Sedentaria
The division of living beings into systematics is a continuous subject of research. Different systematic classifications exist side by side and one after the other. The taxon treated here has become obsolete due to new research or is not part of the group systematics presented in the German-language Wikipedia.
Sedentaria (the "sitting workers" [neuter] from latin sedere "sit") is the name of a traditional taxon within the annelid class of polychaete (Polychaeta) in which sessile and halbsessile forms, including the tube worms , the as Errantia designated freely moving bristle worms and that goes back to Jean-Baptiste de Lamarck .
features
In contrast to the Errantia, the Sedentaria have no parapodia adapted to rapid or powerful locomotion , so that they lack any aciculae (inner skeletal bristles). Many species build living tubes and have extensive tentacle rings , which allows them a sessile life as filter feeders. Other species, on the other hand, dig tunnels in the sediment and live as substrate eaters .
Sedentaria as an obsolete taxon
Various phylogenetic studies since the 1960s, but especially in the 1990s on an anatomical and molecular genetic basis, have shown that Sedentaria are not a monophyletic group and therefore need to be resolved from a cladistic point of view. As early as 1962, Rodney Phillips Dales rejected the classification into Errantia and Sedentaria in his system, which was based on the internal organs such as the structures of the nephridia . According to the system of Rouse & Fauchald 1998, the former Errantia are grouped together in the new taxon Aciculata - annelid worms whose parapodia have an inner skeleton of aciculae with attached strong muscles and are therefore highly mobile - but Sedentaria are heterogeneous and must be divided into two related groups The Canalipalpata - annelids with at least one pair of palps , on which eyelash grooves run to transport microscopic food particles - to which the typical sedentary tube worms belong with their extensive tentacle crowns , and the Scolecida , which have neither antennae nor palps and usually burrow in the sediment stay, i.e. are predominantly mobile to a limited extent. Both the Aciculata and the Canalipalpata have a pair of palps, which is considered the autapomorphism of a newly established taxon, the palpata . According to this system, the sedentaria do not form a natural group and are obsolete.
Sedentaria in new classifications
However, in more recent phylogenetic analyzes based on molecular genetics, reference is again made to Sedentaria as clade , which not only includes sedentary polychaetes - i.e. the traditional Sedentaria - but also groups that were previously not considered to be polychrome, not even ringworms and numerous free-living ones Include forms. In Andrade and others (2015) and also in Parry and others (2016), both the hedgehog worms (Echiura) and the belt worms (Clitellata) with the little bristles and leeches are included in the Sedentaria, albeit the two family trees of each other differ.
Cladogram according to Andrade et al. 2015:
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Cladogram according to Parry et al. 2016:
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Cladogram according to Struck et al. 2015 and Weigert & Bleidorn 2016:
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literature
- Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Class Polychaeta. P. 67, Classification of the Annelida and Polychaeta: Introduction.
- Jean-Baptiste de Lamarck : Histoire naturelle des Animaux sans Vertèbres, préséntant les caractères généraux et particuliers de ces animaux, leur distribution, leurs classes, leurs familles, leurs genres, et la citation des principales espèces qui s'y rapportent; precedes d'une Introduction offrant la determination des caracteres essentiels de l`Animal, sa distinction du vegetal et desautres corps naturels, enfin, l'Exposition des Principes fondamentaux de la Zoologie. Deterville, Paris 1818.
- Rodney Phillips Dales (1962): The polychaete stomatodeum and the inter-relationship of the families of the Polychaeta. Proceedings of the Zoological Society of London 139, pp. 389-428.
- 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
- Luke A. Parry, Gregory D. Edgecombe, Danny Eibye-Jacobsen, Jakob Vinther (2016): The impact of fossil data on annelid phylogeny inferred from discrete morphological characters. The Royal Society Publishing 2016. DOI: 10.1098 / rspb.2016.1378
- Sónia CS Andrade, Marta Novo, Gisele Yukimi Kawauchi, Katrine Worsaae, Fredrik Pleijel, Gonzalo Giribet, Gregory W. Rouse (2015): Articulating “Archiannelids”: Phylogenomics and Annelid Relationships, with Emphasis on Meiofaunal Taxa. Molecular Biology and Evolution 32 (11), pp. 2860-2875.
- 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
