Ophionereis schayeri

Ophionereis schayeri, known as Schayer's brittle star, belongs to the family Ophionereididae. Its central disk can reach 2.5 centimeters across, and its arms extend up to 15 centimeters. This species feeds by filtering sand and mud from the seafloor to capture detritus and plankton.

Found along the Australian coast, it occurs in New South Wales, Victoria, South Australia, Western Australia, and Tasmania. It is the largest and most common brittle star near Sydney. The species lives from the intertidal zone down to 180 meters deep, often under boulders in tidal areas. When exposed to light, it moves away quickly.

To avoid high temperatures, individuals cluster under boulders in rocky reef habitats. At night, they extend their arms from beneath these boulders to scavenge. Like many tide pool species, O. schayeri may be vulnerable to rising temperatures and ocean acidification caused by climate change.

Like all brittle stars, Schayer's brittle star undergoes metamorphosis through its life cycle, beginning with planktotrophy and shifting to brooded lecithotrophy. The larva is bilaterally symmetrical with a ciliated band. It then becomes a vitellaria larva bordered by ciliary ridges, which soon develops juvenile tube feet and ventral skeletal plates.

This transformation changes the body from bilateral to radial symmetry, resembling other echinoderms. This evolutionary shift from planktotrophic to lecithotrophic development is linked to increased maternal investment, along with larger eggs and higher triglyceride levels. Research on the effects of these triglyceride increases is ongoing.

Similar to the related species O. fasciata, Schayer's brittle star can produce bioluminescence, possibly as a warning to predators. This behavior is thought to require extracellular calcium, acting through the radial nerve cord to trigger light emission. The light-producing cells, called photocytes, are located under the ventral, dorsal, and lateral arm plates. The exact function of this bioluminescence remains unstudied.