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.
HABITAT AND DISTRIBUTION
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
Ophiothrix angulata occurs in dense aggregations in reef rubble throughout the lagoon.
LIFE HISTORY AND POPULATION BIOLOGY
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.
The angular brittle star is a common shallow water species in the Caribbean (Hendler et al. 1999), found in dense aggregations.
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.
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).
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).
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.
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).
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.
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).
No information is available at this time
Boffi E. 1972. Ecological aspects of ophioroids from the phytal of S. W.
Atlantic oncean 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
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
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
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.