Cryptomonas obovata Skuja 1948... and notes on Cryptomonas morphs

Well, I don't expect to have much to say about this one, to be honest, except that I've noticed some details that were perhaps missing from the other Cryptomonas curvata illustration I published back in 2025. Damn, that year sounds so far away, and it's already February 2026. When will it be Christmas again?

The following illustrations depict Cryptomonas obovata Skuja 1948, as the name is recorded on AlgaeBase. I have shown it in ventral view. The images are free to use and are also available on Wikimedia Commons. Of course, commercial use of these images is not permitted, nor is their use without proper attribution. "DOTkamina (2026)" is sufficient.

There are two main sources I used as a basis for creating the illustration of this organism:

• "Cryptomonas obovata Skuja, 1948". Martin Kreutz, 2021. Real Micro Life.
• "Chapter 18 - Cryptomonads". Brec L. Clay, 2015. Freshwater Algae of North America (Second Edition). Academic Press.

Btw, that chapter of "Cryptomonads" is even haunting my dreams. Clay, Lee, Hill, Andersen, Kugrens etc., seem to be the experts on cryptomonad algae; they've been researching these organisms since the past century (That's an exaggeration, but... well, you know what I mean). It would fill me with uncertainty, humility, joy, and a touch of fear if they were to see the images I create.

For the design of the flagella, I relied on this article: "Ultrastructural variations in cryptomonad flagella", by Paul Kugrens, Robert E. Lee, Robert A. Andersen, 1987. The design of the mitochondrion is speculative, but it is based on what is said in Santore and Greenwood (1977). I will explain it later.

Cryptomonas obovata follows a similar anatomical scheme to that of Cryptomonas curvata, which I illustrated earlier. The first noticeable difference is in its shape: Cryptomonas curvata could be oval-shaped but slightly more elongated than C. obovata, in addition to having a slight curve at its posterior end.

The second difference, and the one I find most unnerving, is the absence of pyrenoids. Instead, it has numerous starch granules distributed throughout the cell, although Kreutz (2021) mentions that these are located "beneath the chloroplasts." In microscopic photographs (see Kreutz (2021): Figures 1 to 4), these starch granules are clearly visible in both ventral and dorsal views. In my representation, I have chosen to depict them as being beneath the chloroplasts—in other words, "covered" or "hidden" by them. But you should consider that in real life, this property wouldn't be so obvious. Let's not forget that C. obovata has two chloroplasts.

There's another important aspect I should mention: some species within the genus Cryptomonas, according to Clay (2015), can have two distinct morphotypes in their life cycles: the cryptomorph and the campylomorph. I'd say this is a bit poorly worded, because at first glance it implies that it occurs "in all Cryptomonas species," but a quick review of the article by Hoef-Emden and Melkonian (2003) shows that this isn't always the case. Some species do indeed exhibit both morphotypes (cryptomorph or campylomorph), while other species only express one of the two (or, based on current research, it's assumed that only one morphotype occurs in these species because the other simply hasn't been found or observed).

So, briefly, using Clay's (2015) description: the cryptomorph consists of cells that are more or less rounded or oval in shape. These cells are protected by the periplast (a structure that performs a function similar to that of the cell wall in plant cells). The periplast has two layers: the inner periplast component (which in the cryptomorph consists of rounded or oval plates), and the surface periplast component (which in the cryptomorph is made of a thin layer of fibrils).

In the cryptomorph, the plastidial complex (the set of cellular plastids) is generally made up of two chloroplasts, with two pyrenoids not traversed by thylakoids, and two nucleomorphs, one between the nucleus and the pyrenoids. The furrow of the cryptomorph is "complex," possessing a stoma.

The campylomorph was considered for some time to be such a distinct morph that individuals with this morph were considered species in different genera of Cryptomonas. Formally, Campylomonas and Chilomonas. Now that it's known that the forms of both genera are actually the campylomorph, an alternative to the cryptomorph of Cryptomonas, they are considered synonymous where applicable.

But let's see: using again Clay (2015): the campylomorph is first different from the cryptomorph by having a more "sigmoid" cell shape; I would describe it, in simple terms, as a somewhat oval, flattened cell shape with varying degrees of elongation and curvature. More importantly, the periplast may be composed solely of the inner periplast component, simply a layer without shaped plates. The surface periplast component may be absent, but if present, it would be made of fibrillar material or heptagonal "scales."

The campylomorph generally has the same plastidial complex structure as the cryptomorph. The most noticeable difference is seen in the furrow, which lacks a stoma. In addition, it also has a scalariform furrow plate, a structure similar to the furrow plate that, in the campilomorph, resembles a ladder. In the cryptomorph, this furrow plate is only fibrous. I haven't depicted the furrow plate in the illustrations of this species. Finally, the vestibulum in the campylomorph also has a "vestibular ligule," a kind of extension that covers a small portion of the vestibule.

My state right now.

But anyway, those would be the main differences between the cryptomorph and the campylomorph of a Cryptomonas species. Now, in which species exactly, and in which ones only a single morph has been observed... hell, who knows?

According to the article by Hoef-Emden and Melkonian (2003), and comparing it with the information in Clay (2015), the cryptomonad species in which only the cryptomorph was found are: C. ovata, C. obovata (the species I illustrated in this post), C. phaseolus, C. tetrapyrenoidosa, and C. erosa. Clay (2015) also mentions C. ozolinii Skuja 1939 as a cryptomorph, but Hoef-Emden and Melkonian (2003) already indicate that it is actually a synonym of C. pyrenoidifera Geitler 1922 emend. Hoef-Emden and Melkonian (in Hoef-Emden and Melkonian (2003), this synonym is written simply as "C. ozolini Skuja"). C. pyrenoidifera exhibits both morphs, cryptomorph and campylomorph.

Similarly, considering Hoef-Emden and Melkonian (2003) and Clay (2015), the species where, conversely, only the campylomorph was found are: C. platyuris and C. marssonii. Clay (2015) also mentions C. rostratiformis Skuja (omitting the "1950"), which would actually be a synonym of C. curvata Ehrenberg 1832. I had illustrated C. curvata as campylomorphic, but according to Hoef-Emden and Melkonian (2003), it also has the cryptomorph.

There is a problem with C. reflexa. First, it should be noted that Clay (2015) mentions C. reflexa Marsson (syn. Campylomonas reflexa Hill). In AlgaeBase, the closest taxon to the one mentioned is C. reflexa (M.Marsson) Skuja 1939, but I'm not certain. Hoef-Emden and Melkonian (2003) mention C. reflexa Skuja (1939), which may in fact be the same as C. reflexa (M.Marsson) Skuja 1939 in AlgaeBase (they also appear in the same original publication). In any case, Hoef-Emden and Melkonian (2003) indicate C. reflexa as another synonym of C. curvata, and therefore, it would have both cryptomorph and campylomorph. C. reflexa has about five names in AlgaeBase, and all of them are in an "unstable" state, meaning they are not fully accepted.

C. marssonii Skuja 1948 does have only a campylomorph (or rather, only that morph has been found), according to Hoef-Emden and Melkonian (2003). The problem is that this name is currently being debated...

But anyway. I think that covers the important points regarding the morphs.

Returning to Cryptomonas obovata, it's established that it only has the cryptomorph. Based on the general characteristics of the cryptomorph, I have represented its furrow with a stoma. The vestibule lacks a vestibular ligule. There are two nucleomorphs, one on each side of the nucleus.

The main difference from the general scheme of the cryptomorph is that C. obovata does not have pyrenoids; instead, it has those starch granules I mentioned earlier. The ejectisomes "envelop" the entire gullet. This is something that also occurs in other Cryptomonas species. I mention this because in the illustration of C. curvata I did some time ago, I didn't depict the ejectisomes surrounding the entire gullet. Why? For better visibility... I suppose. The contractile vacuole is located behind the chloroplasts and near the anterior region, according to what I see in Kreutz (2021). I haven't represented the periplast and its components.

I have drawn the endoplasmic reticulum, Golgi apparatus, and the single reticulated mitochondrion. The shapes of these structures are speculative. In the case of the mitochondrion, it's a predicted reticulated shape based on what Santore and Greenwood (1977) explains, where it's mentioned that Cryptomonas has a single mitochondrion with numerous branches distributed throughout the cell, concentrated in areas like the gullet. It's assumed that these mitochondrial branches should have different thicknesses in various sections, but in my drawing, the width of these branches is almost uniform.

Finally, the flagella of C. obovata are of type 1 flagella according to Kugrens et al. (1987): the long (dorsal) flagellum has two opposing rows of mastigonemes, each with a single terminal filament. The short (ventral) flagellum also has a single row of mastigonemes, each with two terminal filaments of different lengths. Additionally, there are approximately three terminal hairs at the end of the dorsal flagellum.

Both the mastigonemes and the additional filaments and hairs can only be seen with an electron microscope. Don't expect to see them with a light microscope. Even the flagella are sometimes difficult to see with a light microscope. I almost forgot: both flagella are located on the right side of the vestibule. That's from a dorsal view. In a ventral view, they appear to be on the left, but that's just an illusion!

I could swear there was more to say, but the truth is I went off for a while to... I don't know, do something, the thing is I don't remember anymore. I hope I've covered everything.

Oh right, I almost forgot... the maupas bodies! Those two funny things way behind the chloroplasts and starch granules. C. obovata only has two maupas bodies. I don't know if you know this, but all the colors in these drawings are merely schematic and for educational purposes, and don't necessarily correspond to what you can see in real life. However, according to the images in Kreutz (2021), maupas bodies can be seen under a microscope as two shiny structures. What are they for? .... HAH, who knows?

Cryptomonas curvata = Campylomonas rostratiformis

The first time I drew this organism, I thought I was drawing a rare species. Then I carefully read the synonymy history, and no, what I thought was Campylomonas rostratiformis is now Cryptomonas curvata. I'm well aware of the tensions in the taxonomic world and how they fight over authorship. Sometimes that makes me distrustful. The scientific world can be cruel at times.

Anyway, I'll include below the list of all the synonyms registered for Cryptomonas curvata in AlgaeBase. Curiously, "Campylomonas rostratiformis" isn't listed. That's how it was proposed by Clay in 2015. Later, when I tried to find reference micrographs for the species, only "Cryptomonas curvata" appeared, and that's when I discovered that the current taxonomic decision (at least as of the date of this post, December 14, 2025) is to maintain that name, as a species belonging to Cryptomonas.

I based this drawing on the following articles and sources. Additionally, I obtained the text information in this blog from the first three sources:

• "Chapter 18 - Cryptomonads". In: "Freshwater Algae of North America (Second Edition)". Brec L. Clay 2015.
• "An ultrastructural survey of cryptomonad periplasts using quick-freezing freeze fracture techniques". Paul Kugrens and Robert E. Lee, 1987.
• "Ultrastructural variations in cryptomonad flagella". Paul Kugrens, Robert E. Lee, Robert A. Andersen. 1987.
• "Light microscopical observations of the sigmoid species of the genus Cryptomonas Ehrenberg (Cryptophyceae) and their eventual pyrenoids". Pavel Javornický. 2014.
• "The phytoplankton community (except Bacillariophyceae) of Lake Abant (Bolu, Turkey)". Abuzer Çelekli, Olcay Obali, Okan Külköylüoğlu. 2007.
• "Cryptomonas rostratiformis". Protist Information Server.
• "Cryptomonas". PhycoKey. University of New Hampshire.

Ah, and the synonims list (.づ◡﹏◡)づ, according to AlgaeBase:

Homotypic synonym:

• Cryptomonas ovata var. curvata (Ehrenberg) Lemmermann 1903

Heterotypic synonyms

• Cryptomonas rostrata O.V.Troitzkaja 1922
• Cryptomonas rostrata Skuja 1948
• Cryptomonas rostratiformis Skuja 1950
• Cryptomonas lilloensis W.Conrad & H.Kufferath 1954.

And don't forget about Campylomonas rostratiformis. I saw that name first in Clay (2015), but it's termed as "Campylomonas rostratiformis Hill 1991" in Çelekli et al. 2007.    

Full anatomical representation of Cryptomonas curvata (Campylomonas rostratiformis).

                              

Clay (2015) mentions that it is the largest cryptomonad species, with the following dimensions: 45 to 80 µm long, 16 to 40 µm wide, and 14 to 24 µm deep. He mentions that the posterior part of the Cryptomonas curvata cell (which he refers to as Campylomonas rostratiformis in the article, page 837) is slightly curved, and this is very evident in his illustration of the organism (Figure 7B). However, in the micrographs, I don't see it as so evident, nor can I discern this curvature (Figures 8A-B and 9B). The micrograph on AlgaeBase does show this curvature of the posterior region. Nevertheless, I have included this characteristic in the main drawing (ventral view).

Cryptomonas belongs to the family Cryptomonadaceae, which is part of the superclass Cryptomonada, within the phylum Cryptista, clade Pancryptista, which in turn is part of the CAM clade. The CAM clade encompasses not only Pancryptista but also Archaeplastida, the group that includes algae related to and ancestors of plants.

Anyway, in the main image, I've shown the ventral view of the organism, and below it on the left, the anterior view. On the right, there's a simplified recreation of what the organism would look like unsectioned, as if viewed under SEM. Please note that all colors used here are for illustrative and educational purposes only and may not necessarily correspond to the actual colors. However, Cryptomonas curvata is an alga that naturally appears reddish-brown due to its chloroplasts. According to Protist Information Server, the color range varies from green, through turquoise/blue-green, to brown, and even rarely red.

                                              

Cryptomonas curvata, ventral view illustration.

What can I say about this organism? Let's start with the ventral view: the most ventral part would be the vestibule, which connects to a gullet (a "digestive system," although it's an organelle; remember, it's just a single cell). The vestibule has a slit that faces downwards (towards the posterior region), known as the "furrow." The furrow is oriented slightly to the left. "Hey DOTkamina, but in the drawing it's oriented to the right." Yes, that's because the furrow faces to the left if you were viewing the cell dorsally. In ventral view, it will point to the other side (the left). I don't know why they always describe how it looks in dorsal orientation if the illustrations are ventral. It's confusing.

Slightly parallel and adjacent to both sides of the gullet are two large, reddish-brown chloroplasts. The chloroplasts occupy almost the entire length of the organism. According to Javornický (2014), these chloroplasts may sometimes be joined by a narrow dorsal isthmus. He also mentions that "6 pyrenoids should be typical for the species." Clay (2015) only states that there are "several" pyrenoids. I depicted 6 pyrenoids, 3 for each chloroplast. Of course, each pyrenoid is encased in a starchy sheath, presumably made of granules.

Among other features, the chloroplasts enclose a nucleus with a nucleolus at the rear of the cell (I'm not sure why I mention this; most nuclei in eukaryotic cells have a nucleolus). Around the nucleus, I have depicted the rough endoplasmic reticulum (with dots representing ribosomes. It's assumed they are more concentrated there, but are also distributed throughout the cell), and the smooth endoplasmic reticulum. I have also depicted the Golgi apparatus and a single, reticulated mitochondrion. The shape, number, and size of these structures are purely speculative, and I have done so to emphasize the eukaryotic nature of the organism. It is known that these structures "should" exist.

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). I haven't found exact information on the mitochondrion of Cryptomonas curvata, but in Santore and Greenwood (1977) the spatial arrangement of the mitochondrion of Cryptomonas sp. (undetermined species) is showed. And that would be the inspiration for the mitochondrion of Cryptomonas curvata in this drawing. The width of the mitochondrial branches in this illustration is very homogeneous, but keep in mind that in reality they could be wider in some areas and thinner in others.

                                                              

I will briefly mention the presence of a single contractile vacuole in the anterior portion. 

With that said, let's move on to the last interesting part of Cryptomonas curvata (Campylomonas rostratiformis): the flagella. Two are identified: one short and one long. According to Kugrens et al. (1987) (Figures 9 to 11), both flagella have a single row of mastigonemes, but the structure varies. In the long flagellum, each mastigoneme has only one terminal filament. In the short flagellum, on the other hand, there are two terminal filaments, one shorter than the other. Additionally, at the end of the long flagellum, there appear to be "terminal hairs" (I represented 4, as indicated in Figure 19D of Kugrens et al. (1987)), but I'm not sure if there are actually exactly 4. According to the authors, this flagellar morphology is called "Cryptomonad-type 4 flagella," and it is also observed in Cryptomonas platyuris, C. marssonii, C. olozini, and Chilomonas paramecium. One troubling point to mention is that in that article, this flagellar morphology does seem to correspond to C. curvata, and "Cryptomonas rostratiformis" is mentioned as another species. As you know, it is currently considered yet another synonym of C. curvata.

There is no micrograph of the organism's cross-section. No, the illustration of the "anterior view," or "top view" for better understanding (as if you were looking at the "head" of the cell from above), is not a cross-section as such. In it, I represent the vestibule (omitting the two flagella, I only show two white dots that would be the "bases" of both flagella). Below the vestibule would be the gullet surrounded by ejectisomes. Incidentally, in the main illustration in ventral view, I represent the gullet surrounded by a single apparent row of ejectisomes, but in reality, there would be more rows covering the entire gullet. This is how it is represented in the drawings in Javornický (2014) (Figures 1 to 9). You can also see the anterior ends of both chloroplasts, and part of the nucleus, as well as the contractile vacuole and the furrow.

                                           

Finally, in the last illustration, the one of the whole, unsectioned cell, I know I said it's inspired by what you'd see in SEM (the reference is Figure 9B from Clay (2015)), but there are some creative choices. The existence of two shades of gray isn't natural; I actually did that to distinguish the two halves of the cell, especially so you can see the arrangement of the vestibule. The flagella should appear equally gray, not with those blue tones. That was to distinguish them better.

You know what annoys me about writing this post? I don't know why Blogger has been acting up; it won't let me post the images correctly, and they keep shifting around. I thought letting it sit would do the trick, but it's still the same.

I think that's all I have to say in this post. Of course, you can use any of these images freely; you know they're hosted on Wikimedia Commons. The only requirement is that you credit the author, for example, "DOTkamina 2025". 

That's all.