Another one of the strange organisms I've been illustrating. I find the name funny because no matter how I look at it, it sounds like "pig." The name "biforma" is because it has two forms, indeed (obviously lol). Unlike Subulatomonas, which I was too lazy to illustrate, I actually illustrated both forms of P. biforma. I had it all ready when I realized a structure was missing and I had to redo it—what a pain!
Reminder (da f___ng reminder) that the images of the organism are free to use under CC BY-SA 4.0, non-commercial, attribution required (DOTkamina 2026).
If you've ever stumbled across this obscure site, you'll know I'm a ₗₐzy bᵤₘ, so I'll take advantage of the fact that this organism is also a breviate (like Subulatomonas tetraspora), and copy the exact same taxonomic description, varying it for Pygsuia biforma. I hope you can forgive me. Or well, never mind, I already did it before with cryptomonad algae. So, idc.
Pygsuia biforma is not in AlgaeBase, which surprised me. It is in NCBI Taxonomy. The organism belongs to the family Pygsuidae, order Breviatida, class Breviatea. The truth is, I've only found the name "Pygsuidae" on Wikipedia. NCBI Taxonomy directly includes P. biforma as part of 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)...
I have relied mainly on two articles for the creation of the illustrations of this organism, as well as for writing its description:
- "Phylogenomics demonstrates that breviate flagellates are related to opisthokonts and apusomonads". Matthew William Brown, Susan Sharpe, Jeffrey D. Silberman, Aaron A. Heiss, B. Franz Lang, Alastair Simpson, Andrew J. Roger. Proceedings of The Royal Society B. 280(1769):20131755. DOI: 10.1098/rspb.2013.1755. 2013.
- "A SUF Fe-S Cluster Biogenesis System in the Mitochondrion-Related Organelles of the Anaerobic Protist Pygsuia". Courtney W. Stairs, Laura Eme, Matthew W. Brown, Cornelis Mutsaers, Edward Susko, Graham Dellaire, Darren M. Soanes, Mark van der Giezen, Andrew J. Roger. Current Biology. Vol. 4, Issue 11. 1176-1186 pp. 2014.
Well, this organism is certainly interesting. Uhm... I'm sure it won't seem so interesting to me once I explore its taxonomic relatives further. I've represented its two main forms: adherent and swimming.
In both forms, we can see that the organism has a
nucleus (I assume it also has a nucleolus, but
Brown et al. 2013 don't mention this organelle, so I've decided not to represent it); an elongated, double-membrane
mitochondrial-related organelle (
MRO) (usually only one) without obvious cristae, one end of which is close to the basal bodies;
bacteria ingested in food vacuoles (I've represented two "morphs"—the more oval vacuoles are inspired by
Brown et al. 2013, and the comma-shaped ones are based on the micrographs by
Stairs et al. 2014); and
starch-like granules (bodies), which
Brown et al. (2013) mentions that there are "several," although only one is indicated and observed in the micrograph Figure 1 of that article... but I have depicted more.
Of course, we mustn't forget the
basal bodies (the structures that attach to the flagellar microtubules), which are at an obtuse angle. There is also a
Golgi apparatus near the anterior end of the MRO. I have depicted it almost elongated, as can be seen in
Brown et al. (2013): Figure 1e. Oh, and I almost forgot: there's also a "
dorsal microtubular fan" (
MDF), which surrounds the back of the anterior basal body and appears to continue close to the MRO (see
Brown et al. 2013: Figure 1e). I could have sworn the MDF was visible in the image, but looking at it again, I've drawn it very thin... which is close to reality, but it's still not very noticeable at first glance. I apologize for any potential eye strain.
I almost forgot this too: the endoplasmic reticulum is speculatively shaped, and I assume it exists because it's a nearly ubiquitous structure in all eukaryotic cells. The rough endoplasmic reticulum has ribosomes (those light-colored, stuck-together dots in the image), but I assume ribosomes are also dispersed throughout the rest of the cell. The smooth endoplasmic reticulum doesn't have nearly as many ribosomes. In this illustration, as well as in all the previous ones of other organisms, I've always depicted the smooth endoplasmic reticulum as having shorter and somewhat wider bodies than the rough endoplasmic reticulum, but that's just my convention to try and make the difference more noticeable. In real life, both forms can be intertwined, have the same width, and not be noticeable as two completely separate structures. I think I should have included that caveat for the others as well.
That said, let's get to the morphs. The cell in its adherent form is pear-shaped. Dimensions: 8.5–18.5 mm long and 5–8 mm wide. It has two flagella. The anterior or apical flagellum is the longer one, 8 to 30 µm. The posterior flagellum is (usually) shorter, measuring less than the cell itself. It's inserted subapically and closely associated with the cell surface, hence why I've drawn it attached to the cell, in the region where the MRO would be underneath. Anatomically It's very likely that the spatial arrangement I've chosen for the illustration won't always be the case.
When the cell is actively gliding in an adherent state, it develops prominent,
filose pseudopodia, which form at the anterior end of the cell. For a moment, I was freaking out because in
Brown et al. 2013: Figure 1a, more pseudopodia are shown not only at the anterior end but also along one side of the cell, extending to the posterior end. But apparently, pseudopodia can form at the posterior end and on the rest of the cell (
Brown et al. 2013: Supplementary Data Figure S6 B). The only difference is that the posterior pseudopodia are more prominent and appear to be branched. I haven't represented that property because I just found out about it. And honestly, I don't think I'm going to make a new image representing that possible state. Sorry!
Finally, the other state is the swimming cell form. Here, the cell has a more rounded or elongated shape (not obviously pear-shaped; I depicted it as a somewhat narrow oval, but not quite pear-shaped). Cells in this form are 8.5–13 mm long and 3.7–5.3 mm wide. The anterior or apical flagellum is "long", 8.5–28 mm long, and inserted apically. The main difference lies in the posterior flagellum. In the adherent form, this was short and attached to the cell surface, but in the swimming form, the posterior flagellum is 50% longer than the anterior flagellum (16–37 mm long), and, although still directed posteriorly, it is more "free," meaning it is not as tightly attached to the cell surface.
That's really all there is to say about this organism.
ヾ(^ ^ゞ
I hope this information and the images are helpful. Don't forget to give credit, and read the original articles where I got all this information if you want more technical details and so on.
I'm signing off now 'cause I want to upload this to Wikimedia Commons quickly.
(∩♡°ω°)⊃
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