Slender sea star, Astropecten spinulosus

The Slender sea star (Astropecten spinulosus), is a species of starfish in the Astropectinidae family. It is found only in the Mediterranean Sea, spending much of its life on sandy, muddy or gravelly seabed in areas very rich in algae from 3.5 to 165 feet deep. Its favorite seabed meadows are Mediterranean Tapeweed (Posidonia oceanica) and Little Neptune Grass (Cymodocea nodosa). The common name Sea Star is a generic term given to other members of this genus as well.

This sea star spends the day buried in sediment, emerging in the late afternoon and evening to go on the hunt for its primary food, bivalve mollusks. It is very active at night and is easy to spot. It catches prey with its arms and takes it to its mouth. The prey is trapped by long, moving prickles found around the mouth cavity.

This species has very short superomarginal plates completely covered by scales and very small spines. Most of the spines are so small that they are not considered spines at all; only 1 to 3 found on top of the plate are considered real spines. The color of the spines is similar to the plates — brown or clear-brown. Inferomarginal spines are long and pointed and are bluish-purple in color.

The arms of the slender sea star are sometimes rounded at the ends. The aboral side (away from the mouth) is a dark color: typically brown, reddish-brown, or greenish. It is the only member of its genus that often moves away from mobile seabed and into hard substrate, in caves, and even climbing on grassy surfaces.

This small starfish grows to just over 3 inches in diameter on average (maximum: 4 inches). It is distinguishable from other members of its genus by the short superomarginal plates, the color of its aboral side, and the color and size of its inferomarginal spines. However, it can often be confused with Astropecten platyacanthus.