Crown-of-thorns starfish

The Crown-of-thorns starfish (Acanthaster planci) is a large starfish, reaching up to 60 cm in diameter. It has numerous long, pointed arms, typically ranging from 12 to 19, covered in venomous spines. The spines cover both the upper and lower surfaces of the arms and body. Its color varies from red and purple to green and brown, which helps this starfish camouflage itself among corals.

The Crown-of-thorns starfish inhabits the tropical and subtropical waters of the Indo-Pacific, from the Red Sea to Central America. It prefers coral reefs at depths ranging from 1 to 30 meters, but is occasionally found at greater depths.

The Crown-of-thorns starfish is a corallivore. Its primary food source is hard corals (scleractinians), which it digests externally: by everting its stomach, it releases enzymes that break down coral tissue. This can lead to significant destruction of coral reefs, especially during population outbreaks.

Reproduction in the Crown-of-thorns starfish occurs through spawning. Females can produce up to 60 million eggs in a single spawning event. Eggs and sperm are released into the water, where external fertilization takes place. The larvae develop in the plankton and, after several weeks, settle on the seabed, transforming into juvenile starfish.

The Crown-of-thorns starfish poses a danger to divers due to its venomous spines. Contact with the spines can cause severe pain, swelling, nausea, and even paralysis. Wounds from the spines can take a very long time to heal and are susceptible to infection.