Classification of free-living and sedentary polychaetes relies almost exclusively . Most authors accept the annelids as having three major classes: Polychaeta. The most relevant conclusions are: (1) Annelida and Polychaeta are non- monophyletic, even when Classe des annélides polychétes et oligochétes, p. Denkschriften der Kaiserlichen Akademie der Wissenschaften, Mathematisch- naturwissenschaftliche Classe, Wien. 41(2): , plates I-VI., available online.
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In their words, “evolution depends calsse genotypic variation to proceed”. Filo Annelida – Filo Annelida I. This evolutionary line starts with a tagmatization of the anterior body region in the terebelliform polychaetes, which becomes well established in Pogonophora. Biology and ecology of arthworms.
Annelid – Classification |
NaisTubifex sludge worm. Nevertheless, this position was maintained, because any other form of coding the characters for example, as primary absences or secondary losses would also significantly affect the results of the analyses, either by excluding the Ecdysozoa from the polychaetes, or by attracting them to more specialized branches such as the Clitellata. It thus seems plausible to follow this trend through and consider that capillary chaetae and aciculae were further lost at the transition from scale worms to ecdysozoans.
A phylogenetic analysis of the Lumbriculidae Annelida, Oligochaeta.
The true novelty of metameric animals would consist in their reorganizing their body for a new system of locomotion that relies on metameric appendages. Glyceridae and scale worms have four mandibles, while Nereididae and Pilargidae have two.
A few marine annelids that live in tubes lack cuticles, but their tubes have a similar structure, and mucus -secreting glands in the epidermis protect their skins. The opisthosome of Pogonophora is non-informative for deuterostome phylogeny, in the same way that ovoviparity in monotremes is not informative for the phylogeny of mammals.
Evolution in the Annelida. Metameres and coeloms have been considered c,asse in the literature, and yet the homeobox genes responsible for polychata expression of metamerism and of paired appendages, at least, are very largely distributed among the Metazoa.
Rearticulating Annelida with extra assumptions: Evidences of this tagmatization pattern are clearly present in Owenia. Some small tube-dwelling oligochaetes transmit myxosporean parasites that cause whirling disease in fish. Order Cirratulida Sedentary; prostomium pointed and without appendages; 1 or more pairs of tentacular cirri arising from dorsal surface of anterior segments; gills, if present, long and slender, inserted above classd size, minute to 20 cm; examples of genera: Segments bi-annulated, with parapodia inserted on first ring.
Even though some of these features may be absent from the base of Arthropoda, their presence in Onychophora and Tardigrada are quite obvious. Glycera tesselata – Papillae type 1 with transverse ridges It had been expected that a basal parapodium similar to that hypothesized by Fauchald would be found, in which both notopodia Tab. The unordered negative series resulted in parsimonious trees lengthci 0. London, Academic Press, p. Polychaeta, Annelida, and Articulata are not monophyletic: There has been much uncertainty regarding the homology of the cephalic appendages of Polychaeta.
Inversion of dorsoventral axis? The heuristic value of these sequence data is clearly inferior to the genotypic-phenotypic data produced from shared orthologous genes. Setal structure and chaetogenesis in Scolelepis squamata and Malacoceros fuliginosus Spionidae, Annelida. Acta Zoologica, Stockholm For example, two distinct states, an axial and a ventral proboscis, occur in the Spionida. I15, 16 are interpreted here as autapomorphies respectively of Phyllodocidae and Nereididae.
Species with poorly developed or no septa generally have no blood vessels and rely on the circulation within the coelom for delivering nutrients and oxygen. The latter authors argument that the inclusion of groups such as Clitellata Michaelsen, and Pogonophora should be made a priori.
Optimizing some biological features over the phylogeny: Although these groupings do not always represent the most widely accepted taxa in polychaete taxonomy, these groups were chosen in order to reduce to a minimum the potential influence of paraphyletic taxa in the analyses. Evolutionary histories of most characters classe metazoan phyla are still very poorly known. Journal of ZoologyLondon, Apparently no evidence of this pattern has been found in Pogonophora.
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The families of leeches, organized into the four orders outlined above, are generally accepted. The strategy of character analysis should not mold the nature of the data, but phylogenetic hypothesis should be evaluated by the total extrinsic evidence available, and not exclusively by the selected body of intrinsic data the matrix. Coelomate Worms – Eucoelomate fluid filled body cavity. Developmental variation, homology, and the pharyngula stage. There is no information about the presence or absence of nuchal organs in the Pogonophora and other Enterocoela.
The Questidae are here interpreted as a plausible connecting link between the more ancestral marine and estuarine scolecids and the highly derived and predominantly continental Clitellata Fig.
Feeding structures in the mouth region vary widely, and have little correlation with the animals’ diets. Boletin de la Sociedad Entomologica AragonesaZaragoza, Leeches’ eggs are fertilized in the ovaries, and then transferred to the cocoon. Fs, first segment; Gpl, grooved palps; Mp, multiple palps; Pb, parapodial branchiae; Pbn, parapodial chaetal bundles; Pr, peristomial ring; Pro, prostomium; Sp, spionimorph parapodia; Tcr, tentacular crown, Tno, truncate notopodia; To, tori.
Annelid – Wikipedia
The results of this work emphasize three main evolutionary trends within the Metameria. Further sustaining the hypothesis that Clitellata represent a derived group of polychaetes is the indirect evidence presented by Purschkeand Purschke et al. The ultrastructure of the Oligochaeta. CapitellaNotomastusArenicolaMaldaneAxiothella. Glycera lapidum Quatrefages Annelids are considered members of the Lophotrochozoaa “super-phylum” of protostomes clwsse also includes molluscsbrachiopodsflatworms and nemerteans.
The subsequent state of this series polychaega represented by the ventro-lateral palps beginning in the Nephtyidae Fig. Implications for relationships between Vestimentifera and Pogonophora.