Is this Paramecium multimicronucleatum?

[NachoBen]

Hello everybody!

I have to apologize once again for uploading a dark field video, I know that it is difficult to determine the characteristics of protozoa with this method. The critter in this video is a little hard to identify for me (although by now I am supposed to know several species of paramecia!).



I think this could be Paramecium multimicronucleatum. Can someone confirm or rule it out please?

Thanks a lot everybody.

[Bruce Taylor]

Identifying Paramecium species in the light microscope is actually quite difficult, and often impossible. At best, it requires a close inspection of features that are difficult to see, such as micronuclei and the pores of the contractile vacuole. Accurate measurements are also important, and multiple specimens may be needed to show the size range within a given population. In 2010 Sergei Fokin tried to provide a morphology-based key to the genus: https://www.researchgate.net/publicatio ... rimination . With Fokin's key, identification of P. multimicronucleatum requires a view of both the number and type of the micronuclei (yes, you not only have to count the micronuclei, you have to see them well enough to determine their type!).

But it gets worse! Since that paper was published additional morphospecies have been discovered. And worst of all...a lot of cryptic diversity has been revealed within existing species! P. multimicronucleatum, for instance, has two new lookalike species, P. lynni and P. fokini. See: https://www.mdpi.com/2076-2607/10/5/974 So, even if you manage to see the micronuclei in your possible-multimicronucleatum (which is difficult to do without special stains) you cannot rule out those newcomers.

In addition to the cryptic diversity revealed by molecular phylogenetics, we have the ongoing proliferation of sibling biological species within several traditional morphospecies. I think there are now sixteen named siblings in the P. aurelia complex. It's likely that most, if not all, of the known morphospecies are actually complexes of this type, though only a few have named mating types.

Because of all this, I rarely try to identify Paramecium to species, anymore. Even good old P. bursaria requires a bit of alertness, since the rediscovery of another green species, P. chlorelligerum.

[NachoBen]

Wow, Bruce! Let me thank you with all my heart for this new Protozoology lesson (including the valuable references).

By the way, the first link appears incomplete (it may be too long), it should be this: Paramecium genus: biodiversity, some morphological features and the key to the main morphospecies discrimination (https://shorturl.at/gmE37)

Everything you explain about Paramecia (I think they are one of the favorite species of microscopists) is very interesting, and you have clarified many things for me.

On the other hand, it is a bit sad to know that, as an amateur, little can be done to identify the critters we see every day. Nature is always ahead of us and, when we take a step, it is to discover how much we do not know (fortunately, because that is essential for the advancement of knowledge).

Also, you have thrown cold water on me about P. bursaria, one of my favorites. These days I am observing a spectacular and beautiful massive development of these organisms. I am very happy with my observations and the videos I have made of them. But what if they are P. chlorelligerum?

There is no choice but to continue learning, thank you very much again.

[Bruce Taylor]

Thanks for fixing that link!

On the other hand, it is a bit sad to know that, as an amateur, little can be done to identify the critters we see every day.

We can still identify them...just not necessarily to species. Even genus can be difficult in some groups. Since Vorticella was split in 1976, ruling out Pseudovorticella can often require silver stain (an inconvenient fact that most amateur microscopists prefer to ignore ). Distinguishing genera within the family Trachelophyllidae can require examination of their epicortical scales in the scanning electron microscope. And molecular phylogenetics has exposed flaws in other morphology-based classification schemes. At one time, you could distinguish members of the family Epistylididae from Opercularidae by their peristomial lips. However, molecular work has shown lipped epistylids (Epistylis galea, Campanella) nestled among Opercularia species, so that lip is no longer reliable as a character of the family!

Also, you have thrown cold water on me about P. bursaria, one of my favorites

Luckily, that one can still be identified in the light microscope (at least for now!). The morphological criteria are given here: https://pubmed.ncbi.nlm.nih.gov/22827482/

[charlie g]

Thanks for an interesting thread, 'nachoben'...and hear, hear thankyou, Bruce, for your postings here, and those PubMed links regarding P. bursaria, and the 'other paramecium with internal symbiotic algae'.

I agree with Bruce: 'it is enriching even to get to genus level grasp' of so many of our protists, and meiofauna neighbors.

I enjoy my P.buraria , and other symbiotic hosts of internal algae. Just yesterday I enjoyed a simple wet-mount slide ( first drops from a water sample from my mesocosm/ pond/stream outdoor setup). Hydra with

symbiotic green unicellular algae ( I am now squeemish to say Chlorellae genus of algae after Bruce provided links), and P.bursaria similar size/shaped symbiotic algae. A wonderful wetmount slide!

Thanks for this posting, nachoben and Bruce. charlie g

[einman]

I struggled trying to identify organisms to the species. I felt not doing so was just being lazy. However, over time and many papers ,I concluded that the ability and the time to determine the species went beyond my "hobby" and encroached on my other interests. So, I am now quite content to identify the genus and hazard a somewhat educated guess at the species, recognizing the odds were against me at getting it right based on the time and methods utilized!!!

Nevertheless, I enjoy doing so. As pointed out, the use of genetics for identification has demonstrated using physical characteristics alone simply narrows the choices.

[NachoBen]

Thanks Bruce, I've read the article you attached and as far as I understand, it looks like my critters are real Paramecium bursaria. That's a great relief!