Ophionereis reticulata

Ophionereis reticulata, the reticulated brittle star, belongs to the family Ophionereididae. This species lives in shallow waters of the western Atlantic, the Caribbean Sea, and the Gulf of Mexico.

Description

Its body consists of a small, flat, five-sided disc and five long, thin arms. The disc reaches up to 15 mm across, while the arms can extend to 120 mm in length. The upper side of the disc is covered in small plates and is pale grey, marked by a fine network of reddish-brown lines—the pattern that gives the animal its common name.

The arms are made up of many short segments, each fringed with short spines. They are white or pale grey, with a chocolate-brown band appearing roughly every fourth joint. This coloring helps the brittle star blend into its surroundings.

Distribution and habitat

The species ranges from the West Indies and Bermuda through Mexico, Belize, Honduras, Venezuela, and Brazil, with its type location in the Florida Keys. It lives on sandy or gravelly bottoms, among boulders, and under rocks, at depths between 3 and 40 meters.

Behaviour

When moving, Ophionereis reticulata holds its disc above the seafloor and uses its tube feet for locomotion. These feet are long and pointed, and they are the only part of the arm that touches the ground. To move forward, the brittle star bends the base of a tube foot at a right angle, extends the tip forward, then straightens the foot while lifting itself onto the tip. Repeating this action allows it to creep at up to 50 cm per minute, with any arm or pair of arms leading the way.

This brittle star is an herbivore and filter feeder, but its stomach has also been found to contain detritus and bits of polychaete worms. It mainly eats red and green algae and diatoms, catching them by raising one or more arms into the water current while keeping its disc hidden.

If a predator attacks an arm, the arm can break off through autotomy, and the brittle star later regenerates a new one. The sexes are separate, and spawning occurs once a year. The resulting ophiopluteus larvae drift as plankton, passing through several stages before settling on the seabed and metamorphosing into juveniles.