| Divimonas | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Order: | Ancyromonadida |
| Genus: | Divimonas Barkhouse, Eglit, Weston & Simpson 2025 |
| Species: | D. melba |
| Binomial name | |
| Divimonas melba (Simpson & Patterson 1996) Barkhouse, Eglit, Weston & Simpson 2025 | |
| Synonyms | |
Ancyromonas melba Simpson & Patterson 1996 | |
Divimonas is agenus offlagellates containing the single speciesDivimonas melba, found in sediments fromhypersaline lakes andantarctic material. It belongs to theancyromonads, a group of small flagellated microbes with a basal position in the eukaryotic tree of life. The species was initially classified within the genusAncyromonas, but through genetic analysis it was determined to belong to a different evolutionary branch from that of any previously known ancyromonad.[1]
The name of genusDivimonas is a reference to thedivi-divi (Libidibia coriaria), the national tree ofCuraçao, the island where the species was first successfully isolated. It is followed by-monas (from Greek μονάς, meaning 'unit'),[1] a common suffix for single-celledprotists.[2] The epithetmelba has no specified etymology.[3]
Divimonas melba is a species of single-celled free-livingflagellates. Their ovoid cells (4.2–4.6 μm in length, 3.4–3.7 μm in width) are flattened on thedorsal andventral sides with the ventral side hollowed, sometimes with a typicalancyromonad "bean shape" due to an indented left edge and a rounded right edge. A ventral groove originates from the anterior ventral end (rostrum or "snout"), and runs longitudinally down the surface, continuing as a ventral crease rather than a depression.[3] The rostrum contains spherical bumps that are presumablyextrusomes.[1]
Each cell has twoflagella. The posterior flagellum (9.7–10.5 μm long) emerges from the anterior end of the ventral groove and is held under the cell and used to attach to surfaces. The anterior flagellum (3.8–4.7 μm long) emerges from a small depression at the anterior dorsal end, and sweeps back and forth in front of the cell. Both flagella have a similar thickness.[1][3]
D. melba has been observed performingasexual reproduction through cell division, in which the daughter cells are last separated at the posterior end. It has not been observed feeding, but probabledigestive vacuoles have been observed, presumably withbacteria.[1]
Divimonas melba has been found inhypersaline lakes from the Shark Bay region ofWestern Australia[3] and from the Caribbean island of Curaçao.[1] It has also been observed in material obtained fromAntarctica,[4] meaning it may not be restricted to hypersaline environments.[3]
Cells of this species were originally described in 1996 byprotistologistsDavid J. Patterson and Alastair G. B. Simpson, who discovered them in two hypersaline lakes in the Shark Bay region of Western Australia. They described them as a new species,Ancyromonas melba, due to the cells being strongly reminiscent ofAncyromonas sigmoides in severalmorphological features. As such, it was classified in theAncyromonadida, a group of small eukaryotes with a basal position in eukaryotic evolution.[3] However, this classification remained uncertain, as its morphological features were still very different fromA. sigmoides and all other ancyromonads.[1]
In 2025, the first molecular data ofA. melba was obtained. Cells ofA. melba were isolated from salt crust samples belonging to a hypersaline pond nearFort Beekenburg, Curaçao. TheirSSU rRNA gene wassequenced. Through aphylogenetic analysis performed with this gene, it was revealed that its evolutionary position is not within any known genus of ancyromonads, but as a new separate branch. Consequently, the species was transferred to a new genus and renamed asDivimonas melba. The genusDivimonas is consideredincertae sedis within the order Ancyromonadida, as it is unclear to whichfamily it should be assigned.[1]
