| Bikonts Temporal range:Mesoproterozoic –present | |
|---|---|
 | |
| Aradiolarian | |
Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | Orthokaryotes |
| (unranked): | Neokaryotes |
| (unranked): | Bikonta Cavalier-Smith, 1993 |
| Subgroups | |
| Synonyms | |
| |
Abikont ("two flagella") is any of theeukaryotic organisms classified in the groupBikonta. Many single-celled and multi-celled organisms are members of the group, and these, as well as the presumed ancestor, have twoflagella.[1]
Another shared trait of bikonts is the fusion of twogenes into a single unit: the genes forthymidylate synthase (TS) anddihydrofolate reductase (DHFR) encode a singleprotein with two functions.[2]
The genes are separately translated inunikonts.
Some research suggests that a unikont (a eukaryotic cell with a single flagellum) was the ancestor ofopisthokonts (Animals, Fungi, and related forms) andAmoebozoa, and a bikont was the ancestor ofArchaeplastida (Plants and relatives),Excavata,Rhizaria, andChromalveolata.Cavalier-Smith has suggested thatApusozoa, which are typically consideredincertae sedis, are in fact bikonts.[3]
Relationships within the bikonts are not yet clear. Cavalier-Smith has grouped the Excavata and Rhizaria into theCabozoa and theArchaeplastida andChromalveolata into theCorticata, but at least one other study has suggested that theRhizaria andChromalveolata form aclade.[4]
An alternative to the Unikont–Bikont division was suggested by Derelleet al. in 2015,[5] where they proposed theacronymsOpimoda–Diphoda respectively, as substitutes to the older terms. The name Diphoda is formed from the letters ofDIscoba anddiaPHOretickes (shown in capitals).[suggested singular forms are Opneme-Dipheme respectively][citation needed]
A "classical" cladogram (data from 2012, 2015) is:[6][7]
However, a cladogram (data from 2015, 2016) with the root in Excavata is[5][8][9]
Thecorticates correspond roughly to the bikonts. WhileHaptophyta,Cryptophyta,Glaucophyta,Rhodophyta, theSAR supergroup andViridiplantae are usually consideredmonophyletic,Archaeplastida may be paraphyletic, and the mutual relationships between these phyla are still to be fully resolved.
Recent reconstructions placed Archaeplastida and Hacrobia together in an "HA supergroup" or "AH supergroup", which was a sister clade to the SAR supergroup within theSAR/HA supergroup. However, this seems to have fallen out of favor as the monophyly of hacrobia has come under dispute.
Data related toBikonta at Wikispecies
Media related toBikonta at Wikimedia Commons