Common names: Angular Brittle Star, more...
Synonyms: Ophiothrix angulata atrolineata HL Clark, 1918, more...
Species Description: Ophiothrix angulata is a member of the class Ophiuroidea that includes the brittle stars and the basket stars. The angular brittle star shares the basic body plan of most members of the Echinodermata with a center disc surrounded by 5 unbranched articulated arms. The spines found along the length of the arms are two times longer than the arm width. The arms have tube feet that are used for locomotion and feeding (Brusca and Brusca 1990). O. angulata is reported to be a highly variable species and it is often difficult to distinguish it from among its congeners. The color of angular brittle star is reported to vary depending upon where it is found (Stancyk and Shaffer 1977). In Florida populations, it often appears orange-red in color with a white line on the anterior of each arm.
Regional Occurrence: The angular brittle star occurs in the western Atlantic from North Carolina to Brazil at depths of 1 - 200 m (Stancyk and Shaffer 1977). Adult Ophiothrix angulata lives in reef rubble (shells), encrusting habitats (sponges), and algae (Boffi 1972, Donachy and Watbe 1986). Juvenile and young adult O. angulata (1.7 - 2.5 mm disc) are reported to occur mainly in the calcareous green alga Halimeda while the adults are found in rubble (Hendler and Littman 1986).
IRL Distribution: Ophiothrix angulata occurs in dense aggregations in reef rubble throughout the lagoon.
Age, Size, Lifespan: In a mature adult the disk diameter measures approximately 10 mm (Hendler et al. 1999). This species is reported to be short lived.
Abundance: The angular brittle star is a common shallow water species in the Caribbean (Hendler et al. 1999), found in dense aggregations.
Regeneration: Ophiothrix angulata is capable of regenerating its missing arms lost by predation or accidental injury (Donachy and Watanabe 1986, Brusca and Brusca 1990). Calcium carbonate ossicles are formed during regeneration.
Reproduction: The reproduction and embryology of Ophiothrix angulata have not been extensively studied compared to other species in this genus. It is reported to undergo sexual reproduction by releasing its gametes into the water column in response to changes in environmental conditions as observed for other members in this genus (Hendler 2006). For spawning to occur, males and females must form dense aggregations (Selvakumaraswamy and Byrne 2000).
Embryology: Ophiothrix angulata have planktotrophic larvae that develop rapidly (Hendler et al. 1999, Hendler 2006). As with other species of Ophiothrix, planktotrophic larvae likely settle and undergo metamorphosis in habitats of adult conspecifics (Morgan and Jangoux 2005). In one study, a juvenile angular brittle star was reported to metamorphose in the water column and recruit on the green alga Halimeda opuntia, which then acts as a secondary dispersal method (Hendler et al. 1999).
Temperature: Ophiothrix angulata occurs at depths from 1 - 200 m, suggesting that it has a relatively high tolerance for temperature change. The timing of a spawning event may be dependent upon fluctuations in seawater temperature.
Salinity: In laboratory experiments, adult Ophiothrix angulata have been shown to be capable of tolerating salinities as low as 20 ‰ for up to approximately 4 days (Stancyk and Shaffer 1977). At lower salinities, the angular brittle star will become immobile after 24 hours; it regains its abilities to move and feed as the salinity increases.
Arm regeneration in adult Ophiothrix angulata has been shown to be reduced in animals kept in sea water at a salinity of 23 ‰. This result was positively correlated with the reduced solubility of calcium carbonate at lower salinities (Donachy and Watanabe 1986).
Trophic Mode: The angular brittle star is a filter-feeder extending its arms into the water column to trap phytoplankton and detritus (Donachy and Watanabe 1986). Food is captured in mucous threads secreted in between the arms (Brusca and Brusca 1990). The tube feet then transport the food to the mouth on the central disc.
Associated Species: Ophiothrix angulata is sometimes found associated with sponges, oysters, or algae (Brusca and Brusca 1990). They are often found in association with other species of Ophiothrix (Hendler 2006).
Boffi E. 1972. Ecological aspects of ophioroids from the phytal of S. W. Atlantic Ocean warm waters. Marine Biology 15:316-328.
Brusca RC and GJ Brusca. 1990. Invertebrates. Sinauer Associates, Inc., Sunderland, MA. pp. 814-832
Donachy JE and N Watanbe. 1986. Effects of salinity and calcium concentration on arm regeneration by Ophiothrix angulata (Echinodermata: Ophiuroidea). Marine Biology 91:253-257.
Hendler GH 2006. Two new brittle star species of the genus Ophiothrix (Echinodermata: Ophiuroidea: Ophiotrichidae) from coral reefs in the southern Caribbean Sea, with notes on their biology. Caribbean Journal of Science 41:583-599.
Hendler GH and BS Littman. 1986. The ploys of sex: relationships among the mode of reproduction, body size and habitats of coral-reef brittlestars. Coral Reefs 5:31-42.
Hendler GH, Baldwin CC, Smith DG, and CE Thacker. 1999. Planktonic dispersal of juvenile brittle stars (Echinodermata: Ophiuroidea) on a Caribbean reef. Bulletin of Marine Science 65:283-288.
Morgan R and M Jangoux. 2005. Larval morphometrics and influence of adults on settlement in the gregarious ophiuroid Ophiothrix angulata fragilis (Echinodermata). Biological Bulletin 208:92-99.
ITIS. Integrated Taxonomic Information System. Available online.
Selvakumaraswamy P and M Byrne. 2000. Reproduction, spawning and the development of 5 ophioroids from Australia and New Zealand. Invertebrate Biology 119:394-402
Smithsonian Tropical Research Institute. Available online.
Stancyk SE and PL Shaffer. 1977. The salinity tolerance of Ophiothrix angulata (Say) (Echinodermata: Ophiuroidea) in latititudinally separate populations. Journal of Experimental Marine Biology and Ecology 29:35-43.
Aboral: In a direction away from the mouth; the part of the body opposite the mouth.
Anal Cone: In crinoids and echinoids, a fleshy projection bearing the anus at its apex; also known as an anal tube.
Apical System: In echinoids, a ring of specialized skeletal plates, including the genital plates and ocular plates; usually located on the highest point of the test.
Arm: In asteroids, crinoids, and ophiuroids, a movable, jointed ambulacral projection, distal to the disk or calyx that carries a radial branch of the water vascular system and the nervous system; sometimes called a ray.
Basket: One of several types of microscopic skeletal ossicles in holothuroids; minute cup-shaped ossicle, usually with four projections.
Button: One of several types of microscopic skeletal ossicles in holothuroids; minute ossicle with four perforations; may be smooth or knobbed.
Disk: The round or pentagonal central body region of ophiuroids and asteroids; see also Terminal Disk.
Distal: In a direction away from the center of the body; for example, toward the tip of the arm in asteroids or the tip of a spine in echinoids.
Dorsal: In echinoderms, this term is variously applied; in asteroids, ophiuroids and echinoids it usually refers to the surface of the body that is opposite the mouth, the surface that is uppermost; in holothuroids, with mouth and anus opposite ends of the cylindrical body, the uppermost surface is considered dorsal; in crinoids, the surface opposite the mouth in considered dorsal by convention, even though it is functionally the ventral (lower) side.
Echinulate: Something spiny or prickly, usually referring to the microscopic texture of a skeletal element such as a spine.
Hermaphrodism: A condition in organisms whereby one individual possesses both functional male and female reproductive structures; hermaphroditic individuals may express both sexes simultaneously, alternately, or sequentially.
Interambulacral Area: An oral or aboral section of the body lying between two ambulacra; in interradius; also known as an interambulacrum.
Interradial: Referring to interambulacral areas of the body; interradius and interradii also commonly used.
Oral: In a direction toward the mouth; a part of the body on the same surface as the mouth.
Oral Papillae: In ophiuroids, small plates at the edge of the mouth, attached to the edges of the jaw plate and/or to the aboral shield; may be variously shaped, from spine-like to scale-like.
Papillae: In holothuroids, specialized dorsal tube feet that lack a suckered tip; in ophiuroids, certain skeletal elements of the jaws or disk.
Papillate: Covered with papillae.
Papillose: Covered with papillae.
Pedicellariae: Small stalked or unstalked pincer-like organs on the body of asteroids and echinoids, used for defense and grooming.
Peltate: Shield-shaped; used to describe the tentacles of some holothuroids.
Perforated Plate: One of several types of microscopic skeletal ossicles in holothuroids; sieve-like and widespread; may also be found in other echinoderm classes, especially in juvenile individuals.
Periproct: In echinoids, a flexible region surrounding the anus, which consists of a membrane containing embedded plates and often bearing spines and pedicellariae.
Plates: One of several types of skeletal elements in echinoderms; tabular structures with a characteristic shape and a fixed position.
Primary Plates: The first-formed plates on the dorsal side of the disk; in ophiuroids, these are the central and five radial plates; in adults, they may form a rosette of scales near the center of the disk, or they may be separated by numerous secondarily developed scales.
Radial: In a direction toward the central axis of an arm or ambulacrum; a part of the body near an arm or ambulacrum.
Radial Shields: Pairs of plates on the dorsal surface of the ophiuroid disk, which lie near the base of each arm; usually relatively large and conspicuous, but may be hidden by granules or superficial scales.
Rods: One of several types of microscopic skeletal ossicles in holothuroids; commonly found as supporting structures in tentacles or tube feet.
Scales: One of several types of skeletal elements in echinoderms; flat, thin structures that are overlapping, tessellate, or haphazardly arrayed.
Sole: In some holothuroids, the flattened ventral part of the body, either covered with or surrounded by tube feet.
Spines: One of several skeletal elements in echinoderms; movable, articulating structures that are long, slender and attenuated.
Teeth: In ophiuroids, small plates or spines attached to the dental plate on the inner edge of the jaw, a series of them extending into the mouth; in echinoids, the five hard, sharp, and movable ossicles incorporated in Aristotle’s lantern; the term also refers to five movable ossicles that surround the anus of some holothuroids.
Tentacle Scales: Small, movable spines or scales, associated with ophiuroid tube feet, which are attached to the ventral arm plate and/or lateral arm plate; may cover the tentacle pores and protect the retracted tube feet.
Tentacles: In holothuroids, feeding structures in the form of highly modified tube feet arranged in a ring around the mouth.
Terminal Disk: Round portion on the end of the tube foot in many echinoderms; usually employed for attachment to substrates.
Tube Feet: Fluid-filled, fingerlike extensions of the water vascular system that protrude through the openings in the skeleton or between skeletal elements; muscles and nerves in the shaft of the tube feet control their movements; glands, and sometimes a muscular sucker, at the tip function in adhesion; specialized tube feet are used for locomotion, feeding, burrowing, respiration, and a combination of functions.
Ventral: In echinoderms, this term is variously applied; in asteroids, echinoids and ophiuroids, it is the surface of the body that carries the mouth; this surface is in contact with the substrate; in holothuroids, with mouth and anus at opposite ends of a cylindrical body, the ventral surface is lowermost, in contact with the substrate; in crinoids, the ventral surface carries the mouth and is functionally the uppermost surface.