Protoreaster nodosus

Lore & Background

Protoreaster nodosus possesses rows of spines or 'horns'—black conical points arranged in a single row radially on the dorsal side, which may erode and become blunt. These dark protrusions can intimidate possible predators by looking frightening or dangerous. On the ventral side, tube feet, purple in color (or pale, transparent pink), are arranged in rows on each arm. Most horned sea stars found are a roughly rigid five-pointed star-shape with tapering arms, although anomalies like four or six-armed specimens occur. The sea stars are usually colored in shades of red or brown, but can be light tan, resembling the color of cookie dough, which combined with the small horns gives an appearance similar to a chocolate chip cookie. Horned sea stars prefer sheltered, sandy or slightly muddy bottoms to hard substrata such as coral reefs or areas of vegetation like mangrove forests. They are frequently sighted between the leaves of seagrasses on sea grass meadows or on blank stretches of coral sand. Field studies suggest the species could be restricted to the western Pacific Ocean. In shallow water, this species can be seen intertidally, occasionally exposed to low tide. They do not withstand rapid changes well and usually keep themselves underwater. Many individuals can be seen gathering on soft ocean bottoms; the cause is mostly unknown, but it is thought to likely increase the chance of fertilization when spawning, or is simply a suitable feeding ground. Horned sea stars are opportunistic carnivores; adults are known to prey on most sessile life forms including hard corals and sponges in an aquarium, and will hunt down snails. An individual has been observed eating a sea urchin in their natural habitat. Commensal animals like shrimps (of genus Periclimenes), tiny brittle stars, and juvenile filefish can be found on the surface of a horned sea star, possibly attributed to its protective nature, as it has few predators.

Reader's Guide

Protoreaster nodosus is significant in the marine aquarium trade and as a dried curio, but overharvesting has had a severe impact on its population in many tropical Asian and Pacific countries where it is collected for the sea shell trade. The article notes that a related species, the Atlantic Oreaster reticulatus (Bahama Sea Star), is similarly a once-abundant species reduced in number due to continuous harvesting by both industry and tourists. The species' distinctive chocolate-chip-cookie appearance makes it a recognizable and sought-after echinoderm. Its ecological role as an opportunistic carnivore—preying on sessile life forms, snails, and even sea urchins—highlights its importance in benthic communities. The gathering behavior of many individuals on soft ocean bottoms, while not fully understood, is thought to relate to spawning or feeding. The presence of commensal animals on its surface underscores its role as a microhabitat. The article's reference to field studies suggesting a restricted range in the western Pacific Ocean indicates that conservation concerns may be geographically focused. The species' inability to withstand rapid changes and its preference for sheltered, soft-bottom habitats further inform its vulnerability to environmental disturbance and collection pressure.

Did You Know?

• The horned starfish's dark conical spines can intimidate predators by looking frightening or dangerous.
• Its coloration, combined with small horns, gives it an appearance similar to a chocolate chip cookie.
• Horned sea stars are opportunistic carnivores that prey on hard corals, sponges, snails, and even sea urchins.