| 词条 | Loxodes |
| 释义 |
| image = Loxodes rostrum from page 267 of "American journal of physiology" (1898).jpg | image_upright = 0.5 | image_caption = Illustration of Loxodes rostrum | display_parents = 4 | taxon = Loxodes | authority = Ehrenberg, 1830 | subdivision_ranks = Species | subdivision = Several, including:[1]
}} Loxodes is a genus of karyorelictean ciliates, belonging to family Loxodidae.[1] It is the only known karyorelictean ciliate that lives in freshwater habitats. The term Loxodes derives from the ancient greek {{wikt-lang|grc|λοξός}} ({{grc-transl|λοξός}}), meaning "oblique, tilted".[2][3] EcologyLoxodes lives in freshwater habitats such as lakes and ponds, unlike other karyorelictean ciliates such as the other loxodid genus Remanella, which live in brackish-water or marine habitats.[4] They feed on bacteria and protists such as microalgae.[5] It is microaerobic, preferring low concentrations of oxygen, below 5% atmospheric saturation. It can also survive extended periods in anoxic water, where oxygen is absent. Under such conditions, Loxodes is able to use nitrate instead of oxygen as an electron acceptor for respiration.[6] Nitrate respiration is rare among eukaryotes, and Loxodes was the first eukaryote known to have this capability. Loxodes is also sensitive to light. GeotaxisBoth genera in the family Loxodidae have organelles known as Müller (or Müllerian) vesicles, which are involved in the sensing of gravity. They are about 7 µm across, and contain a membrane-covered mineral body known as a statolith. In Loxodes, the statolith is mostly composed of barium salts, compared to Remanella, where they are mostly strontium. Its structure and function resembles the statocyst of some animals.[4] Loxodes uses its Müller's vesicle to distinguish between up and down (geotaxis or gravitaxis), which it uses as a stimulus in addition to the oxygen concentration to orient itself in the water column. When oxygen concentrations are high, Loxodes tends to swim downwards, and vice versa.[7] Genetic codeLoxodes uses a variant of the standard genetic code, where the stop codons UAA and UAG have been reassigned to the amino acid glutamine. This variant code is also used by other ciliates.[8]Cell cycleUnlike other ciliates, the macronuclei of kayorelicteans do not divide. This was first observed in Loxodes by Otto Bütschli in the 1870s.[9] It was later shown to be a distinctive feature of the class Karyorelictea in general. Experiments on Loxodes have shown that little or no DNA synthesis occurs in their macronuclei, and that the DNA content of a macronucleus is only slightly more than that of a diploid micronucleus ("paradiploid").[9] References1. ^1 {{Cite web|url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=415581|title=WoRMS - World Register of Marine Species - Loxodes Ehrenberg, 1830|website=www.marinespecies.org|access-date=2017-02-15}} 2. ^{{Cite book|title=Abrégé du dictionnaire grec français|last=Bailly|first=Anatole|date=1981-01-01|publisher=Hachette|isbn=978-2010035289|location=Paris|oclc=461974285}} 3. ^{{Cite web|url=http://www.tabularium.be/bailly/|title=Greek-french dictionary online|last=Bailly|first=Anatole|date=|website=www.tabularium.be|publisher=|access-date=2017-01-24}} 4. ^1 {{Cite journal|last=Fenchel|first=Tom|last2=Finlay|first2=Bland J.|date=1986-02-01|title=The Structure and Function of Müller Vesicles in Loxodid Ciliates|journal=The Journal of Protozoology|language=en|volume=33|issue=1|pages=69–76|doi=10.1111/j.1550-7408.1986.tb05560.x|issn=1550-7408}} 5. ^{{Cite book|title=The ciliated protozoa : characterization, classification, and guide to the literature|last=H.|first=Lynn, Denis|date=2008|publisher=Springer|isbn=9781402082382|location=New York|pages=343|oclc=272311632}} 6. ^{{Cite book|title=Ecology and evolution in anoxic worlds|last=Fenchel|first=Tom|last2=Finlay|first2=Bland J.|date=1995|publisher=Oxford University Press|isbn=978-0198548386|location=Oxford|pages=129|oclc=31046101}} 7. ^{{Cite journal|last=Fenchel|first=T.|last2=Finlay|first2=B. J.|date=1984-05-01|title=Geotaxis in the Ciliated Protozoon Loxodes|url=http://jeb.biologists.org/node/1054932.full|journal=Journal of Experimental Biology|language=en|volume=110|issue=1|pages=|issn=0022-0949|via=}} 8. ^{{Cite journal|last=Bezerra|first=Ana R.|last2=Guimarães|first2=Ana R.|last3=Santos|first3=Manuel A. S.|date=2015-11-12|title=Non-Standard Genetic Codes Define New Concepts for Protein Engineering|url=http://www.mdpi.com/2075-1729/5/4/1610|journal=Life|language=en|volume=5|issue=4|pages=1610–1628|doi=10.3390/life5041610|pmid=26569314|pmc=4695839}} 9. ^1 {{Cite journal|last=Raikov|first=Igor B.|date=1985|title=Primitive never-dividing nuclei of some lower ciliates|url=|journal=International Review of Cytology|volume=95|pages=267–325|via=|pmid=2414246}} External links
2 : Karyorelictea|Ciliate genera |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。