Van Brunt’s Sea Urchin, Echinometra vanbrunti

Van Brunt’s Sea Urchin, Echinometra vanbrunti. Sea urchin collected from a tidal pool in the greater Los Cabos area, Baja California Sur, January 2010. Pictured urchin: 5.3 cm (2.1 inches).

Van Brunt’s Sea Urchin, Echinometra vanbrunti. Underwater photograph taken with coastal waters within Parque National Huatulco, Huatulco, Oaxaca, March 2021.  Photograph courtesy of Marina Sutormina, Stockholm, Sweden.

Phylogeny: Van Brunt’s Sea Urchin, Echinometra vanbrunti (A. Agassiz, 1863), is a member of the Echinometridae Family of Sea Urchins.  The genus Echinometra is one of nine genera in this family. There are six accepted species in this genus and four temporary members, pending further research.   This species is also known as the Central American Rock-boring Urchin, the Eastern Pacific Rock-boring Urchin and the Purple Sea Urchin. In Mexico it is called erizo de Van Brunt. They are the most abundant Sea Urchin in Mexican waters of the Pacific Ocean.

Morphology: Van Brunt’s Sea Urchin has a test that is slightly flatter than most other sea urchins in the area. Their spines are moderately long and taper to a sharp point. The spines and body are dark purple to black in color. Van Brunt’s Sea Urchins have a maximum test diameter of 7.0 cm (2.75 inches) and spine lengths of up to 6.3 cm (2.5 inches). Van Brunt’s Sea Urchin is sometimes confused with the Purple Urchin, Strongylocentrotus purpuratus (shorter spines, lighter purple color).

Habitat and Distribution:   The Van Brunt’s Sea Urchin is normally found attached to rocks, but on occasion can be found on sand substrate, in the intertidal zone to depths up to 53 m (175 feet). They are a rock-boring species, digging and occupying a cavity in the rock. In Mexican water’s Van Brunt’s Sea Urchin is found in all waters of the Pacific with the exception that are absent from Magdalena Bay, Baja California Sur, northward along the central and northwest coasts of Baja.

Diet:   Van Brunt’s Sea Urchins are benthic grazers, feeding on algae, and to a lesser extent, they are detritivores.

Predators:   Van Brunt’s Sea Urchins are preyed upon by sea stars and fish, such as wrasse and the Finescale Triggerfish, Balistes polylepis.

Reproduction: Van Brunt’s Sea Urchins are gonochoric (male or female for life).  Reproduction is sexual and fertilization is external. Brooding is common, eggs are held either on the peristome, around the periproct or deep into the concavities on the petaloids.  The embryos develop into planktonic larvae. The larva pass through different stages, over several months, before they sink to the bottom and metamorphose into young urchins.

Ecosystem Interactions:  The boreholes made by Van Brunt’s Sea Urchins are shared with several species of  blennies, brittle stars, clingfish, porcelain crabs, gobies, and shrimp. These animals gain protection by being in the hole with the urchin and the urchin does not appear to be harmed by their presence. The urchins themselves also host epibiotic species including shrimp and crabs.

Human Interactions:  Van Brunt’s Sea Urchins have limited direct impact on modern human activities. Complete animals of this species have been found in archaeological digs in central mainland Mexico and it is thought that they were used in religious ceremonies of the indigenous Aztecs.

A Word of Caution!  Van Brunt’s 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.

From a conservation perspective Van Brunt’s Sea Urchin has not been formally evaluated however they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.

Synonyms:  Echinometra macrostoma, Echinometra rupicola, Echinometra van brunti, Echinometra van-brunti, Ellipsechinus macrostomus, Heliocidaris stenopora, and Toxocidaris stenopora.