Daisy brittle star

Language English

Onglets

Description

Distinguishing features

The daisy brittle star has a central body disk measuring about 2 cm in diameter, with 5 arms that are 9 cm long. Unlike sea stars, the daisy brittle star has long thin arms that do not contain any digestive or reproductive organs. The arms have several small articulated segments, making them flexible and able to move in all directions.

The daisy brittle star is generally reddish in colour, covered in small spots or lines.

The underside of the daisy brittle star’s central body disk has a mouth with 5 small white teeth. Small tentacles can be seen under the arms; these are tube feet, or podia. Unlike the tube feet of sea stars and sea urchins, the daisy brittle star’s feet do not play a role in its locomotion.

Reproduction

There are both male and female daisy brittle stars. They reach sexual maturity at the age of two, but continue to grow until the age of three or four.

They reproduce in late summer. Males and females release their sperm and eggs into the water, where fertilization takes place. The larvae swim freely among plankton for several weeks. Then the young (which resemble miniature adults at this point) settle on the seafloor.

As with sea stars, if part of an arm breaks off it can regenerate a whole new body as long as the section includes part of the central disk.

Diet

Daisy brittle stars are detritivore organisms. They use their long articulated arms to locate and pick up their food on thye sea floor.

Daisy brittle stars sometimes attack small sea worms called polychaeta, or even small crustaceans.

Predators

To survive attacks by predators or humans, a daisy brittle star can discard the end of an arm. The articulated arms have weak spots around the articulations. When a predator grabs a daisy brittle star, there is a struggle and the brusque movements cause an articulation to break off. The predator is left holding the end of the arm that has been wrenched off, while the daisy brittle star makes a getaway and hides under a rock.

Daisy brittle stars may fall victim to fish, ducks (harlequin ducks), sea urchins or sea stars. Crabs are their most fearsome predators.

Habitat

Daisy brittle stars are found off the North Atlantic coast, from the Arctic to Cape Cod, as well as in Ireland and the United Kingdom. They also frequent the waters of the Estuary and Gulf of St. Lawrence, and are present in the North Pacific.

Daisy brittle stars can be seen on or under rocks, on the seafloor, in rock crevices, or buried in sludge or sand, from low tide down to depths of 1,500 m.

Ecology, behaviour

Daisy brittle stars are generally shy and frequently hide under rocks. They are the most active echinoderms, moving around quickly and easily. Their long arms unfurl, grasp and then pull the central body disk forward. Daisy brittle stars are primarily active at night (nocturnal), shunning the light of day.

Hiding in rock crevices, daisy brittle stars take cover from many predators, such as sea urchins. However, that strategy does not spare them from attacks by common sea stars (Asterias rubens).

In the 18^th century, Indonesians reportedly ate daisy brittle stars. Unlike sea stars, which are harvested, dried and used in home decor, daisy brittle stars are fragile and are seldom used as decorative accessories.

French name

Ophiure pâquerette

Scientific name

Ophiopholis aculeata

Phylum

Echinodermata

Class

Ophiuroidea

Order

Ophiurida

Family

Ophiactidés

Size

Diameter of central body disk: 2 cm Arms: 9 cm long Overall diameter: 20 cm

Life span

5 years

Status

Not endangered, but sensitive to pollution and habitat degradation.

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