Prickly Sea Star, Paulia horrida

Prickly Sea Star, Paulia horrida. Pictured stars wingspan: 13 cm (5.1 inches). Star courtesy of the commercial fishermen of Todos Santos, Baja California Sur, March 2013.  Exceedingly rare. Identification courtesy of Dr. Chris Mah, Smithsonian Institute, Washington, D.C.

Phylogeny:  The Prickly Sea Star, Paulia horrida (Gray, 1840), is a member of the Asterodiscididae family of Asterodiscid Sea Stars. The genus Paulia is one of five genera in this family. This is the only species in this genus. They are also known as the Horrida Spiny Sea Star and the Red Prickly Sea Star and in Mexico as Estrella de Mar Horrida. Paulia horrida var. galapagensis (Ludwig, 1905) is considered a valid variety within the species.

Morphology: Prickly Sea Stars have a wide central disk and five, short, tapering arms. The arms have a broad attachment point at the disk. There are two rows of tube feet, with suckers, on the underside of each arm. They have conspicuous ossicles (calcareous particles that are part of the endoskeleton) along their margins. The disk contains most of the organs, with the mouth on the ventral side and the anus and madreporite (entry plate for the water vascular system) on the dorsal surface. Numerous, sharp, conical spines cover the dorsal (aboral) and marginal surfaces of the disc and arms. They can be brown, orange, or vermillion in color, with bright orange spines. Prickly Sea Stars reach a maximum of  18 cm (7.1 inches) in diameter.

Habitat and Distribution:  Prickly Sea Stars are very rare, and little is known of their ecology. They are found on rocks and coral. They live at depths between 2 m (6 feet) and 123 m (403 feet), but in the northern portion of their range, they tend to have a more narrow depth range being found from 24 m (79 feet) to 91 m (298 feet). They are a tropical Eastern Pacific species that in Mexican waters are found from Magdalena Bay, Baja California Sur south to Guatemala.  They are also found in the Central and Southern Gulf of California and around the Revillagigedos and Tres Marias Islands.

Diet:  The Prickly Sea Stars are a poorly known species, with no records of its life cycle and ecology. Other species in this family feed on bivalves, crustaceans and gastropods.

Predators:  Prickly Sea Stars are rare and poorly studied. There is no documentation regarding predation for this species. Other species in this family are preyed upon by shore birds, crabs and fish.

Reproduction:  Prickly Sea Stars are gonochoric (male or female for life). They reproduce sexually through broadcast spawning, with external fertilization. The fertilized eggs hatch into planktonic larvae. The larvae start life in a bilaterally symmetrical form and in adulthood gain their radial symmetry. They are in their larval form for a few weeks before beginning their benthic life.

Ecosystem Interactions: There is no documentation of Prickly Sea Stars engaging in any types of commensal, parasitic, or symbiotic relationships.

Human Interactions:  Prickly Sea Stars have no direct impact on human activities. They are seldom seen by humans.  From a conservation perspective they have not been formally evaluated.

Synonyms:  Goniodiscus horridus and Nidorellia horrida.