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 mitochondria in the ventral view also have a speculative shape, but their shape in the cross-section is not speculative, as I based it on how they appear in Kugrens et al. (1999): Figure 21.
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
