Identification Photos: Spiny Sand Star, Astropecten armatus: The Spiny Sand Star is a large, flattened sand star characterized by its red coloration which turns to brown and dark brown upon stress, the shape of its feet, and the location of its collection.

The Spiny Sand Star resides, half buried in sand within the low intertidal zone up to 180 feet deep in the water column. When disturbed, it will burrow under the sand. When placed on a solid surface, it will wander around looking for sand.

The Spiny Sand Star has small points on the end of its many feet, which are highly modified to allow it to glide and “scoot” over the bottom with great agility and relative speed. When placed upside down, it rights itself with an acrobatic flip. When stacked upon one another, Spiny Sand Stars quickly move apart.

The Spiny Sand Star has five arms and a maximum “wingspan” of 8 inches. It feeds primarily on the Olive Snail, Olivella biplicata, and has been known to consume at least one per day, but it also consumes dead fish, sea pansies, and sand dollars.

The Spiny Sand Star is present in all Mexican waters and is probably the most abundant of the sand stars at scuba depths in Southern California.

The Spiny Sand Star is an echinoderm and member of the Asteroidea Class and the Astropectinidae Family. The sand stars are very similar to the common starfish (they are collectively known as sea stars) but have small points on the ends of their many feet which give them great mobility over sand substrate. The echinoderms are a phylum of marine animals which include brittle stars, sea cucumbers, sea lilies, sand stars, starfish, and urchins. They are of great scientific interest because, via fossil records, they date to the Cambrian Age over 500 million years ago with 7,000 living species and 13,000 extinct ones.

Globally there are approximately 1,500 known species of sea stars, which are predominately found in intertidal zones but are also at depths of up to 30,000 feet. All have a central disc that merges gradually with the arms. Most have five arms, but some have more in a multiple of five. They all have radial symmetry. The bodies are flattened, flexible, and covered with a pigmented epidermis. Sand stars and starfish have a unique water-vascular system which uses hydraulic power to operate a multitude of tiny tube feet that are used in locomotion and food capture. Some feed via extruding the stomach out through the mouth, surrounding the prey, secreting enzymes to digest the food, and then retracting the stomach when they have finished eating. They are important predators within the ecosystem, feeding primarily on mollusks. They reproduce externally via egg and sperm release into the water.

Spiny Sand Star, Astropecten armatus: Donated to Mexfish.com by Mexican commercial pangueros, June 2007. Size, approximately 6 inches. Identification courtesy of Dr. Michel E. Hendrickx, Unidad Academica Mazatlan. Description and photos courtesy of John Snow.