Ophionereis schayeri
Largest common brittle star near Sydney, filter-feeder, bioluminescent.
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.
Quick Facts
- Taxon
- Ophionereis schayeri
Facts from the source article.
Lore & Background
Schayer's brittle star is a filter-feeder that sifts sand and mud from the ocean floor for detritus and plankton. It is found off the coast of Australia, including New South Wales, Victoria, South Australia, Western Australia and Tasmania, and occurs from the inter-tidal zone to 180 metres below sea level. This brittle star may be found under boulders in tidal areas and moves quickly away from light when exposed. To reduce exposure to high temperatures, O. schayeri will form clusters under boulders in rocky reef habitats, extending their arms out at night to scavenge for food. Like many species inhabiting tide pools, it may be particularly susceptible to increased temperatures and ocean acidification engendered by climate change.
Reader's Guide
Schayer's brittle star is significant as the largest and most common brittle star found near Sydney, providing a key example of a filter-feeding echinoderm in Australian coastal waters. Its life cycle involves metamorphosis from a bilaterally symmetrical, ciliated larva to a vitellaria larva with ciliary ridges, then to a radially symmetrical adult, reflecting an evolutionary adaptation from planktotrophic to lecithotrophic development associated with increased maternal reliance and larger eggs containing higher triglyceride levels. The species is also notable for its bioluminescence, similar to the related O. fasciata, which may function as a warning to predators; this phenomenon requires extra-cellular calcium and involves photocytes under the ventral, dorsal, and lateral arm plates, though its true functional purpose remains unstudied. Its susceptibility to climate change effects underscores its ecological vulnerability.
Did You Know?
- The central disk is up to 2.5 centimetres wide, with arms to 15 centimetres long.
- Its bioluminescence may function as a warning to predators and requires extra-cellular calcium.
- The larva is bilaterally symmetrical with a ciliated band, later transforming into a radially symmetrical adult.
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