Ophiopholis aculeata
A circum-polar brittle star with twisted arms and mass spawning events.
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.
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.
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.
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.
Quick Facts
- Genus
- Ophiopholis
- Species
- aculeata
Facts from the source article.
Lore & Background
Ophiopholis aculeata has a central pentagonal disc up to 2 cm in diameter, clearly set off from five robust, twisted arms. The aboral side of the disc is granular, and a pair of large radial shields at the base of each arm are covered with small spines. The arms are many-jointed and covered with scales; on the aboral surface there is a regular series of oval scales each surrounded by smaller scales. Color varies, often reddish or variegated, sometimes purplish, with central scales on the disc often forming a ten-pointed star and darker bands on the arms.
This brittle star has a circum-boreal distribution. In the northern Atlantic it is common around Iceland, Spitzbergen, and Norway south to the North Sea; on the eastern coast of North America from Greenland south to Long Island; and in the Pacific from Japan and the Bering Sea south to California. It is generally found on rocky substrates, hiding inside shells, hollows, and crevices, at depths less than 300 m but recorded as deep as 1,880 m.
It feeds on detritus and small organisms trapped with its tube feet and mucus secreted by glands on its arms. It is preyed on by fish and birds. The sexes are separate, with external fertilization. Mass spawning events have been observed in Jamaica at night (20:00–22:00 hours) and in both morning and afternoon in the Gulf of Saint Lawrence, Canada. The cue may be a change in water temperature; spawning tends to occur at 6.5–7 °C in Alaska and about a degree cooler in the White Sea. Several spawning events have occurred when warmer surface waters down-welled into deeper, colder layers. The larvae are ophiopluteus larvae that form part of the plankton before settling and metamorphosing into juveniles.
Reader's Guide
Ophiopholis aculeata is significant as a widely distributed brittle star across Arctic and northern temperate oceans, inhabiting rocky substrates and crevices. Its mass spawning behavior, observed in both Jamaica and the Gulf of Saint Lawrence, indicates a coordinated reproductive strategy triggered by environmental cues such as water temperature changes. The species' ability to occur at depths from shallow waters to nearly 1,900 m demonstrates its ecological adaptability. Its feeding method—using tube feet and mucus to trap detritus and small organisms—places it as a key component of benthic food webs, while its role as prey for fish and birds links it to higher trophic levels. The description of its variable coloration, including a ten-pointed star pattern on the disc and banded arms, contributes to its identification in the field. The species' circum-boreal range and presence in both the Atlantic and Pacific Oceans underscore its importance as a model for studying polar and subpolar marine biodiversity.
Did You Know?
- The disc of Ophiopholis aculeata can reach up to 2 cm in diameter, and its arms are four times as long as the disc is wide.
- The larvae of this brittle star are known as ophiopluteus larvae and form part of the plankton.
More in Sea Cucumbers and Brittle Stars, Part 3 1-24
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