Toxopneustidae Family of Sea Urchins
Three Sea Urchins of the Toxopneustidae Family can be found in this website:
Phylogeny: Sea urchins of the Toxopneustidae Family, like starfish and sea cucumbers, are in the phylum Echinodermata. They are in the class Echinoidea, the subclass Euechinoidea, the infraclass Carinacea, the subterclass Echinacea, the order Camarodonta, the infraorder Echinidea, and the superfamily Odontophora. The Toxopneustidae Family is one of three families in this superfamily. The Toxopneustidae Family contains eight genera and around thirty-five species. The name Toxopneustidae comes from the Greek words meaning “poison breath”, and refers to the venomous nature of some of these urchins. Sea Urchins in this family are also known as Flower Urchins and Toxopneustid Sea Urchins.
Morphology: Toxopneustid Sea Urchins have an internal skeleton (test) made of overlapping plates (ossicles). The test is globular and covered with short moveable spines. There are tiny pincers (pedicellariae) located between the spines. Each of the globiferous pedicellariae has a head with three moveable jaws. Each jaw has a sharp tooth with a venom sac at its base. Some species also use their pedicellariae to pick up, and hold onto, pieces of algae, coral rubble, human rubbish or shell fragments. They attach these foreign objects to the top (arboral) surface of the test. 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. 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 sea urchins in this order from other orders. Most of these differences are not distinguishable in the field. The most notable characteristic for Toxopneustid Sea Urchins 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. Like all Echinoderms, they are characterized by a larval stage with bilateral symmetry and an adult stage with radial (5-rayed) symmetry. They have a water vascular system and a complete digestive system, but they lack a head, eyes, nervous system, or excretory system. These Sea Urchins are found in a variety of colors including black, blue, green, orange, pink and green. They have test diameters that can exceed 15 cm (5.9 inches).
Habitat and Distribution: Toxopneustid Sea Urchins are normally found on coral, rock or sand substrates. They live from the intertidal zone to depths up to 100 m (328 feet). Toxopneustid Sea Urchins are distributed worldwide in tropical and sub-tropical seas. At least five species from this family are found in Mexican waters.
Reproduction: Toxopneustid Sea Urchins are gonochoric (either male or female for life). They reproduce sexually, through broadcast spawning, with external fertilization. The fertilized eggs develop into planktonic larvae before settling to the substrate to metamorphose into a juvenile sea urchin.
Ecosystem Roles: Toxopneustid 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. Some utilize toxic venom for defense that is found within their pedicellariae.
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 species may result in severe pain nausea, weakness, fainting, paralysis, and death. One should handle these urchins with care.