Komma caudata

Komma caudata (L.Geitler) D.R.A.Hill 1991 is a species of unicellular blue-green alga (although the color is actually primarily in the chloroplast, as the rest of the alga is transparent). It belongs to the superclass Cryptomonada, commonly called "cryptomonads" or "cryptophytes," which in turn are included in the phylum Cryptista, within the clade Pancryptista. This clade is closely related to the clade Archaeplastida, which includes Rhodelphia (species of the genus Rhodelphis), red algae (Rhodophyta), glaucophytes (Glaucophyta), picozoans (Picozoa), and finally the plants and green algae related to them (Viridiplantae).

Organism dimensions? 8 to 12 µm long and 4 to 6 µm wide.

Before continuing, I must mention that all the information written here, as well as the diagrams and illustrations, were based on the drawings, micrographs, and information available in these articles:

• Chroomonas and other blue-green cryptomonads. David R. A. Hill 1991. 
• "Chapter 18: Cryptomonads". Brec L. Clay 2015. Pages 809-850. From the Book: "Freshwater Algae of North America (Second Edition)".

Komma caudata. Full diagram. DOTkamina 2025. Based on: Clay (2015) and Hill (1991).

Well, the main diagram (?) depicts several things. In the center, which is the main image, is the anatomical diagram of Komma caudata as if it were a longitudinal section. All the parts have schematic shapes that approximate reality, as well as purely representative colors, which don't necessarily illustrate what the organism actually looks like. The mitochondria and the endoplasmic reticulum (both smooth and rough) are represented speculatively, and it's assumed that they should exist since it's a eukaryotic cell. The Golgi apparatus is also speculative, although it is mentioned that it exists in the anteroventral part. In Hill (1991), Figure 21, it's depicted almost near the contractile vacuole, and I've done the same for my illustrations.

What else is noteworthy? Well, Komma caudata has a comma-like shape, hence the name. It was previously classified as Chroomonas caudata L.Geitler 1924, which is its basionym. The synonym is Chroomonas acuta Utermöhl (1925). In Clay's (2015) illustration, Figure 13A, it is depicted with a very pointed posterior end, but I believe it is smoother. In fact, it was depicted that way in the earlier version of Clay's 2003 work.

Let's talk about the other structures: Komma caudata has two flagella, one short and one long, located on the right wall of the vestibule. The vestibule is a concavity that leads to the digestive zone of a protist, which in this case is the gullet. Both flagella have mastigonemes: the short one has only one row of mastigonemes, while the long one has two rows oriented in different (opposite) directions. The mastigonemes consist of two parts: what I call the "main tubular hair" (to refer to the main structure of the mastigoneme, although this term is not recognized in any of the articles), and the "fine terminal filament". The "fine terminal filaments" also cover the ends of the flagella.

Clay (2015) only "mentions" the nucleus located at the posterior end of Komma caudata, a contractile vacuole at the anterior end, and two rows of ejectisomes, six in each row (it's important to note that neither Clay (2015) nor Hill (1991) specifies the number of ejectisomes; it seems Clay (2015) assigned that number by mere inference or for some unknown reason, but I decided to replicate it. In the earlier version, Kugrens and Clay (2003) listed two rows of five ejectisomes each. In any case, ejectisomes are not easily visible under a light microscope, and the two rows appear to be rare to observe).

Clay (2015) neither mentions nor depicts the nucleomorph that was found according to Hill (1991). The nucleomorph should be located on the ventral side of the pyrenoid, and slightly posterior to it (I have drawn it as if it were "just below" the pyrenoid). In Hill (1991), it is mentioned that the nucleomorph cannot have a well-defined shape, appearing as a diffuse, layered, fibrillogranular region. The nucleomorph is a kind of vestigial nucleus. 

Komma caudata illustration (No labels).

Komma caudata possesses a single large chloroplast containing the biliprotein Cr-phycocyanin 645. It is perhaps the largest of all the organelles, literally occupying the entire dorsal region of Komma caudata. In fact, you can imagine it as a kind of internal backpack or corset-like structure that almost completely surrounds the organism internally. In Clay's (2015) illustration (Figure 13A), I almost got freaked out because it depicted "two apparent chloroplasts," but damn, it's supposed to have only one. Then I realized that what he was trying to represent was the immensity of the chloroplast; it wasn't two, but the same one, but because it was a longitudinal section, they appeared to be two, with the rest of the chloroplast "at the bottom, on the dorsal side of the organism." 

I think in my drawing I've tried to make the immensity of the chloroplast clear. But just in case it's not clear, the cross-sectional illustration clearly shows how much the chloroplast extends:

Komma caudata. Transversal section.

Clay (2015) represents the pyrenoid as a separate structure attached to the chloroplast, but I believe that pyrenoids are, in fact, inside the chloroplasts, and therefore I represent it within them. The only one pyrenoid is surrounded by "several starch granules," which form the "sheath of starch".

Speaking of the cross-sectional view: the one I'm illustrating here is a section of the pink line that's in the main illustration, and it's based on Figures 22 and 23 from Hill (1991). You can only see the gullet, the chloroplast, and the pyrenoid with its starch coat, oh, and two ejectisomas. Consider that the nucleomorph should be located below the pyrenoid region, and the nucleus much further down.

Other organelles: mitochondria, which, according to Hill (1991), have been found as "mitochondrial profiles restricted to the center of the cytoplasm". Therefore, I have depicted some mitochondria oriented towards the center of this alga. The shape and size of the illustrated mitochondria are speculative. Furthermore, I assume there must be few of them, since there is a chloroplast that provides energy to the entire organism. I do not know how many mitochondria there might be.

Komma caudata. Periplast representation.

The illustration at the bottom right in the main diagram (or simply wacth the image above, with your eyes obviously) shows a simplified representation of what the periplast of Komma caudata would look like under an electron microscope. The periplast is like a cell wall, only softer. In Komma caudata, it's made of hexagonal plates. Next to the simplified image is a surface view of a pair of these hexagons with the cytoplasm underneath. Then there is a cross-sectional view of the same section, showing that the plates are arranged like roof tiles. These hexagonal plates are not represented in the other diagrams of the organism.

Well, I guess that is all there is to say. I thought I had finished everything yesterday, but then I noticed an error in the placement of the Golgi apparatus and had to redraw the entire thing again this morning. Uff. I would say it annoyed me, but I actually did it without complaining much. I suppose this is what people call true vocation. I don't know.

As always, these images appear on Wikimedia Commons and anyone can use them for homework, essays, monographs, theses, presentations, constructive critiques, articles, or posts. The use remains noncommercial. I don't think I mentioned this in other posts, but if you see any of my illustrations for sale, contact me at once or report the content, because (I want to gain that money too lmaoo) these illustrations remain free and should not appear on sale. The only requirement I ask for their use is that you mention the authorship: DOTkamina 2025. A fuller credit line could read: “DOTkamina 2025 (based on Clay 2015 and Hill 1991).”

I guess that's all. I'll continue dreaming on that girl.