Spiny Sand Star
Astropecten armatus

Physical Description

  • A small, flattened starfish, which grows to a diameter of about 7 inches
  • The center disc is quite small and the five arms are slender and pointed, slightly turned up at the tips
  • Margins of disk and arms are lined with spines and obvious plates
  • Colors on top, or back, can range from white to gray to dull pink to yellow-brown to lavender to match the substrate
  • Colors on bottom, or belly, are light yellow or ivory
  • Different species of the Astropecten genus are identified by patterns in the spines on the edges of their arms
  • Juveniles have stubbier arms than adults.

Range

  • Found in the eastern Pacific Ocean off of Mexico
  • From San Pedro, California to Ecuador

Habitat

  • Live in sandy or soft gravel seabeds, often hidden in the sediment
  • Found in sandy patches near reefs
  • Found at depths of 0 to 525 feet

Reproduction

  • Larvae of seastars are bilaterially symmetric, meaning they are symmetrical along one line. As the larvae grow up into juvenile spiny sea stars, they become pentaradially symmetric, meaning they are symmetrical along five lines.

Diet

  • Primarily feeds on the olive snail (Olivella biplicata)
  • Also eats sand dollars, sea pens, sea pansies (Renilla reniformis), sea urchins, and scavenges on dead fish 

Predators

  • Sea gulls and crabs often eat intertidal sea stars, though predators of spiny sand stars are unknown

Interesting Facts

  • This species is an agile sea star and can move quickly. It can “glide” across the surface of the sand with its mobile tube feet.
  • They do not have suckers on their tube feet like other sea stars, but instead have small points on the ends that can be used to bury themselves in the sand.
  • If turned upside down it can right itself with a flip. If several are stacked on top of each other, they will quickly disperse.

Sources: Monterey Bay Aquarium; Intertidal Invertebrates of California (p. 119); Mexican-Fish.com; MarineLifePhotography; Reeflex; Sea Stars of the Pacific Northwest; Invertebrate Zoology

Photo: Derek Tarr

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