Acanthaster

Acanthaster is a genus of large, tropical starfish in the family Acanthasteridae. It includes the well known crown-of-thorns starfish (Acanthaster planci) and the short-spined crown-of-thorns starfish (Acanthaster brevispinus). Some taxonomic treatments recognize additional species, while others treat Acanthaster as a single variable species with regional forms.

Etymology and classification: The name Acanthaster derives from Greek, with acantha meaning spine and aster meaning star. Members are sea stars (echinoderms) in the order Valvatida. They are distinguished by numerous long spines that cover the body and are venomous to touch.

Description: Acanthaster species are robust, with a conspicuous array of long, conical spines on their upper surfaces. Spines are often brightly colored and can be venomous. The underside bears multiple tube feet used for locomotion and feeding. Coloration is highly variable, ranging from purples and pinks to browns and reds depending on species and environment.

Distribution and habitat: These starfish are native to the Indo-Pacific region, from the eastern Africa and the Red Sea across the Indian Ocean to the central Pacific. They inhabit coral reefs and reef flats, typically at shallow to mid-depths where corals are abundant.

Ecology and feeding: Acanthaster species are corallivores, feeding primarily on reef-building corals. They extrude their stomachs to digest prey externally and then absorb nutrients back into their bodies. Reproduction is typically sexual with broadcast spawning; eggs and sperm are released into the water, producing planktonic larvae and enabling wide dispersal.

Impact and management: Outbreaks can lead to rapid coral mortality and altered reef structure, making management a focus in affected regions. Natural predators such as the giant triton snail can help limit populations, while human impacts and nutrient enrichment can contribute to outbreaks. Control programs often involve monitoring and removal by divers, with ongoing research into effective management strategies.