Symbion: Difference between revisions
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[[Category:Platyzoa genera]] |
[[Category:Platyzoa genera]] |
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[[Category:Parasites of crustaceans]] |
[[Category:Parasites of crustaceans]] |
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[[User:Neutral0814|Neutral0814]] ([[User talk:Neutral0814|talk]]) 11:00, 19 November 2018 (UTC) |
Revision as of 13:45, 19 November 2018
Symbion | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Superphylum: | Lophotrochozoa |
Phylum: | Cycliophora |
Class: | Eucycliophora Funch & Kristensen, 1995 |
Order: | Symbiida Funch & Kristensen, 1995 |
Family: | Symbiidae Funch & Kristensen, 1995 |
Genus: | Symbion Funch & Kristensen, 1995 |
Species | |
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Symbion is the name of a genus of aquatic animals, less than 0.5 mm wide, found living attached to the bodies of cold-water lobsters. They have sac-like bodies, and three distinctly different forms in different parts of their two-stage life-cycle. They appear so different from other animals that they were assigned their own, new phylum Cycliophora shortly after they were discovered in 1995.[1] This was the first new phylum of multicelled organism to be discovered since the Loricifera in 1983.
Taxonomy
Symbion was discovered in 1995 by Reinhardt Kristensen and Peter Funch[2] on the mouthparts of the Norway lobster (Nephrops norvegicus), and other, related, species have since been discovered on:
- the American lobster (Homarus americanus, host to Symbion americanus)[3][4]
- the European lobster (Homarus gammarus, host to an as yet unnamed species of Symbion)
The genus is so named because of its commensal relationship with the lobster (a form of symbiosis) – it feeds on the leftovers from the lobster's own meals.[5]
The genus Symbion are peculiar microscopic animals, with no obvious close relatives, and which was therefore given its own phylum, called Cycliophora. The phylogenetic position of Symbion remains unclear: originally the phyla Ectoprocta and Entoprocta were considered possible relatives of Symbion, based on structural similarities.[6] However, genetic studies suggest that Symbion may be more closely related to Gnathifera.
Description
Symbion pandora has a bilateral, sac-like body with no coelom. There are three basic life stages:
- Asexual Feeding Stage – At this stage, S. pandora is neither male nor female. It has a length of 347 μm and a width of 113 μm. On the posterior end of the sac-like body is a stalk with an adhesive disc, which attaches itself to the host. On the anterior end is a ciliated funnel (mouth) and an anus.
- Sexual Stage
- Male – S. pandora has a length of 84 μm and a width of 42 μm during this stage. It has no mouth or anus, which signifies the absence of a digestive system. It also has two reproductive organs.
- Female – S. pandora is the same size as the male in this stage. It does, however, have a digestive system which collapses and reconstitutes itself as a larva.[2]
Reproduction
Symbion can reproduce both asexually by budding and sexually. In sexual reproduction the male attaches to a feeding stage and impregnates a budding female. The female then separates from the feeding stage and attaches herself to another host, where the larva in her develops. The female dies, and the larva escapes. The larval stage may be unscientifically referred to as sea worms. The sexual reproductive cycle is triggered when the host crustacean molts its skin in order to grow.[7]
Effects of shell disease
Reproduction and abundance of Symbion americanus may be adversely affected by the presence of epizootic shell disease (ESD) found on the host crustacean. The Northeast Fisheries Science Center indicates ESD as "circular lesions on the top part of the carapace", which "start out microscopic, but once visible, hundreds of organisms, such as other bacteria, protozoans and nematodes, can be found living in the infected area". If the lobster does not molt in time, the disease ultimately spreads deeper throughout the carapace where the infection penetrates the bloodstream, killing the lobster.[8]
The disease affects not only the carapace but the mouthparts as well, which cause the normally bristle-like mouthpart hairs to become slimy and fragile, easily disintegrating while being handled. Symbion attach to and reproduce on lobster mouthparts, and without sturdy hairs they are unable to adhere. As ESD increases, the amount of habitable American lobsters decreases for Symbion americanus, reducing the abundance on individual lobsters and the community.
While the disease has remained fairly rare in areas like the Gulf of Maine,[9] ESD prevalence can be observed to be as high as 10% to 40% in Southern New England waters depending on sample locations.[10]
References
- ^ Marshall, Michael (28 April 2010). "Zoologger: The most bizarre life story on Earth?". New Scientist. Retrieved 19 November 2018.
... In 1995, Peter Funch and Reinhardt Møbjerg Kristensen, both then at the University of Copenhagen, Denmark, discovered an animal so unlike any other that a new phylum – Cycliophora – had to be created just for it. ...
- ^ a b P. Funch; R. M. Kristensen (1995). "Cycliophora is a new phylum with affinities to Entoprocta and Ectoprocta". Nature. 378 (6558): 711–714. doi:10.1038/378711a0.
{{cite journal}}
: Unknown parameter|lastauthoramp=
ignored (|name-list-style=
suggested) (help) - ^ M. Obst; P. Funch; G. Giribet (2005). "Hidden diversity and host specificity in cycliophorans: a phylogeographic analysis along the North Atlantic and Mediterranean Sea". Molecular Ecology. 14 (14): 4427–4440. doi:10.1111/j.1365-294X.2005.02752.x. PMID 16313603.
{{cite journal}}
: Unknown parameter|lastauthoramp=
ignored (|name-list-style=
suggested) (help) - ^ Neves RC, Kristensen RM, Wanninger A (March 2009). "Three-dimensional reconstruction of the musculature of various life cycle stages of the cycliophoran Symbion americanus". J. Morphol. 270 (3): 257–70. doi:10.1002/jmor.10681. PMID 18937332.
- ^ P. Funch; P. Thor; M. Obst (2008). "Symbiotic relations and feeding biology of Symbion pandora (Cycliophora) and Triticella flava (Bryozoa)". Vie et Milieu. 58: 185–188.
{{cite journal}}
: Unknown parameter|lastauthoramp=
ignored (|name-list-style=
suggested) (help) - ^ "Cycliophorans - Cycliophora - Details - Encyclopedia of Life". Encyclopedia of Life. Retrieved 2017-09-02.
- ^ Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
- ^ Kircun, Christine (9 May 2018). "Lobster Shell Disease". NOAA Fisheries Science Blog. Retrieved 19 November 2018.
... The lesions start out microscopic, but once visible, hundreds of organisms, such as other bacteria, protozoans and nematodes, can be found living in the infected area. ... the lobster has a chance to molt the shell and have a new beginning, disease free with a new shell. Otherwise, the infection enters the blood stream and kills the lobster. ...
- ^ Reardon, Kathleen M.; Wilson, Carl J.; Gillevet, Patrick M.; Sikaroodi, Masoumeh; Shields, Jeffery D. (July 2018). "Increasing prevalence of epizootic shell disease in American lobster from the nearshore Gulf of Maine". Bulletin of Marine Science. 94 (3): 903–921. doi:10.5343/bms.2017.1144. Retrieved 29 September 2018.
- ^ Castro, Kathleen M.; Cobb, J. Stanley; Gomez-Chiarri, Marta; Tlusty, Michael (27 August 2012). "Epizootic shell disease in American lobsters Homarus americanus in southern New England: Past, present and future" (PDF). Diseases of Aquatic Organisms. 100 (2): 149–158. doi:10.3354/dao02507. Retrieved 29 September 2018.