Sea cucumbers, belonging to the class Holothuroidea, are marine invertebrates within the phylum Echinodermata, which also includes starfish and sea urchins. They generally appear as slow-moving, leathery-skinned, elongated creatures on the ocean floor, earning their common name from their resemblance to the vegetable. While their docile appearance suggests they are harmless, certain species possess potent defense mechanisms that can pose a danger, particularly when handled or consumed improperly. Most casual interactions are safe.
Chemical Danger From Sea Cucumber Toxins
The primary danger from certain sea cucumber species comes from a class of saponin-like toxins known as holothurins, which are concentrated in the body wall and specialized defensive organs. Holothurins are anionic surfactants that can disrupt cell membranes, leading to the lysis, or rupture, of red blood cells. The concentration of this toxin varies significantly depending on the species and the environment.
The most significant risk to humans involves ingestion, as consuming wild or improperly prepared sea cucumbers can be fatal. If ingested, the toxins can cause severe symptoms such as muscle cramps, stomach pain, and potentially death through respiratory paralysis. Many species are safely consumed as a delicacy, but this requires extensive preparation, such as boiling and gutting, to remove the holothurins. Commercial species are generally safe when sourced and prepared correctly.
Beyond ingestion, contact with the toxin can cause localized irritation. Handling certain sea cucumbers without gloves can lead to acute irritant dermatitis, characterized by swelling and marked redness of the skin. A more serious risk is contact with mucous membranes, as holothurins can cause painful chemical conjunctivitis if they enter the eyes. In severe or untreated cases, this exposure can result in blindness.
Startling, Non-Lethal Defenses
When stressed or attacked, many sea cucumbers employ physical defenses that are primarily startling rather than chemically toxic to humans. One such mechanism is evisceration, where the animal forcefully expels parts of its internal organs, typically through the anus. The ejected organs often include the digestive tract and the respiratory tree, which act as a distraction for a potential predator.
In many species, the respiratory tree is attached to clusters of fine, sticky threads called Cuvierian tubules. These tubules are ejected through the anus and rapidly expand, becoming intensely adhesive upon contact with water. The threads can entangle and immobilize small predators, allowing the sea cucumber to crawl away.
While the Cuvierian tubules in some species do contain holothurin toxin, their main threat to a human is their extreme stickiness and difficulty in removal. Evisceration is a form of self-amputation, or autotomy, and the sea cucumber can regenerate its lost internal structures over a period of weeks or months. These physical defenses are not life-threatening.
Safety Guidelines for Interaction
The safest approach for the public is to observe sea cucumbers without touching them, as rough handling can trigger their defense mechanisms. Avoid picking up or manipulating the animal, which can cause it to eviscerate or expel its toxic tubules. If interaction is necessary, such as for research or aquaculture, wearing protective gloves will prevent skin contact with any secreted toxins.
Never attempt to consume any wild sea cucumber without expert knowledge, as the varying toxicity between species makes improper preparation highly dangerous. If you accidentally come into contact with the sticky Cuvierian tubules or the animal’s body fluids, immediately rinse the affected area with seawater to dilute the toxin. Avoid using fresh water on a skin contact site, as this can sometimes increase the pain.
If the toxins or tubules contact the eyes, immediate and thorough rinsing with fresh water or a saline solution is necessary, and medical attention should be sought. For general skin irritation, applying vinegar or isopropyl alcohol may help to neutralize the toxin. For the average person, the risk from a casual encounter with a sea cucumber is minimal.