is a tropical, shallow subtidal holothurian belonging to the Family Synaptidae
(Sewell et al 1997). The vermiform (worm-like), tentacle-crowned body plan of this species and other synaptids gives the family the misleading common name 'medusa worms.The S. hydriformis
body wall is thin, semi-transparent and elastic. Living specimens are variable in color, ranging from grayish green to reddish brown, with contrasting patches of miliary granules (a type of body wall ossicle) underlying the epidermis. Juveniles tend to be paler and more transparent than adult specimens. Mature adults have a mouth surrounded by 12 pinnate tentacles with a webbed base. Each of these tentacles is covered with as many as 20 pairs of lateral digits and there is a pair of dark pigment spots at the base of each tentacle, on the inner surface near the mouth (Hendler et al. 1995).Synaptula hydriformis
belongs to the Order Apodida
, primarily a burrowing group whose namedenotes the reduction or absence in the group of the locomotory and/or adhesive tube feet (podia) that are the most conspicuous aspect of the water vascular system in most echinoderms. Instead, large numbers (up to 1,500 individuals per square centimeter) of protruding, hooked anchor ossicles in the body wall give the animal the ability to adhere to surfaces in a manner similar to Velcro. Individuals feel sticky and are often found clinging to the neoprene surfaces of wet suits and dive booties after wading or snorkeling through a seagrass bed (Barnes 1987, Hendler et al. 1995, Hendler 2001).The Apodida
, includeing S. hydriformis
, lack the respiratory trees that are the typical gas-exchange organs in sea cucumbers. Instead, cutaneous gas exchange occurs across the body surface (Barnes 1987).