Glass sponges
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Glass sponge on a coral of the genus Lophelia |
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| Hexactinellida | ||||||||||||
| EO Schmidt , 1870 |
The glass sponges (Hexactinellida ( Gr .: Sechsstrahlige)) are a class from the trunk of the sponges (Porifera). The glass sponges include around 600 species that live exclusively in the sea, from the littoral to the deep sea (as of 2013). Glass sponges represent 8% of all known types of sponge. They are currently divided into 19 families and 125 genera.
Overview
In their skeleton, glass sponges have six-pointed needle shapes or needle shapes that can be derived therefrom, which are made up of amorphous water-containing silicon dioxide (biogenic opal ). The name of the class due to the morphology of its skeletal elements goes back to the zoologist Eduard Oscar Schmidt . Up to 20 differently shaped needle types can occur in one type of glass sponge. The glass sponges are attached to the substrate either with the base or with a bundle of long glass threads. An exception is the species Monorhaphis chuni , which produces a gigantic single sponge needle up to 3 m long and 8 mm thick, with which the sponge is anchored in the deep sea floor of the Indian and Pacific Oceans.
Hexactinellida occur in all oceans, they are (with a few exceptions) deep-sea inhabitants. They reach a particularly high density in the waters around the Antarctic continent at a depth of 100 to 500 m. Although they are only found there in a few species, they can make up up to 90% of the living things ( benthos ) sitting on the sea floor . The large glass sponges with their numerous cavities offer other invertebrate species, but also young fish, a place to live and shelter. After the sponges die, their skeletal needles remain on the ground and, over time, form up to 2 meters thick, glass wool-like needle mats that structure and change the seabed. Glass sponges are therefore an important ecological factor in the Antarctic .
The highest number of species in a limited region was filled with about 70 different species on the east coast of Japan in front of Tokyo located Sagami Bay counted. The occurrence of glass sponges from this region, at depths of 150 to 1000 m, has been known to science since the 1830s. The species Hyalonema Sieboldii , at that time still called "glass plant" or "glass coral", was used in ancient Japan to make room decorations or hairpins.
Glass sponges are among the oldest multicellular animals in the history of the earth. They have been detected in rock layers that are around 545 million years old ( Ediacara Formation , Upper Precambrian). They reached their highest distribution in the Upper Jurassic , about 200 million years ago, in the shallow waters of the Tethys . At that time, a 7000 km long sponge reef belt stretched from today's Caucasus , across Romania , southern Germany , the Iberian Peninsula to today's coast of Newfoundland . This made the Hexactinellida important reef builders, comparable to the corals living today . The limestone cliffs in the Franconian Alb are z. B. fossil remains of such glass sponge reefs. The only larger glass sponge reef known today covers around 1000 square kilometers off the west coast of Canada.
A specimen of Monoraphis chuni was found in the East China Sea , which formed needles 3 meters long and 1 centimeter thick during its 11,000-year lifespan, the " annual rings " of which serve as a climate archive and document strongly fluctuating water temperatures (between 2 and 10 degrees Celsius).
The main features of the mechanism of needle formation in the Hexactinellida have been clarified. The needles consist of concentrically separated layers around a central hollow channel, which is filled by an organic axial filament. This consists largely of the silicate-secreting enzyme silicatein, which belongs to the cathepsin subfamily. Another enzyme, the silicase, is used to keep the amorphous silicon in solution. Silicase is related to the carbon anhydrases, the active center is a metal complex with the participation of zinc. In addition to the amorphous silicate glass mass, the finished needles consist to a large extent of structural proteins , probably to a large extent collagen . The " composite material " made of silicate glass and protein is more elastic than pure glass: It is possible to bend a sponge needle into a circular shape; when you let go, it returns to its original shape undamaged.
Systematics
The glass sponges with about 500 known species are divided into two subclasses :
gallery
Glass sponges based on drawings by Franz Eilhard Schulze (1840–1921)
Microsclera (star-shaped; dark) in the tissue of a glass sponge
The Japanese Hexactinellida researcher Isao Ijima (1861–1921) at his workplace surrounded by dry specimens of large glass sponges from Sagami Bay
The chaunangium crater glass sponge , captured on the Valdivia expedition in the years 1898–1899
An unspecified species of Hexactinellida
Unknown Hexactinellida species on cowrie shells
literature
- John N. Hooper, Rob W. van Soest (eds.): Systema Porifera: A Guide to the Classification of Sponges. Kluver Academic / Plenum Publishers, New York 2002, ISBN 978-0-306-47260-2 .
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- ↑ Rob WM Van Soest, Nicole Boury-Esnault, Jean Vacelet, Martin Dohrmann, Dirk Erpenbeck, Nicole J. De Voogd, Nadiezhda Santodomingo, Bart Vanhoorne, Michelle Kelly, John NA Hooper, John Murray Roberts: Global Diversity of Sponges (Porifera) . In: PLoS ONE . 7, 2012, p. E35105, doi: 10.1371 / journal.pone.0035105 .
- ↑ World Porifera Database 2013
- ↑ Bernadette Calonego: dinosaurs of the seas . In: Süddeutsche Zeitung . May 11, 2010 ( sueddeutsche.de [accessed December 31, 2016]).
- ↑ Spectrum of Science , June 2012, p. 11; based on: Klaus Peter Jochum, Xiaohong Wang, Torsten W. Vennemann, Bärbel Sinha, Werner EG Müller : Siliceous deep-sea sponge Monorhaphis chuni: A potential paleoclimate archive in ancient animals . In: Chemical Geology . tape 300/301 , March 2012, p. 143–151 , doi : 10.1016 / j.chemgeo.2012.01.009 (English).
Web links
- Glass sponges - dinosaurs of the seas . Süddeutsche Zeitung , May 11, 2010