Alexis Chaine <[log in to unmask]> wrote:
I was hoping that someone out there can give me a bit of insight into
Tetrahymena thermophila in its natural environment since very few studies
I have two questions:
1) How often do you take samples and don't get any T. thermophila? Another
way to think of this is how ubiquitous is it in a broad variety of ponds,
Two scenarios. My experience is that if ponds have thermophila in them, the % positive samples is seasonal. I don't have the exact numbers in front of me (can get them for you if you want), but early spring/late fall, 90-95% of samples are negative. I've never found thermophila if water temperature is <13C. In July/August, 70-90% of samples are positive, and often with 2 mating types (or 2 cells with same mating type but different molecular markers). If ponds are negative, they seem to be consistently so, but more sampling is needed on this point. Last year I sampled some ponds (for the first time, 3-4 samples, two occasions) during summer, found no thermophila, but did found themophila in nearby ponds,
This past summer I collected at ~55 ponds in New England, finding thermophila (mature ones) in, I think, 5 ponds. Much work remains to be done.
2) Is its usual habitat often connected to other ponds by streams - and if
so, do you think they ever disperse through streams or is it just transfer
by other means (duck's feet, etc...)?
The ANF ponds I usually sample, with a few exceptions, are NOT connected by streams and some are 25 miles apart. I don't know how the thermophilas got there, and I speculate that it could be from some fish stocking, a fisherman's bucket, etc. It appears (unpublished) that ANF thermophilas are most closely related to the original thermophilas from WoodsHole MA. Their COX sequences differ from other New England samples. Recent isolates haven't yet been sequenced.
Nanney found thermophila in a temporary pond, a roadside ditch, a strange place. Decades later I searched the whole county where he took the sample and found no tetrahymenas. As to natural dispersal methods, waterfowl, snails, wet beavers, dragonflies, swallows, windstorms, all come to mind. Overwintering is another problem. I've never sampled in the winter.
3) If you go collect in the wild, how many different species do you get in a
small sample (maybe by volume....very roughly)?
We're just recently getting data on this point. Usual sample volume is ~140ml.
In thermophila ponds, I'm guessing 6-10 thermophilas to 1 other species. In ANF ponds we have evidence of at least 4 other Tetrahymena species. There are many amics.
4) In a single sample, how many mating types do you find among the T.
I think the average is about 1.6 thermophila mating types in thermophila positive samples. In samples of 140 ml the range is 0 thermophila to all seven mating types. This is complicated by the fact that ~20% of thermophilas are immature, failing the initial mating type test.
Hope this helps a bit. Don't be afraid to call or email back. This is fun stuff.
Thanks again for all your excellent past and future help!
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