Orbiniida
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| Scientific name | ||||||||||||
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| Fauchald , 1977 |
Orbiniida is the name of an order of many bristles that, depending on the description, only includes the Orbiniidae family with some large species burrowing in the soft subsoil, or an order including the Orbiniidae, Paraonidae and Questidae , or alongside the Orbiniidae (excluding the latter two families) also includes other families with very small species that live in the sand gap system and feed on bacteria in seas worldwide.
features
The Orbiniida in the narrower sense have an elongated, worm-shaped body with a conical or rounded prostomium , on which there are no antennae, but a pair of slit-shaped nuchal organs and sometimes a pair of small, deeply sunken eyes. Palps are also absent; An exception are the Nerillidae , counted according to Struck and others , in which a pair of palps sits on the prostomium. The Orbiniidae have a bristle-free buccal ring of one or two segments without attachments. The ventrally located, jawless and toothless pharynx , which can be turned out in the larger forms, is soft, sack-like, slightly lobed or branched, in small forms of the sandgap fauna it is very muscular and cannot be everted. The animals have numerous segments with two- branched parapodia on which only simple bristles sit - capillary-shaped bristles and mostly also spines and sawn or prickly bristles.
Systematics
Kristian Fauchald established the Annelid order Orbiniida with the families Orbiniidae , Paraonidae and Questidae in 1977 , as the characteristics of which he named in particular missing antennae and palps, an evertable pharynx and two-branched parapodia with simple bristles. In 1982, however, Marian Hope Pettibone restricted the order Orbiniida to the family Orbiniidae. Kristian Fauchald and Gregory Rouse 1997 no longer named the taxon Orbiniida, but included the families Orbiniidae, Paraonidae and Questidae, which were previously summarized here, on the basis of the missing palps and antennae as well as more than a pair of cirrus pygidium to the Scolecida .
Struck, Golombek and other prepared taxon Orbiniida new scope to the families of 2,015 phylogenetic due to investigations on a molecular genetic basis Orbiniidae , Parergodrilidae , Diurodrilidae , Dinophilidae and Nerillidae on, which in turn hereafter a sister group to a clade is composed of the Clitellata , Terebellida , Arenicolidae , Opheliidae , Capitellidae , Echiura , Spionida , Sabellida , Cirratulidae and Siboglinidae , and with this forms a group called Sedentaria , which is much more extensive than the earlier taxon Sedentaria. From this work, it appears that the in sand gap systems living (Interstitia) Orbiniida - Parergodrilidae, Diurodrilidae, Dinophilidae and Nerillidae - by Progenese reached adaptation to this habitat, while an unspecified related other Annelidengruppe the sand gap systems, leading to a greatly expanded taxon Errantia belonging Protodriliformia , developed into the tiny forms known today through dwarfing in ever finer sediments. In the past, some authors summarized all sand-gap-dwelling annelids - i.e. Protodriliformia and Orbiniida - to form the so-called Archiannelida (also Archiannelides, "old ringelworms"), whose similarities are now viewed as convergence .
The cladogram of the Sedentaria with the Orbiniida resulting from this work looks like this:
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literature
- Kristian Fauchald (1977): The polychaete worms, definitions and keys to the orders, families and genera. Natural History Museum of Los Angeles County: Los Angeles, CA (USA), Science Series. 28, pp. 1 - 188, here Order Orbiniida , p. 14.
- Marian Hope Pettibone: Annelida. In: Sybil P. Parker (Ed.): Synopsis and Classification of Living Organisms , Vol. 2, pp. 1-43. McGraw-Hill, New York 1982. pp. 21f., Orbiniida, Orbiniidae.
- Gregory W. Rouse, Kristian Fauchald (1998): Recent views on the status, delineation, and classification of the Annelida. (PDF). American Zoologist. 38 (6), pp. 953-964. doi: 10.1093 / icb / 38.6.953
- Torsten Hugo Struck, Anja Golombek, Anne Weigert, Franziska Anni Franke, Wilfried Westheide, Günter Purschke, Christoph Bleidorn, Kenneth Michael Halanych (2015): The Evolution of Annelids Reveals Two Adaptive Routes to the Interstitial Realm Current Biology. Current Biology 25 (15), pp. 1993-1999. DOI: 10.1016 / j.cub.2015.06.007
- Anne Weigert, Christoph Bleidorn (2016), Current status of annelid phylogeny. Organisms Diversity and Evolution 16 (2), pp. 345-362. DOI: 10.1007 / s13127-016-0265-7
Web links
- Orbiniida . In: Lexicon of Biology , online edition.