Brittle stars

Brittle stars
	Olive-green brittle star ( Ophiarachna incrassata )
Systematics
without rank:	Tissue animals (Eumetazoa)
without rank:	Bilateria
Over trunk :	Neumünder (Deuterostomia)
Trunk :	Echinoderms (Echinodermata)
Sub-stem :	Eleutherozoa (Eleutherozoa)
Class :	Brittle stars
Scientific name
	Ophiuroidea
	Gray , 1840

The brittle stars (Ophiuroidea) are a class of echinoderms (Echinodermata) and belong there to the sub-tribe of eleutherozoa (Eleutherozoa). The scientific name of this class of animals is derived from gr . ophis - snake and ura - tail off.

features

They are the closest relatives of the starfish and, like them, are characterized by a secondary, five-pointed symmetry. The central disk is very small, the arms are clearly separated from it. There are no suction cups on the feet. Movement is done by moving the arms, which makes them quite nimble. The animals are very sensitive to touch, the arms are often thrown off in danger, but are usually regenerated again. The food of brittle stars consists of detritus , growth , carrion or plankton ( gorgon heads ). The bilaterally symmetrical larvae of brittle stars are known as Pluteus (Ophiopluteus) and live planktonically.

Brittle stars have neither a rectum nor an anus.

Defense against the enemy

Brittle stars are seen as prey by fish looking for food on the sea floor. It is not uncommon for a brittle star to lose an arm. However, this grows back quickly. Some species have glowing gland cells on the thorns of their arms that create a glow when the arm is bitten off. This scares off most of the robbers, so they will be driven to flight.

Systematics and fossil record

Around 150 million year old fossil of a serpent star from the Solnhofen limestone limestone

The brittle stars developed in the early Ordovician about 500 million years ago , but their remains are relatively seldom passed down in fossil form , because the filigree bodies break easily.

Some multi-armed fossils of these animals, as well as certain fossils of sea lilies and starfish (Crinoidea), were called " Medusa head " in a past when these fossilized forms could still arouse horror in their viewers . The sea-dwelling Medusa from Greek mythology turned people to stone by the mere sight of her head covered by snake hair.

Banded brittle star ( Ophiolepis superba )

Gorgon head

Asteriacites

Bright brittle star ( Ophiura albida )

Brittle stars are divided into three orders, six suborders, and 17 families, comprising a total of 250 genera and about 2000 species. This makes them the most species-rich class of echinoderms.

A distinction is made in detail:

Order Oegophiurida
- Subordination to Zeugophiurina
  - Family Ophiocanopidae
Order Ophiurida Müller & Troschel , 1840
- Subordination Chilophiurina Matsumoto, 1915
  - Family Ophiocomidae Ljungman, 1867
  - Family Ophiodermatidae Ljungman, 1867
    - Genus Ophiarachna Müller & Troschel, 1842
      - Ophiarachna incrassata ( olive brittle star )

Order Phrynophiurida Matsumoto, 1915

Suborder Ophiomyxina Fell, 1962
- Family Ophiomyxidae Ljungman, 1866
Subordination to Euryalina Lamarck, 1816
- Family Asteronychidae Müller & Troschel, 1842
- Family Asteroschematidae Verrill, 1899
- Family Euryalidae
- Family Gorgon heads (Gorgonocephalidae) Ljungman, 1867

Individual evidence

↑ Helmut Hölder : Natural history of life . 2nd Edition. Springer-Verlag, Berlin, Heidelberg, New York 1989, pp. 153 .

literature

Svein A. Fosså / Alf Jacob Nilsen: Coral reef aquarium. Vol. 6. Schmettkamp, Bornheim 1998, ISBN 3-928819-18-6 .

Web links

Commons : brittle stars (Ophiuroidea) - Collection of images, videos and audio files

Ophiuroidea Gray, 1840 . In: Integrated Taxonomic Information System.

[1] Helmut Hölder : Natural history of life . 2nd Edition. Springer-Verlag, Berlin, Heidelberg, New York 1989, pp. 153 .