Olive green brittle star
| Olive green brittle star | ||||||||||||
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Olive-green brittle star ( Ophiarachna incrassata ) |
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| Ophiarachna incrassata | ||||||||||||
| ( Lamarck , 1816) |
The olive-green brittle star ( Ophiarachna incrassata ) lives on sandy soils and coral debris in the coral reefs of the tropical Indo-Pacific . It occurs from the coast of East Africa to Japan , Hawaii and the islands of the South Pacific at depths of 5 to 40 meters. It is relatively rare in the western Indian Ocean, common from Sri Lanka to Hawaii. It is able to catch small fish , but it also eats other small animals and carrion .
features
The olive-green brittle star is relatively large. Its body reaches a diameter of five centimeters, the five arms reach four to five times the body diameter and are up to 25 centimeters long. Its color is olive green, specimens from deep regions can also be bright yellow-green or lemon-yellow. On the top of the body there is a pattern of small, rows of light points that can be framed in a dark color. The arms are one color. Only the spines on the arm sides, which are longer than the arm segments, are light and green or brown ringed.
Lifestyle and diet
The olive-green brittle star is nocturnal and hides under stones during the day. It feeds mainly on bottom-dwelling invertebrates, but also eats carrion and detritus . In Australian waters, it has been observed to target small diurnal fish that return to their night quarters at dusk. The brittle star simulates a small natural cavity into which some fish swim. As soon as a fish is under the brittle star's body disc, it quickly closes its arms around the prey. In Raine Island National Park , he ate the remains of sea turtles that tiger sharks had left with their meals.
Reproductive cycle
How it reproduces is unknown. It is believed, however, that the olive-green brittle star is a brood-tending species that tends its larvae in brood pouches on the underside of the body. Marine aquarists have reported the sudden appearance of tiny red brittle stars measuring less than a millimeter in diameter on the live rock . The young are diurnal and may initially feed on sponges . With a diameter of 16 millimeters, the outer third of the arms initially turned green. The transition zone to the red arm part close to the body is a narrow yellow band. When the diameter is four to five centimeters, the color change is complete and the brittle stars have the appearance of the adult animals.
Aquarium keeping
The olive-green brittle star is caught for the purpose of aquarium keeping and is long-lived and persistent in saltwater aquariums. It is voracious and, if not adequately fed, can overwhelm small fish.
literature
- Harry Erhardt, Horst Moosleitner: Mergus Sea Water Atlas Volume 3 , Mergus-Verlag, Melle, ISBN 3-88244-103-8
- Svein A. Fossa, Alf Jacob Nilsen: Korallenriffaquarium Volume 6 , Schmettkamp Verlag, 1998, ISBN 3-928819-18-6
- Maria Byrne: Ophiarachna incrassata, the fishing ophiuroid. In: Maria Byrne, Timothy O'Hara: Australian Echinoderms: Biology, Ecology and Evolution. Csiro Publishing, Melbourne 2017. p. 17. With drawing depicting the catch of fish by the brittle star ( Google Books ).
- JG Morin: Piscivorous behavior and activity patterns in the tropical ophiuroid Ophiarachna incrassata (Ophiuroidea: Ophiodermatidae). In: RD Burke, PV Mladenov, P. Lambert, RL Parsley (Eds.): Echinoderm Biology. Balkema, Rotterdam 1988. pp. 401-407.
Web links
- Integrated Taxonomic Information System Ophiarachna incrassata