Dwarf forms of Stentor: How do they originate?

[NachoBen]

I often find dwarf forms of the genus Stentor in my samples. Although they do not have the size or shape typical of each species, they are easy to recognize thanks to the AZM and the paroral membrane, as well as the color (the color in Stentor coeruleus and Stentor igneus is typical). You can see an example of a dwarf form of Stentor coeruleus in this video:



The question is: How do these forms originate? Are they mutants? Do they occur in an unequal bipartition? Stentor rarely go into cysts so it is hard to think of these forms as swarmers.

Thank you for shedding any light on this issue!

[Free2Fish]

Nice imaging! That little guy/gal is acting like a runway model, showing off his/her best sides. Sorry, no idea how they form.

Harry

[Bruce Taylor]

Stentors have a remarkable ability to survive and regenerate after suffering damage. As long as a piece of the macronucleus is preserved, even a small portion of a damaged cell can recover from trauma. During regeneration, the cell is apt to look pretty strange. Also, while Stentors do not have unequal division (e.g. budding), post-dividers of normal division will, of course, be half the size of the mother cell.

One more thing...don't assume that every blue-green heterotrich is S. coeruleus! Be on the lookout for a smaller blue-green Stentor with a single macronuclear bead, S. multiformis. Another critter to look out for is Condylostomides coeruleus, a soil ciliate with a very similar colour which could sometimes be mistaken for a deformed Stentor.

[NachoBen]

Thank you once more for the info, Bruce.

Although all my samples with Stentor are fresh water ones (large puddles, ponds, river backwaters, reservoirs) I will be on the lookout for a possible encounter with Condylostomides.

Concerning Stentor multiformis, I have never found it. Although I have sometimes observed its beautiful "Greek brother" Stentor polymorphus!