Psamminida
| Psamminida | ||||||||||||
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| Scientific name | ||||||||||||
| Psamminida | ||||||||||||
| Tendal , 1972 |
The Psamminida are an order of unicellular, deep-sea living organisms from the group of xenophyophores . With 42 species it represents the larger of the two orders of the xenophyophores.
features
The Psamminida is classified as having a relatively solid body and the absence of so-called linellae, long, thin, protein-containing fibers made of an organic, cement-like material on the casing. The cell nuclei of the Psamminida are usually somewhat smaller than those of the sister order Stannomida . In morphological terms, there are no other common denominators, the species contained are of very diverse shapes.
distribution
Psamminida are distributed almost worldwide in the deep sea, in regions such as the Mediterranean, North and Baltic Seas or the Caribbean they are absent, in Arctic or Antarctic seas, sub-Antarctic and in the South Atlantic they are rare. Although the absolute numbers of finds in these regions also reflect the relatively rare sampling there, they make it clear that tropical to temperate zones between 50 ° N and 50 ° S are the main distribution area.
The locations are at depths of 850 to 6050 meters. However, some finds that cannot be determined with certainty come from significantly shallower depths, such as a possible Occultamina species from the Mediterranean from 760 and a possible Aschemonella from arctic waters from 276 meters depth. In return, photographs of British deep-sea expeditions show occurrences of species of the order down to depths of around 7,800 meters.
Systematics
The Psamminida were first described by Ole Tendal in 1972, and its system is essentially unchanged to the present day, although the scope of the order has since doubled from 21 to 42 species. It comprises twelve genera in four families:
- Psamminida
There are also numerous species that have not yet been validly described, but these can be identified as belonging to the Psamminida, especially in collections in Denmark and Great Britain.