Pterobranchia: Difference between revisions
Adding 18S rRNA phylogeny information. |
Adding alternative genetic code. |
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===Phylogeny=== |
===Phylogeny=== |
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Comparison of [[18S ribosomal RNA]] sequences indicated that pterobranchs are closely related to enteropneust hemichordates.<ref>{{cite journal | author = [[Halanych]] KM. | year = 1995 | title = The Phylogenetic Position of the Pterobranch Hemichordates Based on 18S rDNA Sequence Data | journal = Molecular Phylogenetics and Evolution | volume =4 | issue = 1 | pages = 72–76 | doi =10.1006/mpev.1995.1007 | pmid = 7620637 }}</ref> |
Comparison of [[18S ribosomal RNA]] sequences indicated that pterobranchs are closely related to enteropneust hemichordates.<ref>{{cite journal | author = [[Halanych]] KM. | year = 1995 | title = The Phylogenetic Position of the Pterobranch Hemichordates Based on 18S rDNA Sequence Data | journal = Molecular Phylogenetics and Evolution | volume =4 | issue = 1 | pages = 72–76 | doi =10.1006/mpev.1995.1007 | pmid = 7620637 }}</ref> |
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==Genomics== |
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===Genetic code=== |
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The two pterobranch taxa ''Rhabdopleura compacta'' and ''Cephalodiscus'' use [[Genetic code#Alternative genetic codes|alternative genetic codes]] in their [[mitochondrial genome]].<ref name="Perseke2011">{{Cite journal |last=Perseke |first=Marleen |last2=Hetmank |first2=Joerg |last3=Bernt |first3=Matthias |last4=Stadler |first4=Peter F |last5=Schlegel |first5=Martin |last6=Bernhard |first6=Detlef |date=2011-05-20 |title=The enigmatic mitochondrial genome of Rhabdopleura compacta(Pterobranchia) reveals insights into selection of an efficient tRNA system and supports monophyly of Ambulacraria |url=http://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-11-134 |journal=BMC Evolutionary Biology |language=en |volume=11 |issue=1 |pages=134 |doi=10.1186/1471-2148-11-134 |issn=1471-2148 |pmc=PMC3121625 |pmid=21599892}}</ref><ref name="Li2019">{{Cite journal | last6=Halanych | first6=Kenneth M. | last5=Bernt | first5=Matthias | last4=Cannon | first4=Johanna T. | last3=Tassia | first3=Michael G. | last2=Kocot | first2=Kevin M. | last1=Li | first1=Yuanning | date=2019-01-01 | title=Mitogenomics Reveals a Novel Genetic Code in Hemichordata | journal=Genome Biology and Evolution | language=en | volume=11 | issue=1 | pages=29–40 | doi=10.1093/gbe/evy254 | pmc=6319601 | pmid=30476024}}</ref> |
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==References== |
==References== |
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Revision as of 12:21, 13 April 2020
| Pterobranchia Temporal range:
| |
|---|---|
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| Cephalodiscus dodecalophus | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Hemichordata |
| Class: | Pterobranchia Lankester 1877 |
| Subgroups | |
Pterobranchia is a clade of small worm-shaped animals. They belong to the Hemichordata, and live in secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia attached to tentacles. There are about 30 known living species in the group.
The class Pterobranchia was established by Ray Lankester in 1877. It contained, at that time, the single genus Rhabdopleura. Rhabdopleura was at first regarded as an aberrant polyzoon, but when the Challenger report on Cephalodiscus was published in 1887, it became clear that Cephalodiscus, the second genus now included in the order, had affinities in the direction of the Enteropneusta.
Studies under an electron microscope have suggested that pterobranchs belong to the same clade as the extinct graptolites,[1][2] and phylogenetic analysis suggests that the pterobranchs are living members of the graptolite clade.[3]
Biology
Pterobranchs are small worm-like filter-feeders, living on the ocean floor, often in relatively deep waters. Like their relatives, the acorn worms, their body is divided into three parts: an anterior proboscis, a collar, and a trunk. The proboscis is wide and flattened at the tip, and in most species contains glands that secrete a tube of organic material in which the pterobranch spends its adult life. The animals are mostly colonial, with several zooids living together in a cluster of tubes. In some species, the individual zooids within the colony are connected by stolons. The single member in the genus Atubaria is unusual in lacking the tubes typical of other pterobranchs,[4] but is regarded as a questionable species and is no longer considered valid.[5]
The collar bears a number of large arms, each of which includes a row of tentacles along one side. The number of arms varies between species, with anything from one to nine pairs. The tentacles are covered in cilia and aid in filtering food from the water. The trunk includes a simple tubular gut, and is curved over so that the anus projects upwards, lying dorsal to the collar. Cephalodiscus has a single pair of gill slits in the pharynx, although Rhabdopleura has none.[4]
Development of pterobranchs have been studied only in Rhabdopleura from Plymouth (R. compacta) [6][7] and from Bermuda (R. normani).[8][9] Both of these species are dioecious, with the fertilised egg hatching to produce a free-swimming ciliated larva. Despite the close relationship between the two groups, the larva does not resemble that of the acorn worms; they are "planula-like".[10] Eventually, the larva settles onto the substrate and metamorphoses to an adult. Alternatively, they also reproduce asexually by budding to create a new colony.[4]
Taxonomy
The class is a small one, with only three known families, each containing a single genus.
Class Pterobranchia
- Order Cephalodiscida
- Family Atubaridae
- Genus Atubaria
- Species Atubaria heterolopha Sato, 1935
- Genus Atubaria
- Family Cephalodiscidae
- Genus Cephalodiscus
- Cephalodiscus agglutinans Harmer & Ridewood, 1914
- Cephalodiscus atlanticus Bayer, 1962
- Cephalodiscus australiensis author unknown
- Cephalodiscus calciformis Emig, 1977
- Cephalodiscus densus Andersson 1907
- Cephalodiscus dodecalophus McIntosh 1882
- Cephalodiscus evansi Ridewood
- Cephalodiscus fumosus John, 1932
- Cephalodiscus gilchristi Ridewood, 1908
- Cephalodiscus gracilis Harmer 1905
- Cephalodiscus graptolitoides Dilly 1993
- Cephalodiscus hodgsoni Ridewood, 1907
- Cephalodiscus indicus Schepotieff 1909
- Cephalodiscus kempi John, 1932
- Cephalodiscus levinsoni Harmer
- Cephalodiscus nigrescens Lankester, 1905
- Cephalodiscus sibogae Harmer 1905
- Cephalodiscus solidus Andersson, 1907
- Genus Cephalodiscus
- Family Atubaridae
- Order Rhabdopleurida
- Family Rhabdopleuridae
- Genus Rhabdopleura
- Rhabdopleura annulata Norman, 1921
- Rhabdopleura compacta Hincks, 1880
- Rhabdopleura grimaldi Julien
- Rhabdopleura manubialis Julien 1903
- Rhabdopleura normani Allmann, 1869
- Rhabdopleura striata Schepotieff, 1909
- Genus Rhabdopleura
- Family Rhabdopleuridae
Evolution
Paleontology
The earliest pterobranchs, including Yuknessia and Galeaplumosus, are known from mid-Cambrian Lagerstätten.[11][12] Earlier small carbonaceous fossils are known from the Buen Formation.[13]
Phylogeny
Comparison of 18S ribosomal RNA sequences indicated that pterobranchs are closely related to enteropneust hemichordates.[14]
Genomics
Genetic code
The two pterobranch taxa Rhabdopleura compacta and Cephalodiscus use alternative genetic codes in their mitochondrial genome.[15][16]
References
- ^ Sato, A; Rickards RB; Holland PWH (2008). "The origins of graptolites and other pterobranchs: a journey from 'Polyzoa'". Lethaia. 41 (4): 303–316. doi:10.1111/j.1502-3931.2008.00123.x.
- ^ Fortey, Richard A. (1998). Life: A Natural History of the First Four Billion Years of Life on Earth. New York: Alfred A. Knopf. p. 129. ISBN 978-0-375-40119-0.
- ^ Mitchell, C. E.; Melchin, M. J.; Cameron, C. B.; Maletz, J. R. (2012). "Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite". Lethaia. 46: 34–56. doi:10.1111/j.1502-3931.2012.00319.x.
- ^ a b c Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 1026–1027. ISBN 978-0-03-056747-6.
- ^ Tassia, MG; Cannon, JT; Konikoff, CE; Shenkar, N; Halanych, KM; Swalla, BJ (2016). "The Global Diversity of Hemichordata". PLoS One. 11: e0162564. doi:10.1371/journal.pone.0162564. PMC 5049775. PMID 27701429.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Stebbing, ARD (1970). "Aspects of the reproduction and life cycle of Rhabdopleura compacta (Hemichordata)". Marine Biology. 5 (3): 205–212. doi:10.1007/BF00346908.
- ^ Dilly, PN (1973). "The larva of Rhabdopleura compacta (Hemichordata)". Marine Biology. 18: 69–86. doi:10.1007/BF00347923.
- ^ Lester, SM (1988). "Settlement and metamorphosis of Rhabdopleura normani (Hemichordata: Pterobranchia)". Acta Zoologica. 69 (2): 111–120. doi:10.1111/j.1463-6395.1988.tb00907.x.
- ^ Lester, SM (1986). "Ultrastructure of adult gonads and development and structure of the larva of Rhabdopleura normani". Acta Zoologica. 69 (2): 95–109. doi:10.1111/j.1463-6395.1988.tb00906.x.
- ^ Sato, A; Bishop JDD and Holland PWH (2008). "Developmental biology of pterobranch hemichordates: history and perspectives". Genesis. 46 (11): 587–91. doi:10.1002/dvg.20395. PMID 18798243.
- ^ Loduca, S. T.; Caron, J. B.; Schiffbauer, J. D.; Xiao, S.; Kramer, A. (2015). "A reexamination of Yuknessia from the Cambrian of British Columbia and Utah". Journal of Paleontology. 89: 82–95. doi:10.1017/jpa.2014.7.
- ^ Hou, X. G.; Aldridge, R. J.; Siveter, D. J.; Siveter, D. J.; Williams, M.; Zalasiewicz, J.; Ma, X. Y. (2011). "An Early Cambrian Hemichordate Zooid". Current Biology. 21 (7): 612–6. doi:10.1016/j.cub.2011.03.005. PMID 21439828.
- ^ Slater, Ben J; Willman, Sebastian; Budd, Graham E; Peel, John S (2017). "Widespread preservation of small carbonaceous fossils (SCFs) in the early Cambrian of North Greenland". Geology. 46 (2): 107–110. doi:10.1130/G39788.1.
- ^ Halanych KM. (1995). "The Phylogenetic Position of the Pterobranch Hemichordates Based on 18S rDNA Sequence Data". Molecular Phylogenetics and Evolution. 4 (1): 72–76. doi:10.1006/mpev.1995.1007. PMID 7620637.
- ^ Perseke, Marleen; Hetmank, Joerg; Bernt, Matthias; Stadler, Peter F; Schlegel, Martin; Bernhard, Detlef (2011-05-20). "The enigmatic mitochondrial genome of Rhabdopleura compacta(Pterobranchia) reveals insights into selection of an efficient tRNA system and supports monophyly of Ambulacraria". BMC Evolutionary Biology. 11 (1): 134. doi:10.1186/1471-2148-11-134. ISSN 1471-2148. PMC 3121625. PMID 21599892.
{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link) - ^ Li, Yuanning; Kocot, Kevin M.; Tassia, Michael G.; Cannon, Johanna T.; Bernt, Matthias; Halanych, Kenneth M. (2019-01-01). "Mitogenomics Reveals a Novel Genetic Code in Hemichordata". Genome Biology and Evolution. 11 (1): 29–40. doi:10.1093/gbe/evy254. PMC 6319601. PMID 30476024.
External links
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Pterobranchia". Encyclopædia Britannica (11th ed.). Cambridge University Press.
- Cameron, Christopher B. (2016). A comprehensive list of extant hemichordate species with links to images
- Swalla Billie J. (2007). Class Pterobranchia
