Starfish, often called sea stars, cannot “sting” like a jellyfish. Unlike cnidarians, which use specialized stinging cells, starfish are echinoderms, a group that includes sea urchins and sea cucumbers. These marine invertebrates lack any venom-injecting apparatus to actively sting or bite humans. While most species are harmless, they do use defense mechanisms that can cause irritation upon contact.
Starfish Anatomy and Physical Defenses
The firm, rough exterior of a starfish is a primary physical defense. Its skeleton consists of calcareous plates called ossicles embedded in the body wall. Many species feature fixed or movable spines that act as a physical barrier against predators. These spines vary in sharpness and length but are mechanical deterrents, not tools for venom delivery.
Many starfish also have thousands of tiny, movable, pincer-like structures called pedicellariae scattered across their body surface. These appendages look like miniature jaws on stalks and are used to keep the animal free from debris, parasites, and settling organisms. In some species, pedicellariae can snap shut to discourage small attackers. Although they can clamp onto a person’s skin, they are non-toxic and their action is a reflex response to contact.
Chemical Toxicity and Species to Avoid
While the typical starfish is safe to handle, some species can cause envenomation through physical injury. The Crown-of-Thorns starfish (Acanthaster planci) is venomous because its spines introduce toxins upon puncture. These long, sharp spines are coated in a mucous layer containing potent toxins, such as asterosaponins and plancitoxins.
When a spine pierces the skin, the toxins are released into the wound, causing immediate, sharp, burning pain. The saponins have a hemolytic effect that can cause persistent bleeding, intense swelling, and localized tissue damage. Contact may also lead to systemic symptoms like nausea and vomiting, which can last for several hours or even days.
Safe Handling and Observation
The best practice when encountering any marine life, including starfish, is observation without contact. If interaction is unavoidable, remember that starfish are delicate organisms that breathe through tiny gill-like structures called papulae. Lifting a starfish completely out of the water causes these structures to dry out rapidly. Air can also enter their internal water vascular system, causing significant internal damage and stress.
If handling is necessary, ensure your hands are wet and free of substances like sunscreen, which can be toxic to the animal. Hold the animal gently, fully submerged, and return it to its original location quickly to minimize stress and potential harm. If contact with a known toxic species occurs and results in severe pain, extensive swelling, or systemic reactions, seek medical attention promptly, as embedded spine fragments may also need removal.