Leopard Sea Cucumber
Holothuria pardalis

Impatient Sea Cucumber
Holothuria impatiens

Sulfur Sea Cucumber
Selenkothuria lubrica

Sea Cucumbers of the Holothuriidae Family, like Starfish and Sea Urchins are in the Phylum Echinodermata. Echinoderms, indicative of spiny skin, are characterized by a larval stage with bilateral symmetry and an adult stage with radial (5-rayed) symmetry. They are unsegmented and their disc may be cucumber, sphere or star shaped. They have a water vascular system, tube feet, and a complete digestive system, but they lack eyes, a head, nervous system, or excretory system. They are found only in marine environments. Sea Cucumbers are in the Class Holothuroidae, meaning that they lack arms, and they have a soft body wall and branched tentacles around their mouth utilized to capture food. Sea Cucumbers are in the Order Holothuriidae, indicative that the tentacles around their mouth are flattened, and often leaf-like, their body wall is thick and leathery, with ossicles (tiny, calcified rods or tables under the skin) and their tube feet form a noticeable sole, and they may be spherical or elongate in shape. Sea Cucumbers in this order may have one of two unique defense mechanisms. Some species can shoot sticky white threads (Cuvierian tubules) out of their anus, which may entangle or distract predators, allowing the Sea Cucumber to escape. Other species can eviscerate themselves by shooting their internal organs out of their anus, again, distracting a predator. The Sea Cucumber have the ability to quickly regrow a new digestive tract.

Sea Cucumbers in the Family Holothuriidae are elongate and their skin has fine to large papillae (projections). They vary in color and pattern, but most are black, brown, or greenish. They also vary in size, from small, to over 60 cm (2 feet 0 inches) in length. They are found on, under and within rocks, rubble, and sand from the intertidal zone to depths that exceed 300 m (984 feet). They are active nocturnally. Some species are suspension feeders, filtering food from the surrounding water, and others are depositional feeders, gathering food from the surface of the substrate. Some filter sand through their digestive tracts, removing food from the sand as it passes through. They primarily eat dentris and diatoms. In turn they are preyed upon by crabs, crustaceans, fish, starfish, and sea turtles. Holothuriidae larvae are planktonic, but the adults are benthic. These Sea Cucumbers are either male or female, and fertilization takes place externally. Their larvae is planktonic and the adults are benthic.

The Holothuriidae are found worldwide in temperate and tropical seas. There are currently 185 to 200 known members of the Holothuriidae Family of which 25 are found along the Pacific coast of Mexico.