Brissidae Family of Heart Urchins

Obese Heart Urchin, Brissius obesus. A representative of the Brissidae Family of Heart Urchins.

Phylogeny:  Heart Urchins of the Brissidae Family, like Basket Stars, Sea Cucumbers, Sea Stars, and Sea Urchins are in the Phylum Echinodermata. There are fifty-six species of the Brissidae Family of which six species are found along the Pacific Coast of Mexico. They are in the Class Echinoidea and the Order Spatangoida.

Distribution:  Brissidae Heart Urchins are found worldwide, in tropical and temperate oceans. They are found in soft sediments including sand, mud, and gravel usually buried with their front end pointing downward. They may burrow as deep as 20 cm (7.9 inches).  These Heart Urchins generally reside in shallow waters, at depths between 1 m (3 feet) to 48 m (160 feet). Since these are burrowing animals, heart urchins are not often seen alive, but their tests may wash ashore.

Morphology:  The Brissidae have an irregular profile with bilateral symmetry lacking the radial symmetry of regular Urchins. Their bodies have a somewhat elongated oval outline with mouths that are located towards one end of the animal, and the anus towards the other. They have heart shaped tests (skeletons) that are flat on the oral (bottom surface) and rounded on top (dorsal surface and covered with spines. The spines are utilized for movement, including helping the urchin burrow into the sand. Heart Urchins have tube feet that extend from petal-shaped (ambulacral) grooves in their test that are used for feeding, movement and respiration. Heart Urchins lack the complex mouth parts (Aristotle’s Lantern) found in regular urchins. Heart Urchins also have pedicellariae (minute pincers) that help deter predators. Some of these urchins can reach 20 cm (7.9 inches) in length.

Ecosystems Roles: Brissidae consume organic particles found in the sediment and adjacent water. In turn they are preyed upon by fish and starfish.