While the idea of a starfish being a deadly threat might seem like something from a science fiction movie, it’s a common query. Most starfish species are not dangerous to humans, but one notable exception exists. This article explores the general nature of starfish interactions, highlights the specific risks posed by the Crown-of-Thorns starfish, and provides guidance on how to respond to an encounter.
Understanding Starfish Interactions
Most of the approximately 1,900 species of starfish, also known as sea stars, pose no lethal threat to humans. These slow-moving bottom dwellers are found in all the world’s oceans, from tropical zones to polar regions. Many species possess a hard, spiny skin or an exoskeleton for defense against predators.
Starfish feed on benthic invertebrates like mollusks, often by everting their stomach onto their prey to digest it externally. Their primary defense mechanisms include camouflage, shedding limbs (autotomy) to escape predators, or producing unpalatable chemicals like saponins. While some starfish can produce slime or have mildly toxic chemicals in their body walls, these are not harmful to humans upon contact.
The Crown-of-Thorns Exception
The Crown-of-Thorns starfish ( Acanthaster planci) can cause considerable harm to humans. This large starfish, often reaching up to 50 cm in diameter, is named for the numerous sharp, venomous spines covering its upper surface. These spines, up to 4 cm long, are stiff and can easily pierce skin, delivering a potent venom.
Contact with the spines of a Crown-of-Thorns starfish results in immediate and severe stinging pain that can last for several hours. Other symptoms include localized swelling, redness, bleeding, nausea, vomiting, joint aches, and numbness or tingling. While extremely painful and requiring medical attention, a sting is rarely fatal to a healthy human, though severe cases can lead to systemic reactions like paralysis or, in rare instances, anaphylactic shock. The spines are brittle and may break off in the wound, necessitating surgical removal.
What to Do After an Encounter
When observing starfish, maintain a safe distance and avoid touching them, as even seemingly harmless species can be fragile or possess minor defenses. If a puncture wound occurs from a Crown-of-Thorns starfish, immediate first aid is necessary. Begin by immersing the affected area in water as hot as the injured person can tolerate (not exceeding 60°C or 140°F) for 30 to 90 minutes; this can help alleviate pain.
Carefully remove any visible spines from the wound using tweezers, taking care not to break them. Afterward, thoroughly scrub the wound with soap and water and rinse extensively with fresh water. Do not cover the wound with tape or an occlusive dressing, as this might increase infection risk. Seek professional medical attention if pain is severe, symptoms worsen, signs of infection (like increased redness, heat, or pus) appear, or if an allergic reaction occurs. A tetanus booster may also be recommended.