Field of Science

Sunday Protist -- Oligotrich Ciliates: another morphological acid trip

Of course, no one noticed any delays in the posting of the Sunday Protist, because that never happened. Actually, I've been rather frazzled by this little fun activity that happens around this time of the year called 'finals', and thus had to desperately avoid any material I may find myself actually interested in, lest it hijacks my attention for too long. Also, I'll be mostly internetless starting tomorrow, and thus unable to blog. Coming back on 03 January. May or may not schedule a post, depending on time, but wish you all a very happy holiday and see you next year!

But before I take off, let's oogle at some ciliates. Don't have much time (last final tomorrow), so this post will be very superficial. Just sit back, relax and enjoy the Cornucopia of awesome strangeness that is ciliate morphology. Today's special features Oligotrichs, conspicuous by their tuft of cilia at one end.

Let's meet the prime representative, Strombidium:

Strombidium inclinatum; the weird frayed flat-looking things at the top are actually flagella linked together into polykinety, formerly known as a 'membranelle' for its membrane-like appearance in light microscopy. Those usually constitute the oral ciliature, which are involved in feeding. G is the girdle kinety, basically a single row of flagella wrapped around the cell. It has very few kinety (which, btw, consists of kinetIDs, or basal bodies. Try not getting them mixed up on a lab exam...) compared to something like Paramecium or Tetrahymena, which are covered in rows of kinety. (Modeo et al. 2003 JEM)

For a reminder of where ciliates are on the Big [sub]Tree of Life, they're alveolates here:

I was playing with tree software this weekend. And then, to cleanse myself of the shame, I downloaded a cellular pathway modeling program and played around with some networks. This is the scheme we go by at this blog, at the moment (see the list of organisms towards the bottom of the side bar -->) "Craptophyte" was shamelessly stolen from some real protistologists. Proper term is 'Hacrobia'.
[disclaimer]By the way, while alveolates+stramenopiles and amoebozoa+opisthokonts are pretty good together, the other branchings may or may not bear any resemblance to reality. Furthermore, the rooting of the tree is highly contested, but I'll go along with what TC-S says these days (what Tom says is quite subject to change though...), since it'll be harder for you to argue with me as you'd have to read his stuff yourselves. And most of you are too lazy to do that, so I'm safe. I am in no way liable for any damage or deaths that may result from the use of this tree. [/disclaimer]

Here's another sampler of Oligotrichs and their neighbouring Choreotrichs (which we should explore at a later date):

(Gao et al. 2009 Sys & Biodiv)
And how they relate to each other:

Oligotrich (and Choreotrich) phylogeny. We'll briefly look at Strombidium, Laboea and Pseudotontonia.(Gao et al. 2009 Sys & Biodiv)

I may have something oligotrich-like in this old sequence of images documenting a random ciliate exploding while I was taking an optical stack... the image quality is kinda crappy, so I could probably get away with calling it Strombidium or something. I don't even remember where this sample came from, may well have been marine, hence the explosion in water.

Let's wander about the Oligotrich tree some more.
The first glimpse of Laboea made me double-check it wasn't actually some sort of tiny snail:

These SEMs are so nice I'm having trouble cropping them... (Agatha et al. 2004 JEM)

It also a rather unusual-looking (for a ciliate) cell division pattern:

Dividing Laboea sp. (Agatha et al. 2004 JEM)

If you've ever wondered how to tell a dividing ciliate from a conjugating couple, it's pretty easy: Ciliates divide transversely along the anterior-posterior axis, ie like <=<= if < style="font-style: italic;">Trichonympha is almost the polar opposite -- they divide laterally and have sex like this: <=<=. The Kama sutra of protists must definitely be written someday! See the bottom of this post for more ciliate sex.

Which is why Laboea looks a little weird, although here it must simply have a different longitudinal axis from what it first appears as. As much as I love morphogenesis/cellular development, and as much as tomorrow's final is Developmental Biol, ciliate morpho won't help much with chick gastrulation, sadly enough. Although it would be fun to draw parallels between various processes of development on morphogenesis to derive some fundamental principles, which I'm pretty sure (though only as much as a scientist can be sure about anything...) should repeat both on the unicellular and multicellular levels. After all, there's only so many ways to build a shape. So we'll have to pass on the cell division/morphogenesis stuff for now *sob*

Pseudotontonia. Ok, this thing is weird:

T - tentacles, TC - tail cilia. B shows a representation of the whole cell, which appears to have a very long 'tail' in addition to its tentacles. (Skovgaard & Legrand 2005 J Mar Biol Ass UK; free access)

To confirm that it really exists, there are pictures: (an SEM would be wonderful but this seems to be all we've got)

Pseudotontonia. Tail unfortunately not visible, although another image in the paper does show its beginnings. Fig F shows stained macronuclei. The thing is full of nuclear material. Ciliates have surreal genomes to match their similarly sophisticated cell structure. (Skovgaard & Legrand 2005 J Mar Biol Ass UK; free access)

Remember how Laboea has this weird division pattern, not very ciliate-like? To show how nothing makes sense except in light of evolution:

Proposed model of Oligotrich ciliary pattern evolution: The ancestor had multiple longitudinal rows of kinetids (basal bodies), which were subsequently reduced to two rows wrapping around the cell's main body. GK(red) - girdle kinety, VK(blue) - ventral kinety. c) Ventral kinety goes longitudinal. d) The anterior end of the girdle kinety went down to join its other end at the posterior (but not attach). e) The posterior end of the girdle kinety curved up along the ventral kinety. f) Posterior end of GK migrates upwards to form a circular girdle kinety at the anterior. g) Girdle kinety spirals down (eg. Laboea), ventral kinety disappears (Agatha 2004 Zool)

This helps make a bit of sense from the weird Laboea division -- the cells posterior (at least in terms of division) seems to be located elsewhere, messed up by the weird spiraling of the girdle kinety. The true posterior should be wherever the new cell starts to form. morphology fetish... mmmm, ciliates! *drools* This is a really sexy paper on ciliary pattern evolution in Oligotrichs. Hmm, passing tomorrow's final, or really sexy paper. Shit. This is awful. I can''t look...stop me!

Actually, I'm gonna wrap it up there.

So, to summarise, (I need an excuse to put in this nice diagram):

Summary of Oligotrichs. Phylogeny based on morphological characters (indicated by numbers; explained in the paper). (Agatha 2004 Acta Protozool.; free access)

(I'm confused by the discrepencies between this tree, the Gao et al. 2009 tree at the beginning, and a few other Oligotrich/Spirotrich trees I've seen tonight, but with a final looming ahead in a few hours...I'll be a horrible blogger and pretend to ignore it for now! So here I present two sides of the argument. I hope the creotards creationists are happy.)

Ok, one last glimpse:

The arrow in C points to the organelle where the oral ciliature develops. Wonder if it's similar to the determinative region of oxytrichs... (eg. Grimes 1982) (Agatha 2004 Zool)

Wow. Ciliates definitely kick some dino ass. Take that, you-know-who-you-are! =P

Apologies to those who feel I may not have done justice to the works in this post; don't have time... also, warning: there will be no Sunday Protist next week. But I'll make up for it next year! =D

Happy holidays! Hiatus

Agatha S (2004). A cladistic approach for the classification of oligotrichid ciliates (Ciliophora: Spirotricha) Acta Protozoologica , 43 (3), 201-217

AGATHA, S. (2004). Evolution of ciliary patterns in the Oligotrichida (Ciliophora, Spirotricha) and its taxonomic implications Zoology, 107 (2), 153-168 DOI: 10.1016/j.zool.2004.02.003

AGATHA, S., STRUDER-KYPKE, M., & BERAN, A. (2004). Morphologic and Genetic Variability in the Marine Planktonic Ciliate Laboea strobila Lohmann, 1908 (Ciliophora, Oligotrichia), with Notes on its Ontogenesis The Journal of Eukaryotic Microbiology, 51 (3), 267-281 DOI: 10.1111/j.1550-7408.2004.tb00567.x

Gao, S., Gong, J., Lynn, D., Lin, X., & Song, W. (2009). An updated phylogeny of oligotrich and choreotrich ciliates (Protozoa, Ciliophora, Spirotrichea) with representative taxa collected from Chinese coastal waters Systematics and Biodiversity, 7 (02) DOI: 10.1017/S1477200009002989

MODEO, L., PETRONI, G., ROSATI, G., & MONTAGNES, D. (2003). A Multidisciplinary Approach to Describe Protists: Redescriptions of Novistrombidium testaceum Anigstein 1914 and Strombidium inclinatum Montagnes, Taylor, and Lynn 1990 (Ciliophora, Oligotrichia) The Journal of Eukaryotic Microbiology, 50 (3), 175-189 DOI: 10.1111/j.1550-7408.2003.tb00114.x

Skovgaard, A., & Legrand, C. (2005). Observation of live specimens of Pseudotontonia cornuta (Ciliophora: Oligotrichida) reveals new distinctive characters Journal of the Marine Biological Association of the United Kingdom, 85 (4), 783-786 DOI: 10.1017/S0025315405011707

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