Black Spiny Brittle Star, Ophiocoma aethiops

Black Spiny Brittle Star, Ophiocoma aethiops. Brittle star collected from a tidal pool in the greater Los Cabos area, Baja California Sur, January 2016. Wing-span: 35 cm (14 inches).

Phylogeny: The Black Spiny Brittle Star, Ophiocoma aethiops (Lütken, 1859), is a member of the Ophiocomidae Family of Brittle Stars, that has two subfamilies, Ophiocominae and Ophiopsilinae that have four genera and one hundred twenty-seven species and one genera with thirty species, respectfully. The Ophiocoma Genus has seventy-seven known species. They are is also known as the Giant Black Brittle Star and in Mexico as Estrella Bailarina.

Morphology: The Black Spiny Brittle Star is the largest brittle star found in the Eastern Pacific. They have a round central disk that has a  scalloped margin and large oblong oral shields. The arms are rounded, stout and slightly flattened with three or four alternating spines that are as long as the diameter of the arms and stretch out perpendicularly to the arm axis. The aboral or dorsal surface of the disk has a uniform light brown coloration and is covered with minute granules. The dorsal side is dark brown in color and the ventral side lighter brown. They have arm lengths of up to 43 cm (17 inches) and the maximum central disk that is 3.7 cm (1.5 inches) in diameter.

Habitat and Distribution: The Black Spiny Brittle Star is common on rocky shores, under rocks in sand, or muddy areas of the lower and intertidal zones at depths up to 30 m (100 feet). They are a subtropical to tropical Eastern Pacific species. The Black Spiny Brittle Star is found in all Mexican waters of the Pacific Ocean and are exceedingly abundant in some locations.

Diet: Black Spiny Brittle Stars are opportunistic scavengers, deposit feeders, and suspension feeders. The use their bristly arms to sweep the water and the substrate to collect algae, diatoms, and detritus.

Predators: Black Spiny Brittle Stars are preyed upon by crabs, fish, crabs, and sea stars.

Reproduction: Black Spiny Brittle Stars are gonochoric (male or female for life). Reproduction is sexual, through broadcast spawning, with external fertilization. They are known to brood their fertilized eggs within their respiratory structures. The eggs hatch into planktonic larvae, which later metamorphose into juvenile brittle stars.

Ecosystem Interactions: The commensal, symbiotic, and parasitic relationships of Black Spiny Brittle Stars have not been documented.

Human Interactions: Black Spiny Brittle Stars have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: None