Diet

• Omnivorous and opportunistic feeder that scavenges detritus, organic particles, small invertebrates and other food material associated with the seafloor.

• Its long, flexible arms sweep food towards the mouth, allowing it to feed while remaining sheltered within reef crevices.

Range

• Tropical eastern Pacific, ranging from the Gulf of California and Pacific Mexico south through Central America to Colombia and Ecuador, including the Galápagos Islands.

• In Mexico it occurs from the Gulf of California southward along the Pacific coast.

• It is well represented in the Zihuatanejo area.

Habitat

• Found on rocky and coral reefs, sandy bottoms and other hard substrates, particularly in shallow water.

• Recorded from the intertidal zone to approximately 70 metres, although specimens from Mexican Pacific coral reefs in one study were collected between 2.3 and 26 metres.

• In the Zihuatanejo area it occurs on a variety of substrates, including rocks, sand, corals, sponges and hydrozoans.

• Juveniles can associate with hydrozoan colonies; a juvenile O. alexandri was reported living in association with a leptothecate hydrozoan in the eastern Pacific.

Description

• A large, robust brittle star with a relatively small, rounded disc and five very long, slender arms.

• The arms are proportionally longer than those of the closely related Ophiocoma aethiops, making O. alexandri particularly distinctive among the large brittle stars of the Mexican Pacific.

• The disc and arms are generally brown to dark brown, with contrasting markings that can vary among individuals.

• Arm spines are relatively large and stout, extending laterally from the arms and giving the animal a strongly spiny appearance.