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Loxodes rostrum from page 267 of "American journal of physiology" (1898).jpg
Illustration of Loxodes rostrum
Scientific classification
Domain: Eukaryota
(unranked): SAR
(unranked): Alveolata
Phylum: Ciliophora
Subphylum: Postciliodesmatophora
Class: Karyorelictea
Corliss, 1974 [1]
Orders [2]

Karyorelictea is a class of ciliates.

The majority of karyorelict taxa are unculturable, although clonal lines of Loxodes have been developed.


According to Lynn (2008), the Karyorelictea class is divided into three orders:[2]

These three orders were defined morphologically, and have been confirmed with molecular phylogenetics.[3]

Nuclei dimorphism[edit]

All ciliates possess multiple dimorphic nuclei which have separated the functions of protein synthesis, performed by the macronuclei or somatic-nuclei, and heritable DNA replication, performed by the micronuclei or germ-line nuclei. Members of the class Karyorelictea are characterised by an inability to replicate the macronucleus, a process called amitosis, which must be re-synthesized from the micronucleus every cell division.[3]


The term karyorelict derives from the ancient greek κάρυον (káruon), meaning "hard-shelled seed, or nucleus",[4][5] and Latin relictus, meaning 'abandoned', because of the inability of these ciliates to replicate the somatic nucleus.

Alternative genetic code[edit]

An alternative genetic code is used by the nuclear genome of some karyorelictid ciliates (e.g., Parduczia sp.).[6] This code corresponds to translation table 27 and involves the reassignment of three codons:

  • UAA into Gln (Q) ;
  • UAG into Gln (Q) ;
  • UGA into Trp (W) or Termination (*).


  1. ^ WoRMS (2009). "Karyorelictea". World Ciliophora Database. World Register of Marine Species. Retrieved July 21, 2010. 
  2. ^ a b Lynn, Denis (2008-06-24). The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature. Springer Science & Business Media. ISBN 9781402082399. 
  3. ^ a b Ilaria Andreoli; Lara Mangini; Filippo Ferrantini; Giovanni Santangelo; Franco Verni; Giulio Petroni (2009). "Molecular phylogeny of unculturable Karyorelictea (Alveolata, Ciliophora)". Zoologica Scripta. 38 (6): 651–662. doi:10.1111/j.1463-6409.2009.00395.x. 
  4. ^ Bailly, Anatole (1981-01-01). Abrégé du dictionnaire grec français. Paris: Hachette. ISBN 2010035283. OCLC 461974285. 
  5. ^ Bailly, Anatole. "Greek-french dictionary online". www.tabularium.be. Retrieved 2017-01-24. 
  6. ^ Swart, Estienne Carl; Serra, Valentina; Petroni, Giulio; Nowacki, Mariusz (28 July 2016). "Genetic Codes with No Dedicated Stop Codon: Context-Dependent Translation Termination". Cell. 166 (3): 691–702. doi:10.1016/j.cell.2016.06.020. PMC 4967479Freely accessible. PMID 27426948. 

External links[edit]