Orthonectida
| Orthonectida | |
|---|---|
 | |
| Two different female Orthonectids | |
Scientific classification  | |
| Kingdom: | Animalia |
| Subkingdom: | Eumetazoa |
| Clade: | ParaHoxozoa |
| Clade: | Bilateria |
| Clade: | Nephrozoa |
| Clade: | Protostomia |
| Clade: | Spiralia |
| Clade: | Platytrochozoa |
| Phylum: | Orthonectida Giard, 1877 [1][2] |
| Species | |
Orthonectida (/ˌɔːrθəˈnɛktɪdə, -θoʊ-/[3]) is a small phylum of poorly known parasites of marine invertebrates[4] that are among the simplest of multi-cellular organisms. Members of this phylum are known as orthonectids.
Biology
[edit]The adults, which are the sexual stage, are microscopic wormlike animals, consisting of a single layer of ciliated outer cells surrounding a mass of sex cells. They swim freely within the bodies of their hosts, which include flatworms, polychaete worms, bivalve molluscs, echinoderms, ribbon worms, acoels, Xenoturbellida, and chordates[5]. Most are gonochoristic, with separate male and female individuals, but a few species are hermaphroditic.[6][7]
When they are ready to reproduce, adults leave the host, and sperm from the males penetrate the bodies of the females to achieve internal fertilisation. The resulting zygote develops into a ciliated larva that escapes from the mother to seek out new hosts. Once it finds a host, the larva loses its cilia and develops into a syncytial plasmodium larva. This, in turn, breaks up into numerous individual cells called agametes (ameiotic generative cells) which grow into the next generation of adults.[6][8]
Classification
[edit]The phylum consists of about 20 known species, of which Rhopalura ophiocomae is the best-known.[4] The phylum is not divided into classes or orders, and contains just two families.
Although originally described in 1877 as a class,[9] and later characterized as an order of the phylum Mesozoa, a 1996 study has suggested that orthonectids are quite different from the rhombozoans, the other group in Mesozoa.[4] The genome of one orthonectid species, Intoshia linei, has been sequenced.[10] These animals are simplified spiralians. The genome data confirm earlier findings which allocated these organisms to Spiralia based on their morphology.[11]
Their position in the spiralian phylogenetic tree has yet to be determined. Some work appears to relate them to the Annelida[12][8] and, within the Annelida, finds them most closely allied to the Clitellata.[13] On the other hand, a 2022 study compensating for long-branch attraction has recovered the traditional grouping of Orthonectida with rhombozoans in a monophyletic Mesozoa placed close to Platyhelminthes or Gnathifera.[14] This supports a previous study which found orthonectids and rhombozoans to make a monophyletic taxon Mesozoa and form a clade with Rouphozoa (platyhelminths and gastrotrichs).[15]
Known species
[edit]Phylum Orthonectida
- Family Rhopaluridae Stunkard, 1937
- Ciliocincta
- Ciliocincta akkeshiensis Tajika, 1979 – Hokkaido, Japan; in flatworms (Turbellaria)
- Ciliocincta julini (Caullery and Mesnil, 1899) – E North Atlantic, in polychaetes
- Ciliocincta sabellariae Kozloff, 1965 – San Juan Islands, WA (USA); in polychaete (Neosabellaria cementarium)
- Intoshia
- Intoshia leptoplanae Giard, 1877 – E North Atlantic, in flatworms (Leptoplana)
- Intoshia linei Giard, 1877 – E North Atlantic, in nemertines (Lineus) = Rhopalura linei
- Intoshia major Shtein, 1953 – Arctic Ocean; in gastropods (Lepeta, Natica, Solariella) = Rhopalura major
- Intoshia metchnikovi (Caullery & Mesnil, 1899) – E North Atlantic, in polychaetes and nemertines
- Intoshia paraphanostomae (Westblad, 1942) – E North Atlantic, in flatworms (Acoela)
- Intoshia variabili (Alexandrov & Sljusarev, 1992) – Arctic Ocean, in flatworms (Macrorhynchus)
- Rhopalura
- Rhopalura elongata Shtein, 1953 – Arctic Ocean, in bivalves (Astarte)
- Rhopalura gigas (Giard, 1877)
- Rhopalura granosa Atkins, 1933 – E North Atlantic, in bivalves (Pododesmus)
- Rhopalura intoshi Metchnikoff – Mediterranean, in nemertines
- Rhopalura litoralis Shtein, 1953 – Arctic Ocean, in gastropods (Lepeta, Natica, Solariella)
- Rhopalura major Shtein, 1953
- Rhopalura murmanica Shtein, 1953 – Arctic Ocean, in gastropods (Rissoa, Columbella)
- Rhopalura ophiocomae Giard, 1877 – E North Atlantic, in ophiuroids (usually Amphipholis)
- Rhopalura pelseneeri Caullery & Mesnil, 1901 – E North Atlantic, polychaetes and nemertines
- Rhopalura philinae Lang, 1954 – E North Atlantic, in gastropods
- Rhopalura pterocirri de Saint-Joseph, 1896 – E North Atlantic, in polychaetes
- Rhopalura vermiculicola
- Stoecharthrum
- Stoecharthrum burresoni Kozloff, 1993
- Stoecharthrum fosterae Kozloff, 1993
- Stoecharthrum giardi Caullery & Mesnil, 1899 – E North Atlantic, in polychaetes
- Stoecharthrum monnati Kozloff, 1993 – E North Atlantic, in molluscs
- Ciliocincta
- Family Pelmatosphaeridae Stunkard, 1937
- Pelmatosphaera
- Pelmatosphaera polycirri Caullery and Mesnil, 1904 – E North Atlantic, in polychaetes and nemertines
- Pelmatosphaera
References
[edit]
- ↑ H. Furuya & J. van der Land (2010). "Orthonectida". World Register of Marine Species. Retrieved January 12, 2011.
- ↑ "Orthonectida Giard, 1877". Integrated Taxonomic Information System. Retrieved January 12, 2011.
- ↑ "Orthonectida". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 2020-03-22.
- 1 2 3 Hanelt, B; Van Schyndel, D; Adema, C. M; Lewis, L. A; Loker, E. S (1996). "The phylogenetic position of Rhopalura ophiocomae (Orthonectida) based on 18S ribosomal DNA sequence analysis". Molecular Biology and Evolution. 13 (9): 1187–91. doi:10.1093/oxfordjournals.molbev.a025683. PMID 8896370.
- ↑ Hiroaki N; Hideyuki M (2019). "A New Species of Orthonectida That Parasitizes Xenoturbella bocki: Implications for Studies on Xenoturbella". The Biological Bulletin. 236 (1). doi:10.1086/700834.
- 1 2 Robert D. Barnes (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 247–248. ISBN 0-03-056747-5.
- ↑ Sliusarev, G. S. (2003). "Orthonectida's life cycle". Parazitologiia. 37 (5): 418–427. PMID 14658313.
- 1 2 Zverkov, Oleg A.; Mikhailov, Kirill V.; Isaev, Sergey V.; Rusin, Leonid Y.; Popova, Olga V.; Logacheva, Maria D.; Penin, Alexey A.; Moroz, Leonid L.; Panchin, Yuri V.; Lyubetsky, Vassily A.; Aleoshin, Vladimir V. (24 May 2019). "Dicyemida and Orthonectida: Two Stories of Body Plan Simplification". Frontiers in Genetics. 10: 443. doi:10.3389/fgene.2019.00443. PMC 6543705. PMID 31178892.
- ↑ Alfred Mathieu Giard (1877). "Sur les Orthonectida, classe nouvelle d'animaux parasites des Échinodermes et des Turbellariés" [On Orthonectida, a new class of parasitic animals of Echinoderms and Turbellarians]. Comptes Rendus (in French). 85 (18): 812–814.
- ↑ Mikhailov, Kirill V; Slyusarev, Georgy S; Nikitin, Mikhail A; Logacheva, Maria D; Penin, Aleksey A; Aleoshin, Vladimir V; Panchin, Yuri V (2016). "The Genome of Intoshia linei Affirms Orthonectids as Highly Simplified Spiralians". Current Biology. 26 (13): 1768–74. doi:10.1016/j.cub.2016.05.007. PMID 27374341.
- ↑ Sliusarev, G. S (2008). "Тип ортонектида (Orthonectida): строение, биология, положение в системе многоклеточных животных" [Phylum Orthonectida: Morphology, biology, and relationships to other multicellular animals]. Zhurnal Obshchei Biologii (in Russian). 69 (6): 403–27. PMID 19140332.
- ↑ Bondarenko, N.; Bondarenko, A.; Starunov, V.; Slyusarev, G. (8 March 2019). "Comparative analysis of the mitochondrial genomes of Orthonectida: insights into the evolution of an invertebrate parasite species". Molecular Genetics and Genomics. 294 (3): 715–727. doi:10.1007/s00438-019-01543-1. PMID 30848356. S2CID 71716789.
- ↑ Slyusarev, George S.; Starunov, Viktor V.; Bondarenko, Anton S.; Zorina, Natalia A.; Bondarenko, Natalya I. (April 2020). "Extreme Genome and Nervous System Streamlining in the Invertebrate Parasite Intoshia variabili". Current Biology. 30 (7): 1292–1298.e3. doi:10.1016/j.cub.2020.01.061. PMID 32084405.
- ↑ Drábková, Marie; Kocot, Kevin M.; Halanych, Kenneth M.; Oakley, Todd H.; Moroz, Leonid L.; Cannon, Johanna T.; Kuris, Armand; Garcia-Vedrenne, Ana Elisa; Pankey, M. Sabrina; Ellis, Emily A.; Varney, Rebecca; Štefka, Jan; Zrzavý, Jan (6 July 2022). "Different phylogenomic methods support monophyly of enigmatic 'Mesozoa' (Dicyemida + Orthonectida, Lophotrochozoa)". Proceedings of the Royal Society B: Biological Sciences. 289 (1978) 20220683. doi:10.1098/rspb.2022.0683. PMC 9257288. PMID 35858055.
- ↑ Lu, Tsai-Ming; Kanda, Miyuki; Satoh, Noriyuki; Furuya, Hidetaka (2017-05-29). "The phylogenetic position of dicyemid mesozoans offers insights into spiralian evolution". Zoological Letters. 3 6. doi:10.1186/s40851-017-0068-5. ISSN 2056-306X. PMC 5447306. PMID 28560048.