Sea Urchins of the Toxopneustidae Family, the globular Toxopneustid Sea Urchins, like Starfish and Sea Cucumbers are in the Phylum Echinodermata.

Echinoderms (meaning spiny skin) are characterized by a larval stage with bilateral symmetry and an adult stage with radial (5-rayed) symmetry. They are unsegmented. They may be disc, star, sphere, or cucumber-shaped. They have a water vascular system, tube feet, and a complete digestive system, but they lack a head, eyes, nervous system, or excretory system. They are found only in marine environments.

Toxopneustid Sea Urchins are in the Order Camarodonta, indicative that they have an internal skeleton (test) made of overlapping plates (ossicles). The test is disk shaped for irregular urchins (sand dollars), and globular for regular urchins (sea urchins). They lack the arms of sea stars, but are covered by movable spines. There are tiny pincers (pedicellariae) located between the spines. Their mouth is located on the flat, or concave, underside. Inside the mouth is a complex chewing apparatus, made of 5 jaws, that is known as an Aristotle’s Lantern. They move by the use of tube feet and by moving their spines. Differences in the construction of the test and lantern distinguish this Order of Sea Urchins from other Orders. Most of these differences are not distinguishable in the field. The most notable characteristic for Sea Urchins in this Family is a peristome (opening in the test) with sharp margins, and prominent buccal or oral cavity notches (that are difficult to observe in the field) and short to very short spines.

Sea Urchins of the Toxopneustidae Family are found in a variety of colors including black, blue, green, orange, pink and green. They are normally found on coral, rock or sand substrate at depths up to 100 m (328 feet). They have test diameters that can exceed 15 cm (5.9 inches). The Toxopneustidae Sea Urchins may be herbivorous grazers or depositional omnivores. They feed on algae, detritus and sea grasses. In turn they are preyed upon by fish, gastropods and sea stars. They utilize toxic venom for defense that is found within their globiferous pedicellariae which has a head with three moveable jaws. Each jaw has a sharp tooth with a venom sac at its base. Another unusual adaptation in this Family is the attaching of foreign objects on to the top (arboral) surface of the test. These species use their pedicellariae to pick up, and hold onto, pieces of algae, coral rubble, human rubbish or shell fragments. These objects may help to provide camouflage, armor, or sun protection for the urchin. Some species cover less of the body as they move deep in the water column that supports the idea that the objects provide sun protection. Like other Sea Urchins, the Toxopneustid reproduce sexually, with fertilization taking place externally.

The Toxopneustid Sea Urchins are distributed worldwide in tropical and sub-tropical seas. There are 35 species in the Toxopneustidae Family of which 3 species are found along Mexico’s Pacific Coast.

A Word of Caution!  The majority of Sea Urchins of the Toxopneustidae Family are not venomous or their pedicellariae is too small to access human skin. There are a few exceptions.  Multiple stings from some malo hombres may result in severe pain nausea, weakness, fainting, paralysis, and death. One should handle these urchins with care.