Ophiopholis aculeata

Ophiopholis aculeata, called the crevice brittle star or daisy brittle star, belongs to the family Ophiactidae. Its range encircles the North Pole, spanning the Arctic Ocean, the northern Atlantic, and the northern Pacific.

Description

The central disc of this brittle star is pentagonal and can reach 2 cm across. It is clearly separated from five sturdy, twisted arms that are about four times longer than the disc is wide. On the underside, the mouth sits within a ring of five toothed jaws. The upper surface of the disc feels granular, and at the base of each arm a pair of large scales—the radial shields—are hidden beneath small spines.

The arms themselves are many-jointed and covered with scales on both sides; the upper side shows a regular row of oval scales, each ringed by smaller ones. Each arm segment carries six or seven stout spines, one of which is short and hooked. Color varies, often reddish or variegated, sometimes purplish, with the central disc scales frequently forming a ten-pointed star and darker bands often appearing on the arms.

Distribution and habitat

This species has a circumboreal distribution. In the North Atlantic, it is common around Iceland, Spitzbergen, and Norway, reaching south to the North Sea. Along eastern North America, it ranges from Greenland down to Long Island.

In the Pacific, it stretches from Japan and the Bering Sea south to California. It typically lives on rocky bottoms, hiding inside shells, hollows, and crevices. Most are found at depths under 300 m, but some have been recorded as deep as 1,880 m.

Biology

Ophiopholis aculeata feeds on detritus and small organisms, capturing them with its tube feet and mucus from glands on its arms. Fish and birds prey on it. The sexes are separate, and fertilization happens externally. Mass spawning events have been observed, where all individuals in one area release their spawn simultaneously, likely triggered by an environmental cue—such as a water temperature change.

In Jamaica, spawning occurs at night between 20:00 and 22:00; in the Gulf of Saint Lawrence, Canada, it happens in both morning and afternoon. In Alaska, spawning tends to occur at 6.5 to 7 °C, while in the White Sea it happens about a degree cooler. Several events have followed downwelling of warmer surface water into deeper, colder layers. The larvae, called ophiopluteus, are planktonic.