Help ID Oxytricha saltans?

carlos.uruguay · Post by **carlos.uruguay** » Thu Mar 06, 2014 6:35 am

This saltwater ciliated measures about 75 um long (0.075mm). We found on the shores of the Atlantic Ocean at La Paloma - Uruguay.
It resembles Oxytricha saltans although we are not insurance.
Polarized oblique light.
Objective 40X
Link:
http://www.youtube.com/watch?v=3ZwYKAtfKrI
This link is one of few references that I found:
http://www.naturamediterraneo.com/forum ... _ID=198326
But it is not exactly equal to the video ciliated
Regards
carlos

Bruce Taylor · Post by **Bruce Taylor** » Thu Mar 06, 2014 6:00 pm

Very clear video, Carlos!

Short peristome, long transverse cirri, body 75 micrometres long, oxytrichid pattern of ventral cirri, saltwater habitat... I think Oxytricha saltans is a very plausible identification. I can't make out the nuclear structures very well (O. saltans would have a double macronucleus), and Berger describes a thorn-shaped feature on the buccal lip, which I can't detect, here. Did it have a jumpy, jerky way of moving?

For more info: W. S. Kent (writing about it under the genus Actinotricha) mentions the anterior and posterior "eye-like corpuscles," which we certainly see here. Kahl gives a paragraph to the species (under the sub-genus Actinotricha, on p. 604), and Helmut Berger gives a thorough historical review and description of it in his Monograph of the Oxytrichidae.

carlos.uruguay · Post by **carlos.uruguay** » Thu Mar 06, 2014 8:05 pm

Thank you very much Bruce
She was still a few seconds and then jumping to a near location to stay quiet again
Confused me the large cirrus indicates in this image, didn't see them described

Bruce Taylor · Post by **Bruce Taylor** » Thu Mar 06, 2014 8:51 pm

Yes, those ventral cirri are very well developed, which is perhaps inconsistent with Berger's description (he says all but the transverse cirri are "rather fine"). However, I think the focus in your still image exaggerates this a little bit. And other prominent features -- that tall crown of distal membranelles, the anterior and posterior "conspicuous shining globules" (Berger's phrase), the long and heavy transverse cirri -- fit the Oxytricha saltans morphospecies pretty well. Your specimen might belong to a local variant, or subspecies (or it might just be a distinctive individual).

Protos · Post by **Protos** » Fri Mar 07, 2014 5:44 am

Very nice Carlos !

It almost looks like DIC

carlos.uruguay · Post by **carlos.uruguay** » Sat Mar 08, 2014 7:29 am

Thank you Bruce, then I will set 'probably' Oxytricha saltans.
Thank you Protos for your kind comment, sometimes a beautiful effect is achieved with oblique polarized light and phase objectives with the condenser in position of bright field
Unfortunately I cannot acquire the necessary thing for DIC for the time being because it is very very costly
Regards
carlos

Bruce Taylor · Post by **Bruce Taylor** » Sat Mar 08, 2014 10:55 am

That seems reasonable, Carlos.

It's great to be scrupulous about identification, to avoid introducing badly-named pictures into the image pool (in the echo-chamber of Google Images, sloppy identifications reinforce one another). However, we need to remember that very, very little is actually known about these so-called species, so we should not make make taxonomical hygiene into a religious dogma.

In truth, the notion of species is already problematic. For one thing, these old "morphological species" (identified by physical traits visible in the light microscope) do not necessarily correspond to either biological or phylogenetic species. To take the most famous example, back in the 30s, the great ciliate researcher Tracy Sonneborn found that Paramecium aurelia was actually made up of at least 14 genetically isolated biological species (i.e. compatible mating groups). Each was given its own name (P. primaurelia, P. biaurelia, etc.) So, it became customary to refer to P. aurelia as a "species complex," and it was assumed that most, if not all, ciliate "species" were really loose groupings of that sort. (In populations within such "complexes," we might expect to find local variations, like the heavy ventral cirri on your O. saltans).

But recently, to confound things further, genetic analysis has shown that different strains of these "biological species" fail to fall into proper monophyletic groups, and do not meet the criteria for phylogenetic species! (Hall & Katz, 2011; Catania et al, 2009) The mating types are a phylogenetic hodgepodge. So, there is currently no species concept that can be used to sort out the members of the Paramecium aurelia complex.

And P. aurelia is one of only a few protists that have been studied in detail. Nearly nothing is known about O. saltans!

There are similar issues in other protist groups (for an interesting account of certain testate amoebae, see the brand new article "Cryptic Diversity within Morphospecies of Testate Amoebae," Oliverio et al, 2014).[/i]

carlos.uruguay · Post by **carlos.uruguay** » Sun Mar 09, 2014 7:38 am

Thank you Bruce. It is difficult to film videos without trying to put a 'name'