Cushion Sea Urchin, Astropyga pulvinata
Cushion Sea Urchin, Astropyga pulvinata. Urchin provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, June 2009. Diameter: 20 cm (4.0 inches).
Cushion Sea Urchin, Astropyga pulvinata. Underwater photograph taken in coastal waters off Puerto Vallarta, Jalisco, September 2021. Photograph courtesy of Kevin Erwin, Seattle, Washington.
Cushion Sea Urchin, Astropyga pulvinata. Underwater photographs taken in coastal waters of the greater Los Cabos area, Baja California Sur, May 2018. Photographs courtesy of Bob Hillis, Ivins, Utah.
Cushion Sea Urchin, Astropyga pulvinata. Underwater photographs taken in Zihuatanejo Bay, Guerrero, March 2018. Photographs courtesy of Ron Woheau, Zihuatanejo.
Cushion Sea Urchin, Astropyga pulvinata. Underwater photographs taken in Zihuatanejo Bay, Guerrero, March 2018. Photographs and identification courtesy of Maude Jette, Dive Zihuantanejo, www.Divezihuantanejo.com.
Phylogeny: The Cushion Sea Urchin, Astropyga pulvinata (Lamarck, 1816), is a member of the Diadematidae Family of Sea Urchins. Astropyga is one of seven genera in this Family and there are four species within this genus. This species is also known as the Crown Urchin or Pin Cushion Urchin and in Mexico it is known as erizo cojín.
Morphology: The Cushion Sea Urchin body can be black, brown, red or violet in color. They have a pattern of five pale triangle-shaped blotches that are bordered by small, bright, blue spots on the aboral surface. They have long, sharp, thin spines that they may be banded with white or mostly white. These urchins are light sensitive and can move their spines to point toward potential threats. The test is somewhat flattened and can be as large as 12 cm (4.7 inches) in diameter. The spines are of similar length as the test diameter.
Habitat and Distribution: The Cushion Sea Urchin are found on coral, mud, rock, and sand substrate. They reside at depths between 3 m (10 feet) and 90 m (275 feet). They are normally found as solitary individuals but also congregate groups of three hundred or more, apparently in response to nutrient rich upwelling. In Mexican waters the Cushion Sea Urchin is a found in all waters of the Pacific with the exception that they are absent from north of Magdalena Bay, Baja California Sur, along the central and northwest coasts of Baja.
Diet: Cushion Sea Urchins are thought to be grazers, feeding on algae, and deposit feeders, feeding on detritus. There is one documented case of a Cushion Sea Urchin in captivity predating another species of urchin. This is not thought to be normal behavior for individuals in the wild.
Predators: Cushion Sea Urchins are pray numerous fish including triggerfish.
Reproduction: Reproduction in Cushion Sea Urchins is gonochoric (either male or female for life). Fertilization takes place externally, with the female carrying the eggs on her peristome. After the eggs hatch, the larvae are planktonic for several months, before settling to the bottom.
Ecosystem Interactions: Small shrimps and crabs may be found living between the bases of the spines of Cushion Sea Urchins. These crustaceans gain protection from the urchin’s spines, and they may benefit the urchin by removing harmful plants and animals from the surface of the urchin.
Human Interactions: While not generally significant, the collection of Cushion Sea Urchins in order to sell their tests as souvenirs, may cause local extirpations. From a conservation perspective the Cushion Sea Urchin has not been formally evaluated however they have are common with a wide distribution and should be consider to be of Least Concern.
A Word of Caution! The Cushion Sea Urchin is not venomous, but should be handled with care because the spines are sharp, will break off in the skin, can be very painful to humans and are exceedingly difficult to remove.
Synonyms: Astropyga depressa, Astropyga dubia, Astropyga venusta, Cidnarites pulvinata, Diadema pulvinata, and Diadema pulvinatum.