Sand dollars
| Sand dollars | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Clypeasteroida | ||||||||||||
| A. Agassiz , 1872 |
The sand dollars (Clypeasteroida) belong to the class of sea urchins . They live on the shallow sandy shores of all seas, where they feed on fine organic particles that stick to the surface of the grains of sand. In addition, some species can be carried along by the movement of the tides and temporarily bury themselves in the sand, where they can easily survive the ebb tide . Other species only live in the coastal waters on the sandy bottom.
In contrast to the real sea urchins , the sand dollars have very small spines. Their flat skeletons, composed of lime flakes, are covered by a thin epidermis and innumerable cilia . These fine hairs are always in flickering motion and, among other things, lead the food components over the body to the mouth area. Unlike the regular sea urchins and the other echinoderms , which have pentaradial body symmetries, the flat bodies of the sand dollars are bilaterally symmetrical , with the mouth and anus on the underside. Nevertheless, its radial five-part division can still be seen.
A large number of ambulacral feet allow the sand dollars to move slowly, but only forwards, possibly with slight deviations to the sides. The sand dollars can also bury themselves completely in the sand within a minute.
On the top of the body, ambulacral feet responsible for breathing are arranged like five-fold petals. Many types of sand dollars have regularly arranged cuts or holes in the flat disc.
Like all sea urchins, the sand dollars have a jaw apparatus known as Aristotle's lantern . The construction of this lantern of Aristotle is simplified for the sand dollars. A five-pointed star composed of five elements carries the constantly growing teeth in the center.
Systematics
- Suborder Clypeasterina L. Agassiz, 1872
- Family Arachnoididae Duncan, 1889
- Family Clypeasteridae L. Agassiz, 1835
- Subordination Scutellina Haeckel, 1896
- Infraorder Scutelliformes Haeckel, 1896
- Astriclypeidae Stefanini family , 1912
- Family Dendrasteridae Lambert, 1889
- Family Echinarachniidae Lambert, 1914
- Family Mellitidae Stefanini, 1911
- Family Scutellidae Gray, 1825
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Infraorder Laganiformes Desor, 1857
- Family Echinocyamidae Lambert & Thiery, 1914
- Family Fibulariidae Gray, 1855
- Family Laganidae Desor, 1859
- Family Rotulidae Gray, 1855
- Infraorder Scutelliformes Haeckel, 1896
various
The sand dollar is the symbol of the International Society for Ecological Economics . In addition, a Rotula deciesdigitatus sand dollar is the symbol of the World Register of Marine Species .
literature
- Volker Storch, Ulrich Welsch: Systematic Zoology . G. Fischer, Stuttgart 1997, ISBN 3-437-25160-0
- Horst Füller u. a .: Urania animal kingdom, invertebrates: 2 . 2nd Edition. Urania-Verlag, Leipzig 2000, ISBN 3-332-01175-8
Web links
- Integrated Taxonomic Information System Clypeasteroida A. Agassiz, 1872
Individual evidence
- ^ Website of the International Society for Ecological Economics, accessed on November 1, 2014.
- ^ WoRMS - World Register of Marine Species. Retrieved January 4, 2019 .