Aaaah, my mind feels foggy and my ribs are aching (not in the way you might imagine) because I just played Roblox's Hypershot game for about an hour, I think? But anyway, it's time to get back to doing something productive.
Reminder that the images of the organism are free to use under CC BY-SA 4.0, non-commercial, attribution required (DOTkamina 2026).
That said, I'll begin by providing the taxonomic context. Subulatomonas tetraspora is an unusual organism, in the sense that its position in the phylogeny was completely unfamiliar to me. In fact, on AlgaeBase it's listed as part of "Eukaryota unassigned," so it's playing coy. According to the English Wikipedia, the organism belongs to the family Breviatidae, order Breviatida, class Breviatea.
The class Breviatea, the breviate amoebas, are strange amoebas that lack mitochondria (instead, they have structures similar to them, as you'll see later), have two flagella, and a metabolic style adapted to low oxygen (anaerobic). They are unusual because their taxonomic placement is uncertain.
The class Breviatea is included in the clade Obazoa, a group of eukaryotes that also includes Apusomonadida (amoebas that do have mitochondria, although some have modifications that resemble those of Breviatea) (Torruella et al. 2018) and Opisthokonta (amoeboid eukaryotes that share the characteristic of moving with the aid of a single posterior flagellum. In contrast, Breviatea and Apusomonadida move with at least one anterior flagellum. Opisthokonta is notable for encompassing organisms related to the ancestors of animals and fungi, as well as the animals and fungi themselves).
Obazoa is grouped with Amoebozoa (the "common amoebas" as such) in the clade Amorphea or Unikonta (common characteristic: a single flagellum) (Spiegel 2016). Amorphea is included in the clade Podiata (which would include Amorphea and CRuMs). Podiata is finally included in the large domain Eukaryota, related to other clades I've already covered and others I hope to discuss later, such as Metamonada (Giardia lamblia) or Diaphoretickes (which includes Archaeplastida (plants and relatives of plant ancestors), Pancryptista (which includes cryptomonad algae), the SAR group, and so on)...
.............. And many more.
Fuck, I've barely scratched the surface of eukaryotic taxonomy.
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But anyway, back to Subulatomonas tetraspora. For the illustrations and the text here, I based them on a single article, which is where it is described in more detail: "Subulatomonas tetraspora nov. gen. nov. sp. is a Member of a Previously Unrecognized Major Clade of Eukaryotes", by Laura A. Katz, Jessica Grant, Laura Wegener Parfrey, Anastasia Gant, Charles J. O’Kelly, O. Roger Anderson, Robert E. Molestina and Thomas Nerad. Protist, Vol. 162, Issue 5. 762-773 pp. 2011. https://doi.org/10.1016/j.protis.2011.05.002
The organism has several morphologies (amoeboid, gliding, swimming, settling), but I was too lazy to illustrate them all, to be honest. I opted for the gliding form, and that's the form I've depicted in the illustrations.
The organism has characteristics typical of a standard eukaryotic cell: a nucleus with a central nucleolus, and a Golgi apparatus (which in this organism is described as "small" and without observable microtubules in its region). The dimensions of the entire cell (without flagella or pseudopodia) are usually 5 to 10 µm long and 3 to 5 µm wide.
As I mentioned, it belongs to the class Breviatea, organisms that lack true mitochondria. S. tetraspora has what the authors believe are possibly "hydrogenosomes." There are a few of them, and they have a double membrane. Hydrogenosomes likely evolved from mitochondria. The difference is that they lack cristae (which should mean that no texture is visible inside them, but in S. tetraspora a texture is observed, which I have represented as darker areas within the hydrogenosomes), and they function in an anaerobic environment, releasing hydrogen (H2) as a waste product.
S. tetraspora is microaerophilic btw (meaning it is not completely anaerobic, but requires very little oxygen to thrive; amounts close to normal are poisonous to it).
Another peculiar feature is the food vacuoles, which contain the remains of bacteria in the process of digestion, which is what they eat (I have represented these digesting bacteria as very dark and irregular areas within the food vacuoles). The unsettling thing is that there are also bacteria within the cytoplasm, free-floating (in the illustration I have labeled this "Bacteria"). I suppose these must be ingested bacteria that have not yet been incorporated into a food vacuole.
The endoplasmic reticulum has a speculative shape, and I represent it as such because I assume it exists in all eukaryotes except for exceptions that should be noted. However, this is just an illustration, and it's worth noting that the endoplasmic reticulum could be less "branched," perhaps more extensive throughout the cell, with narrower sacs and tubules.
Finally, regarding external appearance: The cell is awl-shaped, with a "neck" approximately 6 µm long, which "extends along a substantial portion of the single flagellum and reappears when the flagellum moves to a new location." This leads me to believe that the neck acts as a "cover" for part of the flagellum, but I'm not certain. In the illustration, I've depicted the single flagellum emerging from the tip of the neck, but it assumes that it continues within the neck and is eventually connected to a basal body that appears to be located not at the tip of the neck, but rather near its base on the main cell body (see Katz et al. 2011, Figure 2D). The flagellum measures 6 to 12 µm in length. The flagellum is located anteriorly and is used for movement.
I have represented the basal body with a standard 9+0 microtubular arrangement (9 peripheral triplets and no central microtubules). This contrasts with the 9+2 arrangement of the flagellum, which has 9 peripheral doublets and two central microtubules; this arrangement is not shown. Technically, the illustration represents S. tetraspora in a "longitudinal" view (although it is not a cell section), and therefore the microtubules of the basal body and those of the flagellum should appear as closely packed hairs.
However, I have chosen to represent the microtubular arrangement of the basal body in a cross-section to highlight the 9+0 arrangement. This assumes that the transition from 9+0 (basal body) to flagellum (9+2) does not occur literally at the tip of the neck, but at some intermediate point, I believe slightly closer to the cell body. Honestly, I'm not sure; the article doesn't mention anything about it either, which is why I haven't shown that connection.
Besides the flagellum, in the gliding form, which is the one I've shown, there are a series of small pseudopodia (cytoplasmic extensions) in the neck area, and another large pseudopodia at the rear. It seems that these pseudopodia don't exist in the swimming form; in the amoeboid form, they do exist, but they're distributed throughout the cell, very long, and the flagellum "disappears"—or rather, it seems to be reabsorbed. In the forms with the flagellum present, swimming or gliding, the neck also appears.
Anyway, I think that's all I had to say about this organism. The organism is most likely transparent and should appear grayish. You know what that means: the colors I've used in these illustrations serve more of an educational purpose and don't actually represent reality. That said, I hope you liked this information and found it useful.
Goodbye.
