Ophiopsila riisei Lütken 1859

“A large specimen measures 12mm (0.5in) in disk diameter and has arms 165mm (6.5in) long. This species like other ophiocomids, has both dental papillae and oral papillae; its specialized inner tentacle scale is typical of the genus Ophiopsila. O. riisei differs from its congeners in having up to seven thick, flattened arm spines. The two most dorsal spines are almost ellipsoidal, short and broad, with a very blunt tip. The more ventral spines are relatively slender; the most ventral spine is longest. Thick integument obscures the disk scales, except for the radial shields and a group of small scales proximal to them.”

Color: “The disk is blotched and the arms are irregularly banded with cream color and shades of gray, reddish, yellowish, maroon, and purplish brown…There are black spots on the dorsal and ventral sides of the disk and arms, and generally there is a small black spot on the lateral arm plate near the base of each spine.” (Hendler, Miller, Pawson, & Kier, 1995, p. 121-122)

“The Bahama Islands, Florida (Palm Beach to the Florida Keys), the Dry Tortugas, Cuba, Haiti, Puerto Rico, St. Thomas, St. Barthelemy, Tortola, Barbados, and the coasts of Central and South America to Brazil.

Depth: Reportedly less than 1-366 m (less than 1-1,200 ft), but about 91 m (300 ft) is a confirmed lower limit.”
(Hendler, Miller, Pawson, & Kier, 1995, p. 121-122).

“From the reef crest to the fore reef slope, in coral and rubble; also found in mangrove peat banks and in clumps of algae.” (Hendler, Miller, Pawson, & Kier, 1995, p. 121).

The size of its egg (0.23 mm in diameter) is consistent with a lecithotrophic pattern of development (Hendler and Littman 1986), but the larva of O. riisei has not been reared or identified. Holmquist (1994) reported that in Florida Bay, Florida, indiviuals are dispersed in clumps of drift algae. The upper lethal temperature for this species is about 40 degrees celsius (Singletary 1971)." (Hendler, Miller, Pawson, & Kier, 1995, p. 121-122).

At night, individuals hold several arms stiffly extended from small crevices and may give corals a hirsute [hairy] appearance; they remain hidden during the day. After dark, they attract attention with a brilliant luminescent display that is triggered when the arms are touched. The luminescence and fluorescence emanate from the arm spine nerve ganglia (Emson and Herring 1985). Grober (1988a,b, 1989) has shown that luminescence, coupled with unpalatability of the species, deters predation by shrimps and crabs. In response to artificial illumination these light-sensitive brittle stars pull their arms into sinusoidal [wave-like] coils before completely withdrawing into the substratum (Hendler, previously unpublished; Hendler and Byrne 1987)." (Hendler, Miller, Pawson, & Kier, 1995, p. 122)

Not common; lives under corals and stones and in crevices

“This species occurs throughout the West Indies and south to Brazil in shallow water among rocks or coral. There are 2 tentacle scales, of which the inner is very long and spatula-shaped. One very good specimen of this form from station 6079, and another, much smaller and broken, from 6080. The latter has the disk gray, with black spots, and the upper-arm plates, instead of being almost square, are twice as long as wide and the outer end rounded.”