World Library  
Flag as Inappropriate
Email this Article

Cryptomonad

Article Id: WHEBN0000062299
Reproduction Date:

Title: Cryptomonad  
Author: World Heritage Encyclopedia
Language: English
Subject: Algae, Chroomonas, Falcomonas, Komma caudata, Hemiselmis
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Cryptomonad

Cryptomonads
Rhodomonas salina
Scientific classification
Domain: Eukaryota
Kingdom: Chromalveolata
(unranked): Hacrobia
Phylum: Cryptophyta
Cavalier-Smith, 1986
Class: Cryptophyceae
West in West & Fritsch, 1927
Typical genera

Order Cryptomonadales    Campylomonas
   Chilomonas
   Chroomonas
   Cryptomonas
   Falcomonas
   Geminigera
   Guillardia
   Hemiselmis
   Plagioselmis
   Proteomonas
   Storeatula
   Rhodomonas
   Teleaulax
Order Goniomonadales
   Goniomonas

Synonyms
  • Cryptomonadea Stein, 1878[1]
  • Cryptomonada Senn, 1900
  • Cryptomonadinae Pascher, 1913
  • Cryptomonadophyceae Pascher ex Schoenichem, 1925

The cryptomonads (or cryptophytes)[2] are a group of algae,[3] most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella.

Some may exhibit mixotrophy.[4]

Characteristics

Cryptomonads are distinguished by the presence of characteristic extrusomes called ejectisomes or ejectosomes, which consist of two connected spiral ribbons held under tension.[5] If the cells are irritated either by mechanical, chemical or light stress, they discharge, propelling the cell in a zig-zag course away from the disturbance. Large ejectisomes, visible under the light microscope, are associated with the pocket; smaller ones occur underneath the periplast, the cryptophyte-specific cell surrounding.[6][7]

Cryptomonads have one or two chloroplasts, except for Chilomonas, which has leucoplasts and Goniomonas (formerly Cyathomonas) which lacks plastids entirely. These contain chlorophylls a and c, together with phycobiliproteins and other pigments, and vary in color (brown, red to blueish-green). Each is surrounded by four membranes, and there is a reduced cell nucleus called a nucleomorph between the middle two. This indicates that the plastid was derived from a eukaryotic symbiont, shown by genetic studies to have been a red alga.[8] However, the plastids are very different from red algal plastids: phycobiliproteins are present but only in the thylakoid lumen and are present only as phycoerythrin or phycocyanin. In the case of "Rhodomonas" the crystal structure has been determined to 1.63Å;[9] and it has been shown that the alpha subunit bears no relation to any other known phycobiliprotein.

A few cryptomonads, such as Cryptomonas, can form palmelloid stages, but readily escape the surrounding mucus to become free-living flagellates again. Some Cryptomonas species may also form immotile resting stages with rigid cell walls (cysts) to survive unfavorable conditions. Cryptomonad flagella are inserted parallel to one another, and are covered by bipartite hairs called mastigonemes, formed within the endoplasmic reticulum and transported to the cell surface. Small scales may also be present on the flagella and cell body. The mitochondria have flat cristae, and mitosis is open; sexual reproduction has also been reported.

Classification

Originally the cryptomonads were considered close relatives of the Chromalveolata and to form together with the Haptophyta the group Hacrobia.

One suggested grouping is as follows: (1) Cryptomonas, (2) Chroomonas/Komma and Hemiselmis, (3) Rhodomonas/Rhinomonas/Storeatula, (4) Guillardia/Hanusia, (5) Geminigera/Plagioselmis/Teleaulax, (6) Proteomonas sulcata, (7) Falcomonas daucoides.[10]

Kathablepharids

The kathablepharids, a group of heterotrophic flagellates, have been considered as part of the Cryptophyta since katablepharids were described in 1939.

References

  1. ^ Reviers, B. de. (2006). Biologia e Filogenia das Algas. Editora Artmed, Porto Alegre, p.15.
  2. ^ Barnes, Richard Stephen Kent (2001). The Invertebrates: A Synthesis. Wiley-Blackwell. p. 41. ISBN 978-0-632-04761-1.
  3. ^ Khan H, Archibald JM (May 2008). "Lateral transfer of introns in the cryptophyte plastid genome". Nucleic Acids Res. 36 (9): 3043–53.  
  4. ^ "Cryptophyta - the cryptomonads". Retrieved 2009-06-02. 
  5. ^ Graham, L. E.; Graham, J. M.; Wilcox, L. W. (2009). Algae (2nd ed.). San Francisco, CA: Benjamin Cummings (Pearson).  
  6. ^ Morrall, S.; Greenwood, A. D. (1980). "A comparison of the periodic sub-structures of the trichocysts of the Cryptophyceae and Prasinophyceae". BioSystems 12: 71–83.  
  7. ^ Grim, J. N.; Staehelin, L. A. (1984). "The ejectisomes of the flagellate Chilomonas paramecium - Visualization by freeze-fracture and isolation techniques".  
  8. ^ Douglas, S.; et al. (2002). "The highly reduced genome of an enslaved algal nucleus".  
  9. ^ Wilk, K.; et al. (1999). "Evolution of a light-harvesting protein by addition of new subunits and rearrangement of conserved elements: Crystal structure of a cryptophyte phycoerythrin at 1.63Å resolution.". PNAS 96: 8901–8906. 
  10. ^ "Cryptomonads". Retrieved 2009-06-24. 

External links

  • Tree of Life: Cryptomonads
  • Phylum Cryptophyta at AlgaeBase
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.