''Ophiomastix wendtii'', also known by its common name, the red ophiocoma, and formerly as ''Ophiocoma wendtii'', is a species of

brittle stars Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

that inhabits

coral reefs A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. ...

from

Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

, primarily in the Caribbean sea. These brittle stars have long, thin arms emanating from a small, disk-shaped body, and club-like spines along its arms. They are about the size of an outstretched human hand.

Taxonomy

''Ophiomastix wendtii'' has been referred to by a number of different proposed names. Among these proposed names is ''Ophiocoma riisei'', suggested by Christian Frederik Lütken in 1856, though the name was never commonly accepted. It was originally named ''Ophiocoma wendtii'' by J. Muller and F. H. Troschel in 1842, though in 2018, Timothy O’Hara categorized ''O. wendtii'' under the genus ''Ophiomastix'', as one of four genera previously thought to constitute ''Ophiocoma''. The ''Ophiomastix'' genus is characterized by bearing spines, twice as high as they are wide. ''O. wendtii'' is considered to be among the macrobenthos functional group, alongside its fellow ''Ophiuroidea''. The etymology of ''wendtii'' supposedly comes from a Captain Johann Wilhelm Wendt.

Distribution and habitat

''Ophiomastix wendtii'' is commonly found in reef rubble of the Caribbean Sea, particularly in the Gulf of Mexico. It is most commonly found near Belize and Costa Rica. However, it has been reported as far south as near Brazil. It has also, however, been reported in the Mozambique Channel, between the eastern coast of Africa and Madagascar. It is typically found within a depth range of 1 to 27 meters.

Characteristics and behavior

''Ophiomastix wendtii'', being a member of the ''Ophiomastix'' genus, bears the aforementioned long, club-shaped spines on its arms. ''O. wendtii'' can change its color, by means of phototropic chromatophores. ''O. wendtii'' is typically deep crimson in color, and fades to a neutral beige in the night. Its color can be artificially changed by alterations in light exposure. The ''O. wendtii'' has a system of protection on its arms, covered with calcite crystals. It is thought to reinforce the calcite on its arms with magnesium-rich nanoprecipitates, making its protective crystals more difficult to crack. Much like other echinoderms, ''O. wendtii'' forms a mineralized skeleton. It inhabits reef rubble, and is averse to light, preferring to come out during night over day. The pluteus larvae of ''O. wendtii'' are planktotrophic, feeding on plankton.

Visual system

In addition to functioning as an armor and giving structural support, the crystals on its arms were, until recently, thought to form a visual system. They minimize spherical aberration of incoming light and have excellent optical properties. The lenses were suggested to work by filtering and focusing light on an underlying photoreceptor system. Nerve bundles under each lens, presumed to be light-sensitive, would transmit the optical information to the rest of the nervous system. However, the discovery of nerves and photoreceptor cells in between, rather than beneath, the lenses suggests that this system may not rely on their optical properties. The only known animals to employ a similar visual system were the now-extinct

trilobites Trilobites (; meaning "three-lobed entities") are extinct marine arthropods that form the class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, ...

. Researchers found that ''O. wendtii'' could actively search out areas based on color contrast, suspecting that this might be a behavior designed to evade predators. It is also suspected that its color-changing ability may play a role in its complex vision system.

References

{{Taxonbar, from=Q59450162 Ophiocomidae