Oxytricha or Stylonychia?

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NachoBen
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Oxytricha or Stylonychia?

#1 Post by NachoBen » Wed Mar 15, 2023 6:59 pm

I know Hypotrychia is one if the most difficult ciliate group so I often have problems identifying these critters.

In this case I have found these large specimens with two nuclei and very noticeable cirri.

In this video you can see that they appear slightly compressed by the cover glass. The smallest organism's shape being the most common.


https://youtu.be/4rENvI1UeSI

I have narrowed my search to two common genera. My critters lack the three long caudal cirri so typical of Stylonychia but their overall shape seems to match. However, frontal and transversal cirri suggest Oxytricha.

What do you think? Help needed. Thank you!

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Re: Oxytricha or Stylonychia?

#2 Post by NachoBen » Thu Mar 16, 2023 9:15 am

In this new footage cirri are more easily seen.


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Re: Oxytricha or Stylonychia?

#3 Post by NachoBen » Thu Mar 16, 2023 9:48 am

And a new one. This is a fat guy: 350 µm in length.


Bruce Taylor
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Re: Oxytricha or Stylonychia?

#4 Post by Bruce Taylor » Thu Mar 16, 2023 3:13 pm

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 makes me think these specimens are being compressed under the coverslip. That is unfortunate, because it changes the natural appearance of the critter, and makes it more difficult to determine whether the cell is flexible (oxytrichine) or stiff (styonychine), but I think these guys fall in the latter group. Some specimens have a slightly pointed posterior, others are very round and wide in the posterior (likely because of compression). The anterior has a somewhat faceted appearance, a feature found in species of Tetmemena. I would lean toward that genus, thinking maybe of Tetmemena bifaria or T. vorax. It could also be a species of Sterkiella, or one of the historic species traditionally assigned to Stylonychia, but in need of redescription (some of these likely belong in other genera).

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Re: Oxytricha or Stylonychia?

#5 Post by NachoBen » Thu Mar 16, 2023 3:26 pm

A thousand thanks, Bruce!

I'll dive more deeply into my Kahl's, Kudo's and Foissner's texts to study the genuses you mentioned.

I already wrote about the compression because of the coverslip, I am deeply sorry for that. I am trying to get another sample with some more of these critters in order to make additional footages of (I hope) not compressed specimens.

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Re: Oxytricha or Stylonychia?

#6 Post by Bruce Taylor » Thu Mar 16, 2023 4:53 pm

NachoBen wrote:
Thu Mar 16, 2023 3:26 pm
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 remains very useful. Helmut Berger revised the Oxytrichidae in 1999 (https://link.springer.com/book/10.1007/ ... 011-4637-1), and his monograph is an important resource for the group, but even that is somewhat out of date, and needs to be combined with more recent work.
I already wrote about the compression because of the coverslip,
Oh sorry...I overlooked your comments!

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Re: Oxytricha or Stylonychia?

#7 Post by NachoBen » Thu Mar 16, 2023 5:15 pm

Giant masterworks from German scientists. Fortunately, you are so kind to struggle with so many references (many of them hard to find) and shed some light on us.

Be Tetmemena or Sterkiella, this organism has had a busy time reproducting in the last days. Perhaps a teratogenic sustance is accumulating in the pond since it is easy to observe strange uneven bipartitions like the one you can see in this video (only one from many observations):


https://youtu.be/QG-BjuXeWEI

Bruce Taylor wrote:
Thu Mar 16, 2023 4:53 pm
NachoBen wrote:
Thu Mar 16, 2023 3:26 pm
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 remains very useful. Helmut Berger revised the Oxytrichidae in 1999 (https://link.springer.com/book/10.1007/ ... 011-4637-1), and his monograph is an important resource for the group, but even that is somewhat out of date, and needs to be combined with more recent work.

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