Pyrenomonas ovalis

This was actually a project I had almost finished and was about to postpone. Well, I don't know if I'll manage to finish it right before 2026, but at least the drawings were complete, and that's what counts. For these diagrams, I used the images and information available in the following two sources, as well as the information written in this blog post:

• "Chapter 18 - Cryptomonads". In: "Freshwater Algae of North America (Second Edition)". Brec L. Clay 2015.
• "Ultrastructure and Systematics of Two New Freshwater Red Cryptomonads, Storeatula rhinosa, sp. nov. and Pyrenomonas ovalis, sp. nov.". Paul Kugrens, Brec L. Clay, Robert E. Lee. 1999.

Having said that, I will begin by stating that Pyrenomonas ovalis P.Kugrens, B.L.Clay & R.E.Lee 1999 (synonym: Rhodomonas ovalis Nygaard 1950) is a species of cryptomonad alga (superclass Cryptomonada, class Cryptophyceae, order Pyrenomonadales, family Pyrenomonadaceae), belonging to the phylum Cryptista in the clade Pancryptista, which in turn is part of the CAM clade, which, along with Pancryptista, also includes Archaeplastida (the algae related to and ancestors of plants).

The cells of Pyrenomonas ovalis (each cell being considered an "independent individual") are oval-shaped and can vary in color from pink to red, due to the presence of chloroplasts. I should mention that, although reddish tones were used in the illustrations, they aren't entirely realistic of the organism in real life, and their use was purely artistic and educational (to make the parts more visible).

The thing is, at first glance it might seem that P. ovalis has two chloroplasts. That's not true! It has a single chloroplast, but it's bilobed. Each lobe is connected by a midline that encloses a starchy membrane, which in turn encloses the pyrenoid. What's unsettling is that the pyrenoid has a ventral invagination that houses a nucleomorph so oddly shaped that it's elongated and fusiform. Oddly shaped, because until now I'd only seen nucleomorphs with more or less oval shapes (well, like misshapen potatoes), but anyway, they resemble organelles that never quite became nuclei. But the nucleomorph of P. ovalis has this strange shape and location.

That, I believe, is the most remarkable feature of this organism. The rest is typical of what you would expect to find in cryptomonad algae. The nucleus is located at the posterior of the cell, the contractile vacuole at the anterior, and the vestibule, with its furrow, connects to a gullet, which houses the flagella. The flagella are located subapically on the right side of the vestibule (this would be in dorsal view; in ventral view, they appear to be inserted on the left side). The ventral flagellum is shorter than the dorsal one and has only one row of tubular hairs, while the longer dorsal flagellum has two rows. The endoplasmic reticulum and Golgi apparatus have speculative shapes. The single reticulated mitochondrion distributed throughout the cell also have a speculative shape, but his shape in the cross-section is not speculative, as I based it on how they appear in Kugrens et al. (1999): Figure 21.

In the case of the mitochondrion, I have tried to represent it according to the established pattern for cryptomonad algae: that it is usually a single reticulated mitochondrion (i.e., as if it were an interconnected network). In the work of Santore and Greenwood (1977), it is indicated that this single reticulated mitochondrion is usually like a network of branches (sometimes thinner than others) that may be concentrated around the gullet. The branches extend throughout the cell, both internally (I would call this the "internal mitochondrial complex") and near the inner side of the plasma membrane (the "peripheral mitochondrial complex").

There are some exceptions to this general form of reticulated mitochondrion (for example, Hemiselmis rufescens has a more worm-like and unbranched mitochondria) (Santore and Greenwood (1977), but unfortunately for Pyrenomonas ovalis, I haven't found any visual information about its mitochondrion in ventral or spatial view across the entire "body" of the organism. There is a micrographic representation in cross-section (Kugrens et al. (1999): Figure 21), which mistakenly suggest that they are individual units, but it's most likely a random cross-section, a piece of mitochondria, from the entire tangled structure that runs through the cell.

The transversal section I've drawn better shows the bilobed nature of the chloroplast. I've also included the thylakoids (those dark lines that create a kind of labyrinth within the chloroplast lobes. The thylakoids are the sites where photosynthesis takes place, by the way). The ventral invagination of the thylakoid, where the nucleomorph is located, is also visible. In cross-section, it appears small, but that's due to the viewing angle; ventrally, its true elongated shape would be visible. Although it's a cross-section, I've also included a "shadow" of the vestibule, but that's just a representation of its location; it wouldn't actually be visible in a cross-section.

I've also illustrated what I imagine a colony of P. ovalis to look like, since Kugrens et al. (1999) mention that it forms palmelloid colonies. Do you know what "palmeloid" means? Because I thought they formed palm-shaped colonies or something. Purely nonsense: palmelloid in this context means colonies whose cells are enveloped in some kind of protective secretion. In the case of P. ovalis, this coating is a mucilage matrix. In Kugrens et al. (1999): Figure 16, the electron microscopy image reveals that the mucilage has a rather irregular and wrinkled texture, like aluminum foil that has been crumpled and folded quite a bit. Although that could be a consequence of the freeze-fracture technique being applied to observe that shape. This technique consists of freezing (fracturing) a biological sample and then depositing a platinum-carbon mixture to build a replica that can be better observed under a transmission electron microscope (Severs 2007). Anyway, I've represented that same texture in my illustration, and my "colony" only consists of 3 specimens... but you can imagine that in real life a colony could include more P. ovalis cells.

Finally, I've also depicted the periplast of Pyrenomonas ovalis. As in other cryptomonads, the periplast is a covering structure of the cell, functioning as a cell wall (although it's more flexible and not as thick), and it consists of two parts: the inner component (made of rectangular plates with rounded corners), and the outermost surface component, which consists only of thin fibrils.

And I think there's nothing more to say about this organism. I just want to mention that these illustrations will be hosted on Wikimedia Commons for free (non-commercial) use, with the requirement that you credit me (DOTkamina 2025). 

And I think that, all things considered, it's a good way to end 2025. I wish I could have done more... but at least I can say that I did, and that I'd like to continue making more illustrations as long as I can. 

I hope this is helpful. Happy new year (づ ◕‿◕ )づ

Goniomonas truncata

Goniomonas appears to be a primitive cryptomonad organism because it lacks chloroplasts, unlike other cryptomonads. It also lacks any other type of plastid or nucleomorph. In all cases, it appears transparent. That's why I liked drawing it: simple and easy to remember.

In the following illustrations, I've depicted the dorsal and lateral views of the organism. The illustrations are based on the following sources:

• "Chapter 18 - Cryptomonads". In: "Freshwater Algae of North America (Second Edition)". Brec L. Clay 2015.
• "Goniomonas truncata (Fresenius, 1858) Stein, 1878". Dr. Martin Kreutz. 2023 (Estimated with WebsiteAge). 

Additionally, I needed to consult other sources of information for the writing of what is written in this entry, which are the following:

• "Cryptic Cryptophytes – revision of the genus Goniomonas".  Maria Sachs, Frank Nitsche, Hartmut Arndt. 2025.
• "Heterotrophic flagellates (Amorpha and Diaphoretiches) in phytotelmata bromeliad (Bromeliaceae)". Poliana Maria Sachertt Mendes, Fernando Miranda Lansac-Tôha, Bianca Ramos Meira, Felipe Rafael Oliveira, Luiz Felipe Machado Velho, Fábio Amodêo Lansac-Tôha. 2019.
• "Morphology, Ultrastructure, and Small Subunit rDNA Phylogeny of the Marine Heterotrophic Flagellate Goniomonas aff. amphinema". Mercedes Martin-Cereceda, Emily C. Roberts, Emma C. Wootton, Elisa Bonaccorso, Patricia Dyal, Almudena Guinea, Dale Rogers, Chris J. Wrighte and Gianfranco Novarino. 2009.
• "The mitochondrial complex in cryptophyceae". U.J. Santore, A. D. Greenwood. 1977.
• "Order Cryptomonadida". Paul Kugrens, Robert E. Lee and David R. A. Hill. In: J. J. Lee, G. F. Leedale & P. Bradbury (ed.), An Illustrated Guide to the Protozoa. 2nd ed. 2002. p. 1111–1125.
• "Ultrastructure and molecular phylogeny of the cryptomonad Goniomonas avonlea sp. nov.". Eunsoo Kim, John M Archibald. 2013.

I was seriously considering postponing writing this, but I really want to finish it and at least try to reach 10 protists and not feel like an empty shell. Let's look at the main image:

I've included two views: dorsal and lateral. I think the dorsal view is easier to understand than the ventral view; I believe the parts are clearer in the ventral view. I don't want it to be obvious that the main inspiration was Clay's diagrams (2015).

The flagella of Goniomonas truncata are of similar length, approximately half the length of the cell, and emerge from the dorsal side of the vestibule. Clay (2015) mentions, however, that one of these flagella has a row of "curved spines" (Kugrens et al. 2002 describe them as "recurved"), and a row of fine "non-tubular hairs" on both flagella. Indeed, that is how I have depicted them in the illustrations, although you may need to enlarge the images to see that detail.

In Clay's diagrams (2015, Figure 3A), it is represented with 8 ejectisomes, but Kreutz (2023) mentions that there are only 6, and according to the micrographs in that reference, there appear to be 4 ejectisomas larger than the other 2 (see Figures 4a and 4b of the reference), with the 4 facing ventrally and the other 2 facing dorsally. However, this is just my observation, and I don't know if it's a real anatomical feature, since I don't see that arrangement in Figures 2 and 3 of the same reference. I have represented it as mentioned in Kreutz (2023) and as visualized in Kreutz (2023, Figures 4a and 4b).

I think many agree that Goniomonas appears to be an ancestral cryptomonad organism and that's why it doesn't have chloroplasts or any other type of plastid. It has several food vacuoles, which form each time the organism ingests bacteria, so their number and size vary depending on the size and quantity of bacteria ingested. The nucleus is located dorsally in the center. And in Clay (2015), it is not represented with anything else, giving the appearance that it is actually simpler than other cryptomonads.

Of course, mitochondrion, Golgi apparatus, rough and smooth endoplasmic reticulum were represented, but their shapes, sizes, and colors are merely speculative, and I assume they must exist because this organism is a eukaryote, and these organelles are technically present in "most eukaryotic cells." Ribosomes are also represented, in high concentration near the rough endoplasmic reticulum, and dispersed and a lighter purple hue (like small dots) throughout the cell.

In the case of the mitochondrion, I have tried to represent it according to the established pattern for cryptomonad algae: that it is usually a single reticulated mitochondrion (i.e., as if it were an interconnected network). In the work of Santore and Greenwood (1977), it is indicated that this single reticulated mitochondrion is usually like a network of branches (sometimes thinner than others) that may be concentrated around the gullet. The branches extend throughout the cell, both internally (I would call this the "internal mitochondrial complex") and near the inner side of the plasma membrane (the "peripheral mitochondrial complex").

There are some exceptions to this general form of reticulated mitochondrion (for example, Hemiselmis rufescens has a more worm-like and unbranched mitochondria) (Santore and Greenwood (1977), but unfortunately for Goniomonas truncata, I have not found any information about its mitochondrion. In the case of the illustration of Goniomonas here, I have chosen to represent it as less extended and with somewhat broad mitochondrial branches, but I believe that in reality it should be more tangled and extensive.

Clay (2015) mentions that Goniomonas truncata only has one furrow and does not connect to any gullet as occurs in other cryptomonads. It also mentions that bacterial ingestion occurs through phagocytosis, via a structure known as an "infundibulum." Neither of these structures is depicted in Clay (2015).

The descriptions I found of the furrow and infundibulum are limited, mainly because I don't have enough visual references. But I did what I could. According to Kugrens et al. (2002), the furrow is ventral and connected to the vestibule. The furrow has a stoma on its posterior end (I understood this to mean "at the posterior end," and there is a reference to this in Cryptomonas tetrapyrenoidosa, see Kugrens et al. (2002), Figure 4). The infundibulum is described as being located "on the left side" of the cell. Kugrens et al. (2002), Figure 13, shows a micrograph of Goniomonas truncata that conveniently indicates the furrow and infundibulum. 

Considering that the flagella are located on the dorsal side of the vestibule, then in that figure we are viewing the organism from the ventral side, and the furrow appears to be a large structure that runs along a good portion of the ventral area, I believe roughly halfway, although that is just a rough estimate. In Clay (2015), the diagrams also have an unnamed notch on the ventral side, which I suppose could represent the furrow. The infundibulum in Figure 13 appears as a hollow, which obviously extends deeper into the cell, but its length is not indicated. 

Kim and Archibald (2013) mention that the infundibulum of G. truncata is "narrow and located near the anterior left corner," which is basically what I had already mentioned: that it is "located on the left side." I don't know how narrow it actually is; I have represented it as roughly the same width as the furrow, although shorter in length. In Martin-Cereceda et al. (2009), it's mentioned that the infundibulum of G. truncata could actually be interpreted as a cytopharynx, but in my representation, I call it an "infundibulum" anyway.

And what else can I say about this? Well, nothing more. The rest of the cell is occupied by food vacuoles. I could swear I've already mentioned that somewhere. I think I have nothing more to add. Oh yes, except that this was supposed to be published at Christmas, but I got delayed because I was terribly depressed to see that the furrow was ventral and not "dorsal" as I was originally representing it, and I had to redraw the diagrams and names again to make them match. That said, the part about the infundibulum and furrow is almost speculative, because I don't know their true morphology and size. It's there as a research reference for future projects.

Of course, Goniomonas truncata is transparent and doesn't have that many colors in real life. The ones shown here are for illustrative and educational purposes. I've tried to avoid using overly bright colors that might lead to misunderstandings. The images are free to use and are available on Wikimedia Commons. As always, the only requirement is that you credit me if you use, reference, or modify any of the images: DOTkamina 2025.