Protoreaster nodosus (Linnaeus, 1758) (size not recorded)

Featured Invertebrate Data


Frequency on Okinawa: Collection Data (not collected)
[brackets indicate range for all Okinawa-collected/photographed specimens of the species]

Species Account:

        Protoreaster nodosus is considered to be relatively common in the waters of Okinawa's main island as well as in numerous areas of the warm, shallow waters of the Indo-Pacific region. Although no specimens were collected, numerous animals were seen, typically in shallow sand-bottomed seagrass bed environments. There are several common names associated with this attractive asteroid, "Chocolate Chip Starfish", "Horned Starfish", "Nodular Starfish", to name a few. "Chocolate Chip Starfish" is perhaps the most suitable.

        The following is paraphrased from Encyclopedia of Life(EOL):

The horned sea star (Protoreaster nodosus) is a relatively large Indo-Pacific asteroid which is commonly encountered in relatively shallow waters. It primarily inhabits seagrass meadows in the triangle formed by the Seychelles, New Caledonia, and southern Japan.

Colour in life: tubercles yellow with orange tips, papular areas blue-grey with paulae green; remainder of aboral surface deep green, marginals pale yellow, ambulacral spines white, tube feet pink with purple centre, adoral side purple with white plates showing through. Also distributed in Guam, Seleo Island, New Caledonia; Ceylon, East Indies, north Australia, Philippine, China, south Japan and South Pacific Is.; Australia. Ecology: benthic, inshore. General distribution: tropical, Indo-west-central Pacific Ocean, depth range 0-30 m.

        Additionally, the following is from Wikipedia:        

Protoreaster nodosus possess 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 are used to scare away 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 to the end, although there are anomalies like four or six-armed specimens; they may grow up to 30 cm (12 in) in diameter. The sea stars are usually colored in shades of red or brown, but can be light tan, the color of cookie dough. This appearance, combined with the small horns on its dorsal side, give the sea star a look similar to that of a bumpy cookie.

Habitat and behavior
Horned sea stars prefer sheltered, sandy or slightly muddy bottoms more than hard substrata such as coral reef, and are frequently sighted conspicuously 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. They do not withstand rapid changes well, however, and usually keep themselves underwater. 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. In this same setting, they will hunt down snails and eat them. An individual of horned sea star also has been observed eating a sea urchin in their natural habitat.

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 that would dare to eat this echinoderm.

        As one might guess, there are numerous photographs of this relatively large and fairly common starfish found on several on-line sites. Some of these locations are:

                Several pages of pix on Encyclopedia of Life(EOL)
                Numerous pix via Google
                Wild Singapore Fact Sheets

        In addition, there's an excellent article found on Chris Mah's Echinoblog in re conservation involving Protoreaster nodosus.


Literature Cited: