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Quite a crowd! It's Spirostomum teres.

Naegleria is a heterolobosean amoeboid, a group in which pseudopods are formed eruptively (kind of like bubbles erupting from the leading edge of the cell). We don't see that, here: it is moving like an amoebozoan. With those short, digitate pseudopods, I think this is probably a species of Mastiga...

A real beauty!

The first one appears to be the fragment of a hypotrich (unless you find a whole population of them, in which case we need to look more closely :D). It is moving in a way that looks unnatural, to me, so I think it is a damaged organism and not a recent divider. The second one appears to be a heterot...

Yes, A. procerus ! It resembles Litonotus cygnus , but has multiple contractile vacuoles and a little fan of extrusomes at the tip of the proboscis. The two-part macronucleus is a very common feature in members of the order Pleurostomatida, so it's not too useful as a character of the genus or speci...

It's oddly shapeless, for a flatworm. I don't know much about them, unfortunately. It crossed my mind that it might be a freshwater acoel, but I really have no idea.

I can see why macnmotion is thinking of Trachelius , but the membranous structure that surrounds this critter is too thick to be the cortex of a tracheliid, or any ciliate...I'm pretty sure it's the ectoderm of some kind of flatworm, or perhaps a freshwater acoel. It encloses structures that appear ...

Yes, good point....in addition to the caudal cilium there are several long posterior somatic cilia. That's not unusual for a scuticociliate, but it is an important feature. I see that Sathrophilus chlorophaga (number 33 in Kahl's plate, above) also has elongated posterior cilia.

That's a really cute creature! It appears to be a scuticociliate, but with a somewhat Tetrahymena -like shape. It has a long caudal cilium, and a rather bumpy, ornamented pellicle. I'm thinking of Sathrophilus (= Saprophilus ). The genus has not had much attention since Kahl, who described and illus...

Yes, this is Spirostomum teres. Beautiful footage, too!

Thanks for the link to that fascinating paper, Josh! I don't know nearly enough to have opinions about the arguments Devos makes, but I take your point: the jury is still out on Neomura.

my apologies to steve for this hijack of his wonderful thread on epibionts observed on late winter mayfly nymphs Yes, sorry for the detour! We've wandered a long way from Carchesium . Since you mention a wonderful professor: Dr. Thomas Cavalier-Smith....well I'm cheered we share this professors sig...

> I always liked that word protozoa! I do, too! As an informal term for non-photosynthetic unicellular organisms, it hits the spot. "Protist" is fine, too, as a catch-all term for "eukaryotic critters that are not animals, plants, or fungi." However, things get weird if we retain these old terms as ...

( peritrichs a sloppy often used term for this wonderful group of ciliates Hi Charlie! You've raised some interesting points. :) First, the term "peritrich" isn't sloppy at all! Peritrichia is a well-defined and strongly supported natural group (clade). In 2017, Eleni Gentekaki & her collaborators ...

Yes, it is in the family Vaginicolidae, and is probably in genus Vaginicola. We don't see a stalk or valve on the lorica, or an operculum (a lid-like attachment) on the cell, but magnification is low so any of these structures could be hidden from view.

Yes, it's Carchesium (colonial, with spirally-contractile stalks).

Fascinating!

Yes, these are a species of histophagous (tissue-eating) ciliates in the genus Tetrahymena, devouring the contents of a dead rotifer.

Very nice! Paranassula is a marine genus, I believe (and not a nassulid, oddly! It is currently considered a peniculid, like Paramecium ). Nassula aurea is now in the genus Obertrumia . That genus is differentiated from other nassulids by a small difference in a structure called the "hypostomial fra...

It's definitely damaged. It looks like a fragment of a heterotrich (Spirostomomum, Stentor, etc.)

A wonderful collection of critters! This was a brackish or marine sample, presumably? These are mostly ciliates found in salt water. The first is a karyorelictean ciliate with a slightly beaklike (rostral) anterior. At first I thought it was a species of Geleia , but I now think it is actually Kentr...

We're seeing this guy from the side, and the distribution of ventral cirri is not visible. So, the best we can do is...subclass Hypotrichia. Anything else would be a guess (Uroleptopsis is a saltwater ciliate, btw...if you're sampling marine waters it's important to mention that).

Great catch! The peritrich is Epistylis, and yes, the predator is a species of Amphileptus.

It is a vampyrellid amoeboid: https://arcella.nl/vampyrellida/

This appears to be a sick or damaged cell, moving in an abnormal way. It's not unusual to find pieces of damaged ciliates still swimming around, and even trying to feed. Your best hope of identifying it is to look at other (healthy) organisms in the same water.

The still image shows helpful details, such as the long caudal cilium, and the cilia that surround the cell. This is in the same order as Pleuronema (Pleuronematida) but is a species of Cyclidium.

I'll dive more deeply into my Kahl's, Kudo's and Foissner's texts to study the genuses you mentioned. Sterkiella was created in 1991, and Tetmemena in 1999, so you won't find them in older texts, though you will find many species currently in different oxytrichid genera. At the species level, Kahl ...

OK...we have a big oxytrichid, with a relatively large AZM; left and right marginal cirri in single rows; distinct caudal cirri, closely spaced. Undulating membranes are not very clear, but buccal structures are obviously not like Steinia or Cyrtohymena . The cell shape is oddly variable, which make...

Beautiful images!

The first one is Strobilidium caudatum ("Strombilidium" is a fairly common misspelling, because of the similar-looking genus Strombidium).

The Trachelomonas-eater is indeed a hypotrich...or part of one, at least (it might be a damaged cell, or half of a recent divider)

OK, I see what you're referring to, now. :D It looks to me like you ruptured the ciliate's plasma membrane when you compressed the poor thing, and it lost some cytoplasm. Some ciliates can recover from damage of that kind, provided nuclear structures are intact. I don't see anything here that looks ...