A herd of rotifers!

[Pat Thielen]

More rotifers from the half frozen birdbath. There is an unbelievably high number of these guys in there -- I had no idea their population could be so concentrated. Anyway, here are a few more photos I took yesterday of them. I've been having a lot of fun watching them and actually seeing some form cysts on the slide; they can do this rather quickly once they sense the water is drying.

As always, let me know what you think.

[billbillt]

Hi Pat,

That is quite a large group!... You got some nice photos.. Very clear and sharp.. Thanks for posting!..

BillT

[charlie g]

Sure is a nice herd from your bird bath, Pat. I love that last image for all the detailed anatomy evident. Today(Wed, 11/8/17) my fingerlakes garden bird bath was mostly frozen too.

Charlie guevara

[Crater Eddie]

Great herd! This type of rotifer was the first microscopic creature that I was able to identify using my first ever microscope (mostly plastic) I had as a kid, more years ago than I care to remember. I always enjoy seeing them again.
CE

[Pat Thielen]

Hey -- I've got a question concerning rotifer physiology. I noticed a couple of the rotifers in the "herd" photo have a round thingy of some sort in the second or third posterior segment. Does anyone know what that is?

Thanks!

[Pat Thielen]

Hey -- I've got a question concerning rotifer physiology. I noticed a couple of the rotifers in the "herd" photo have a round thingy of some sort in the second or third posterior segment. Does anyone know what that is?

Thanks!

Found out in a book I have -- I'm pretty sure those round thingies are the rotifers' excretory bladders. And I didn't realize this before but rotifers have huge stomachs. Makes sense -- All they do is eat. I wonder what their metabolism is like and why these small creatures have to eat so much. It really is quite fascinating.

[MichaelG.]

Hey -- I've got a question concerning rotifer physiology. I noticed a couple of the rotifers in the "herd" photo have a round thingy of some sort in the second or third posterior segment. Does anyone know what that is?

Thanks!

.
Pat,
What I know about rotifers could be writ large on a postage stamp, but I've recently bought a useful little book [No.38], published by the Freshwater Biological Association in 1978.
If I am understanding this correctly: You appear to have some Male specimens in your herd. These typically have one large testis.

MichaelG.
.
Edit: Just seen your own update ... so I may be wrong !!
.
Edit: https://www.fba.org.uk/scientific-publications-sps

[Pat Thielen]

Hey -- I've got a question concerning rotifer physiology. I noticed a couple of the rotifers in the "herd" photo have a round thingy of some sort in the second or third posterior segment. Does anyone know what that is?

Thanks!

.
Pat,
What I know about rotifers could be writ large on a postage stamp, but I've recently bought a useful little book [No.38], published by the Freshwater Biological Association in 1978.
If I am understanding this correctly: You appear to have some Male specimens in your herd. These typically have one large testis.

MichaelG.
.
Edit: Just seen your own update ... so I may be wrong !!
.
Edit: https://www.fba.org.uk/scientific-publications-sps

I could be very wrong as well. I didn't come across any gender specific anatomy in my book so you could be quite right. I'm hoping a rotifer expert here in the forum will set all straight.

[MichaelG.]

The more I learn, the more I realise how much more there is ...

http://www.rotifera.hausdernatur.at/Species/Index/84

I've linked to that particular page because the Observation images [click the image to view full-screen] include a good one of the Male [ANSP 948].

... fascinating creatures.

MichaelG.

[vasselle]

Bonjour
Très belle série images de Rotifères.
Cordialement seb

[JimT]

I wonder what their metabolism is like and why these small creatures have to eat so much.

Probably because what they eat is so small

Nice images.I think that might be the intestine.

JimTT

[actinophrys]

If I am understanding this correctly: You appear to have some Male specimens in your herd

These rotifers are bdelloids. They don't have any males at any point – a clever look at chromosome divergence confirmed there hasn't been the sort of shuffling associated with sexual reproduction since the Mesozoic. How they have gone so long without it, when apparently other animal lineages that are exclusively asexual are very recent (suggesting they do not last long term), has been a question of some interest. The answer seems to have to do with anhydrobiosis, possibly since it rids them of parasites, possibly since the DNA repair mechanism it involves provides an alternate way of introducing genetic diversity.

[MichaelG.]

If I am understanding this correctly: You appear to have some Male specimens in your herd

These rotifers are bdelloids. They don't have any males at any point – < etc. >

.
I defer to your wisdom ... and would do so unconditionally if I had not seen the claim in Richard Dawkins' book "The Ancestor's Tale":
[ long link now deleted ... please see edit ]
Sorry about the long link but it gets you direct to the astonishing footnote on page 425.

MichaelG.
.
Edit: Apologies ... I appear to have broken the page layout with that long link.
... I will try again:
https://books.google.co.uk/books?id=Tub ... &q&f=false

[actinophrys]

But then as it says a single report, never repeated, and now considered superseded by some very good genetic evidence otherwise. In any case you can see at least these are not some strange dwarf males; photos like the first nicely show the paired ovaries characteristic of (female) bdelloids on either side of the stomach.

Anyway, I had meant to add: various diagrams confirm the circle as the location of the cloaca for excretion. Per Gastrotricha and Gnathifera ed. Schmidt-Rhaesa, this is usually associated with a distinct urinary bladder in monogonont rotifers, but in bdelloids that is absent and the terminal portion of the intestine plays the role itself.

As for eating all the time, I think that's the cost of being a filter feeder, where not every particle swept in as you graze is going to be particularly nutritious or even digestible. There are carnivorous rotifers like Collotheca and Asplanchna that instead enjoy higher quality meals but only get them now and then, and you can see the same sort of difference among ciliates too.

[charlie g]

Hey -- I've got a question concerning rotifer physiology. I noticed a couple of the rotifers in the "herd" photo have a round thingy of some sort in the second or third posterior segment. Does anyone know what that is?

Thanks!

Found out in a book I have -- I'm pretty sure those round thingies are the rotifers' excretory bladders. And I didn't realize this before but rotifers have huge stomachs. Makes sense -- All they do is eat. I wonder what their metabolism is like and why these small creatures have to eat so much. It really is quite fascinating.[/quote

Above my attempt to quote comments in your excellent microscopy posting, Pat..again...thank you for these rotifer images and this thread.

My 2001 text by Jan A. Pechenik : "Biology of the Invertebrates" (very low cost purchased used online...go for it!), and my more costly 2000 text edited by James H. Thorp & Alan P. Covich : "Ecology and Classification of North American Freshwater Invertebrates" ( look for it online...it will come down a lot in cost...BTW..the less costly texts of this area use same excellent chapter authors/ same excellent illustrations/ contemporary references...'go figure'!)...both clearly depict in clear anatomy illustrations.....that your image-captured rotifer does often have a 'bladder' ...identical to the 'round thingee' you asked about..and which you by online image search sensed was a bladder.


I note the 2015 genetic study clearly and emphatically demonstrated only a sexual shuffeling of the bdeloid (sp?) rotifers genes could have produced the genetic gene mix of a studied population of rotifers...this study (2015) has not been refuted/superseded/ found lacking in the literature from 2015 until our now waning 2017.

I always enjoy forum posting..and you, Pat,may note I'm reluctant to 'shoot out other forum folk on ID's, etc. '...but I offer a strong bravo to your sense that your images depict a bladder (according to my cited texts)...and the elegant and sound 2015 genetic study of a rotifer population always thought to be asexual/ all females...well there has been sexual gene mixing...this excellent work has not been refuted in published work. It made finger lakes/NY public radio when it came to publication with the cheerful note that those rotifer guys have been about after all.

What to do with forum conversations other than to offer cheer and a microscopists understanding of our world..offering reasons for ones opine! great rotifer images. Pat..before that rotifer herd are totally encased in ice ( like my bird bath here in fingerlakes/NY)...try and with higher mag objectives look at your rotifer neighbors 'flame cells'...they flicker so soothingly.

Charlie guevara

[MichaelG.]

Revised version:

As I hope I made clear; [in common with most of mankind] I know very little about the rotifers.

However: If [as seems very likely] the object is not a testis, then it does surprise me that it is so clearly visible in just two of the individuals.

Is this just an optical anomaly? ... I would be interested to know what others think.

MichaelG.

[Pat Thielen]

Revised version:

As I hope I made clear; [in common with most of mankind] I know very little about the rotifers.

However: If [as seems very likely] the object is not a testis, then it does surprise me that it is so clearly visible in just two of the individuals.

Is this just an optical anomaly? ... I would be interested to know what others think.

MichaelG.

I was thinking about this and I may have figured it out (or not; my knowledge is scant at best, non-existent at worse). Anyway, what may be happening is if those round thingies are indeed bladders then perhaps some of them have emptied. Also, they may not be as evident depending on how the individual rotifer is positioned.

[MichaelG.]

I'm pretty sure that you are right, Pat
... see my note [Wednesday] on your other thread.
viewtopic.php?f=6&t=5450

It certainly got me thinking though !!

MichaelG.