause for concern. Among the creatures that are venomous but don't pose all that great a danger are a few species of the many types sea urchins. Those with poisonous spines include the Echinothuridae, Toxopneustes, and Tripneustes species.

But don’t worry. A rabid sea urchin is not going to leap off the reef and fling spines at you. Sea urchins are non-aggressive and relatively slow-moving. Still, sea urchin injuries are not uncommon in scuba diving. Stings most often occur when a swimmer or a diver accidentally brushes against one of these delicate creatures, not because the urchins attack in any way. 

Sea Urchins Are Everywhere

Sea urchin injuries are common because sea urchins are common. Divers encounter sea urchins in almost everybody of saltwater, including all of the world’s oceans. Rocky shores and shallow, sandy areas are some of the sea urchin’s favorite habitats. Shore divers need to take care to avoid stepping on urchins when wading in shallow water.

Sea urchins are also found on coral reefs. Urchins hide in the reef’s crevices during the daytime, and at night, they wander out to feed on floating food particles and algae. While divers can occasionally find sea urchins during the day, they should be particularly careful during night dives not to accidentally touch urchins that are more exposed at feeding time.

Sea Urchins Have Two Defense Mechanisms

Like most aquatic life injuries, sea urchin injuries are the result of the animal trying to defend itself. A sea urchin’s spines are its first line of defense. The length and sharpness of an urchin’s spines vary from species to species. Some species have stubby, blunt spines, while other species have long, sharp, venom-filled spines. Razor-sharp spines can easily pierce even a thick wetsuit and lodge deep in a diver’s skin.

Many urchin species, such as the purple sea urchin, have an additional defense mechanism called the pedicellarines. The pedicellarines are tiny, jaw-like structures that can clasp onto a diver’s skin and inject a painful poison. They are nestled down between the urchin’s spines and are difficult for a diver to contact unless he has already impaled himself on the urchin’s spines.

In extreme cases, such as when a diver suffers numerous puncture wounds, the relatively small amount of venom from spines and pedicellarines can accumulate in sufficient quantities to cause severe muscle spasms, faintness, difficulty breathing, and death. 

Don't Touch the Urchins and You Will Be Fine

Avoiding sea urchins is sometimes easier said than done. Try to maintain good awareness of your surroundings. Control your buoyancy to stay at least a few feet from coral, which may conceal urchins in its crevices. Divers should also watch out for protruding spines in the sand, as many sea urchins bury themselves.

Most commonly, stings are the result of distracted diving, as when a diver charges after a turtle for a photo and inadvertently touches an urchin.

Sometimes conditions make it hard to see urchins and avoid touching them—for example, a rough shore entry through waves. Thick-soled diving booties, gloves, and thick wetsuits may provide some level of protection. But long and sharp spines may still be able to pierce thick neoprene. If a shore entry has many urchins, pick a different dive site.

First Aid for Sea Urchin Stings: No Peeing!

Contrary to what some believe, urinating on a sea urchin sting will not help, so save yourself the embarrassment (nor does it work as first aid for jellyfish stings). Because there are two sources of injury from sea urchins—the spines and the poisonous pedicellarines—you need to deal with both.

Spines: A sea urchin’s spines can inject painful venom. Soaking the area in hot water (110 to 130 F) for up to an hour and a half can break down the venom and help to alleviate the pain. Carefully remove the spines with tweezers, because the fragile spines may be crushed or broken while under the skin. If you cannot easily remove a spine or it is near a joint or close to delicate nerves and blood vessels in your hands or feet, it is best to have a doctor surgically remove it. Dark-colored spines dye the skin, so you will be able to identify the spot if a spine remains. This coloration should disappear within two days. If it doesn't, see a doctor to remove the spine.

Pedicellarines: Remove an urchin's pedicellarines by shaving the area with shaving cream and a razor. After removing the spines and pedicellarines, wash the injured area with soap and rinse with fresh water. Apply topical antibiotic creams, and take analgesics for the pain.

As with any aquatic life injury, watch for signs of infections or allergies, such as chest pain or difficulty breathing. Contact a doctor immediately if you observe either.

Among other sea creatures that pose a hazard to divers are bearded fireworms, pufferfish, fire coral, and stinging hydroids. But of the dangers of the deep, the meek sea urchin is a relatively tame one.