Protoreaster nodosus

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Horned Sea Star

Scientific classification

Kingdom:	Animalia
Phylum:	Echinodermata
Class:	Asteroidea
Order:	Valvatida
Family:	Oreasteridae
Genus:	Protoreaster
Species:	P. nodosus

Binomial name

Protoreaster nodosus
(Linnaeus, 1758)

Protoreaster nodosus is a species of starfish found in the warm, shallow waters of Indo-Pacific region. Also known as "horned sea stars", they possess rows of spines or "horns"; black conical spines arranged in a single row, radially on the dorsal side, which may erode and becoming blunt. On the ventral side, tube feet, purple in color, are arranged in doube rows on each arms. Most horned sea stars found are roughly rigid five-pointed star-shape with tapering arms to the end, although there are anomalies like four or six-armed specimens; they may grow up to 30 centimetres in diameter. Usually colored in shades of red or brown, horned sea stars prefer sheltered, sandy or slightly muddy bottoms more than hard substrata such as coral reef, and frequently sighted conspicouously between the leaves of seagrasses on sea grass meadows or on blank stretch of coral sand. In shallow water, this species can be seen intertidally, occasionally exposed to the low tide. Sometimes, many individuals of this species can be seen gathering on soft bottom with reason not very well known, probably to increase the chance of fertilization when spawning or simply a suitable feeding ground.

Horned sea stars seem to be opportunistic carnivores; adults are known to predate on most sessile life forms including hard corals and sponges in aquarium; An individual of horned sea star is also has been observed eating a sea urchin in their natural habitat ^[1]. In public aquariums, these stars are sometimes target-fed with chopped squids, clams or shrimps, and are popular animals for touch pools as it is moderately large in number in some undisturbed areas. Horned sea stars need perfect water condition, suitable diet and proper acclimatization to thrive - thus, these sea stars did not fare very well caused by several factors mentioned before in many home aquariums. In reef aquariums, they are regarded as undesirable as they have destructive tendencies of toppling decors and digesting patches of corals and sessile organisms; they are reasonably safe if kept in a fish-only aquarium.

In many tropical Asian and Pacific countries, horned sea stars are collected for sea shell trade for their ornate skeletons. In some areas overharvesting is an issue and reduces greatly the population of the echinoderms. Related to this species, the Atlantic Oreaster reticulatus or commonly known as Bahama Sea Star, is also a previously-abundant species reduced in number due to the continuous harvesting by the industry and tourists alike.

As with other tropical echinoderms, commensal animals like shrimps (of genus Periclimenes), tiny brittle stars and even juvenile filefish can be found on the surfaces of a horned sea star. This may be attributed to its protective nature, as there are few predators would dare to eat this echinoderm.