Grooved Heart Urchin, Agassizia scrobiculata
Grooved Heart Urchin, Agassizia scrobiculata. Urchin collected off the beach at Punta Chivato, Baja California Sur, February 2023. Size: 2.8 cm (1.1 inches) x 2.5 cm (1.0 inch) x 2.2 cm (0.9 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.
Grooved Heart Urchin, Agassizia scrobiculata. Urchin collected off the beach at Punta Chivato, Baja California Sur, February 2023. Size: 3.3 cm (1.3 inches) x 3.1 cm (1.2 inches) x 2.0 cm (0.8 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.
Grooved Heart Urchin, Agassizia scrobiculata. Urchin provided the commercial fishermen of the greater Los Cabos area, June 2015. Size: 15.0 cm (5.9 inches) x 13.4 cm (5.3 inches). Identification courtesy of Bob Hillis, Ivins, Utah.
Grooved Heart Urchin, Agassizia scrobiculata. Collected off the beach of Bahía Concepción, Baja California Sur, March 2020. Collection and photographs courtesy of Barry Mastro, Escondido, California.
Phylogeny: The Grooved Heart Urchin, Agassizia scrobiculata (Valenciennes, 1846), is a member of the Prenasteridae Family of Heart Urchins. Heart Urchins derive their name from their heart-shaped test (skeleton). The Agassizia genus is one of three genera in the Prenasteridae Family, and there are two species in the Agassizia genus. This genus is named after Alexander Agassiz, the son of the more famous biologist Louis Agassiz. The species name scrobiculata comes from the Latin words meaning ” having small, shallow grooves or pits”. This refers to the prominent ambulacral grooves found in this species. Grooved Heart Urchins are known in Mexico as Erizo Corazón Surcado and Galleta de Mar.
Morphology: Grooved Heart Urchins are irregular urchins in that they are not radially symmetrical like regular urchins, instead they are bilaterally symmetrical. Their body has a somewhat elongated oval outline, though this species has a more round, inflated shape than other heart urchins in the region. Their mouth is placed towards one end of the animal, and the anus towards the other. These tests are flat on the oral surface (bottom) and rounded on top. Grooved Heart Urchins have short spines covering their tests. The spines are used for movement, including helping the urchin burrow into the sand. Heart urchins have tube feet that extend from petal-shaped grooves in their test called ambulacral grooves. The tube feet are used for respiration, movement, and feeding. The ambulacral grooves are quite pronounced on both the top and bottom surfaces. They vary in color from white to brown. Grooved Heart Urchins reach a maximum of 5.6 cm (2.2 inches) in length.
Habitat and Distribution: Grooved Heart Urchins are found on and under sand and mud, and sometimes under rocks. They live in the intertidal zone, and to depths up to 220 m (722 feet). The Grooved Heart Urchin is a subtropical to tropical Eastern Pacific species. In Mexican waters they range from Magdalena Bay, Baja California Sur, to Guatemala. They are found throughout the Gulf of California.
Diet: Grooved Heart Urchins are depositional feeders and detritivores. They use their tube feet to gather organic particles from the sediment and from the water around them. They also use their tube feet to pass the food to their mouth.
Predators: Grooved Heart Urchins are a poorly studied and understood species. There is no documentation regarding their predators. Other species in the Prenasteridae Family are preyed upon by fish and starfish.
Reproduction: Grooved Heart Urchins are gonochoric (male or female for life). They reproduce sexually through broadcast spawning, with external fertilization. The fertilized eggs hatch into planktonic larva. These larva eventually settle to the sea floor and develop into their adult form.
Ecosystem Interactions: Grooved Heart Urchins are a poorly studied and understood species. There is no documentation regarding their commensal, parasitic or symbiotic relationships.
Human Interactions: Grooved Heart Urchins 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: Agassizia ovulum and Agassizia subrotunda.