Brissidae Family of Heart Urchins

Two Heart Urchins of the Brissidae Family can be found in this website:

Phylogeny:  Heart Urchins of the Brissidae Family, like Basket Stars, Sea Cucumbers, Sea Stars, and Sea Urchins are in the phylum Echinodermata.  They are in the subphylum Echinozoa, the class Echinoidea, the subclass Euchinoidea, the infraclass Irregularia, the subterclass Atelostomata, the order Spatangoida, and the suborder Brissidina, which is one of two suborders in this order. The suborder Brissida contains one superfamily and nine families. The Brissidae Family consists of one subfamily, thirteen genera, and fifty-six species. The name Brissidae comes from the Greek words meaning “bristle”, and refers to the small spines found on these animals.

Morphology:  Brissidae Heart Urchins have an irregular profile with bilateral symmetry. They lack the radial symmetry of regular Sea 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). The exterior is covered with small 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. Generally, Heart Urchins are drably colored with most being gray, brown, greenish, or reddish. Heart Urchins reach a maximum of 20 cm (7.9 inches) in length.

Distribution:  Brissidae Heart Urchins are found in soft sediments including sand, mud, and gravel. They are usually buried with their front end pointing downward. They may burrow as deep as 20 cm (7.9 inches).  Brissidae 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. They are found worldwide, in tropical to temperate seas. Eight species of the Brissidae Family are found in Mexican waters.

Reproduction: Brissidae Heart Urchins are gonochoric (females or males 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.

Ecosystems Roles: Brissidae Heart Urchins consume organic particles found in the sediment and adjacent water. They use their tube feet to gather organic particles and to pass the food to their mouth. In turn they are preyed upon by fish and starfish. Their burrowing activities play an important role in breaking up bottom sediments to keep them from becoming hard-packed and less productive as habitat.