Genus/Species ID?

[modified lung]

I have two species of daphnids on my hands I think. I've been trying to ID them with this web site: 

http://cfb.unh.edu/cfbkey/html/choices/cladocera/40/40.html

...but I'm not great at these things and looking through a microscope for too long gives me a migraine.

Species #1 I'm reasonably sure is Daphnia magna but some confirmation would give more confidence 

 

Species #2 is a little over half the maximum size of #1 and behaves very differently. They are much smoother swimmers and cling to surfaces instead of hanging in the water column. They also have a much shorter nose, a little mouth-part thing, and shorter set of main swimming antennae.

They may originally come from the delta in northern CA because I've found them in my outdoor system which has some Elodea collected from the delta.

 

Dance party

Edited July 13, 2022 by modified lung

[Biotope Biologist]

Species #1 is definitely Daphnia magna I can make out the head shield in image 2 top one. 
 

Species #2 I have Simocephalus vetulus The teeth were kind of hard to see but I am pretty sure it’s arrow shaped. This species is still in the daphnia family.
 

I too used the guide you linked, but I can verify with my marine inverts and molluscs of the pacific key when I get home. Since most these species can occur in brackish I should have it in my book and that will also help narrow down the range. My preliminary searches showed this species being cosmopolitan though.

 

I’d be interested to see what others come up with. @OnlyGenusCaps maybe can confirm or refute our identifications.

[OnlyGenusCaps]

First off what are you doing up at this hour @Biotope Biologist?!

Secondly, it has been blissfully long since I have had to identify tiny little freshwater crustaceans to species.  Now, do know that I've not pulled out my old text to key them because that's bridge too far.  😜   But, quickly I concur with #1.  And for #2 I get some species of Simocephalus (in the dance party I thought I got a glimpse of the type of post abdominal claw), but I'm not going to species.  No, sir.  Not doing it.  Certainly not before my second cup of tea.  ☕

[Biotope Biologist]

On 2/16/2022 at 6:02 AM, OnlyGenusCaps said:

First off what are you doing up at this hour @Biotope Biologist?!

Secondly, it has been blissfully long since I have had to identify tiny little freshwater crustaceans to species.  Now, do know that I've not pulled out my old text to key them because that's bridge too far.  😜   But, quickly I concur with #1.  And for #2 I get some species of Simocephalus (in the dance party I thought I got a glimpse of the type of post abdominal claw), but I'm not going to species.  No, sir.  Not doing it.  Certainly not before my second cup of tea.  ☕

I was on the eastern seaboard for a week haha I certainly don’t want to give the impression I’m surfing the forums at 4:00 am. 😋

[modified lung]

@Biotope Biologist @OnlyGenusCaps I much appreciate it. Looking into Simocephalus, this definitely looks accurate. If they aren't daphnia, then knowing their genus is enough.

I got one more for you though. I found another population of magna, but these have some other organisms clinging to them, so many that they look fuzzy to the names eye. I can't find any daphnia parasite that looks like this.

They kind of look like rotifers but it seems odd rotifers would be living on daphnia. Pipetting the daphnia onto the plate knocked most of the organisms off and it looks like they can free swim as well as cling to surfaces with their foot.

And I'll only accept an answer at 4:00am.

[Odd Duck]

Waiting on pins and needles for the answer, now.  😆

Looks like some kind of rotifer to me but I’m certainly not an expert.

[Biotope Biologist]

I think it’s a rotifer, but I think they are different species of the Brachionus genus. 
 

The one that has me absolutely stumped to no end and frantically flipping pages in my book is the one on the head of the daphnia in the top image. If I didn’t know any better it looks like a juvenile tunicate. But tunicates don’t occur in freshwater and are rare in brackish…

[modified lung]

@Biotope Biologist You're awesome. They all looked the same to me under the microscope but now I'm wondering if I just wasn't looking close enough.  I'll have to grab some more and look again. They were found in an old tank in a field filled with rain water and some cyanobacteria.

[modified lung]

@Biotope Biologist @OnlyGenusCaps @Odd Duck 

I took some more pics if you're all interested.

Clinging to a daphnia:

Higher magnification:

Dance party:

Edited February 17, 2022 by modified lung

[Torrey]

So, two very strong reactions:

1. I am really missing my old microscope.

2. I really wish I could convince my BiL to join the Forum, because I could sip tea and read the discussions about identification all of you could have. 

I am the biologist y'all are, *and* I am really homesick for the science conversations. 

I recognize the big ones as daphnia. Extent of my knowledge. 

Thank you for posting pictures @modified lung, and allowing me to follow along.

Are any of you interested in identifying some pseudopods?

[modified lung]

@Torrey I know what you mean. I miss working for universities sometimes with all their fancy, new equipment. Now I'm in the private industry using decades old equipment that has rarely if ever been maintained (the second daphnia photo in the original post was taken with an LED flashlight under the microscope because the illuminator wouldn't turn on).

I'm terrible at IDing.

Edited February 18, 2022 by modified lung

[Torrey]

ORD, and thank you!

[OnlyGenusCaps]

On 2/17/2022 at 4:46 PM, modified lung said:

Dance party:

I like the dancing rotifers!

[modified lung]

I might have just found the answer. They are the rotifer Brachionus rubens. Apparently it's not uncommon for them to attach to daphnia and steal their food source.

 

Scroll down to "Rotifera" in link:

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/ceriodaphnia

 

[Biotope Biologist]

On 2/19/2022 at 1:30 PM, modified lung said:

I might have just found the answer. They are the rotifer Brachionus rubens. Apparently it's not uncommon for them to attach to daphnia and steal their food source.

 

Scroll down to "Rotifera" in link:

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/ceriodaphnia

 

And they kinda look like juvenile tunicates! I was worried I was starting to lose my touch and maybe going a bit mad like all the senior scientists keep saying will happen one day. I’m glad I have my sanity at least for now 😋

[modified lung]

I thought I'd share this one which has been stumping me for months. Normally they looks like this:

...but when under stress or maybe when exposed to the microscope light they darken their carapace and look like this:

For a while I thought they were two different animals until I saw one darken in front of me. Sometimes they turn maybe 75% black. I think the change comes from some kind of movement of the carapace because they can't seem to do it when under a cover slip.

Best I can tell they are in the Chydoridae family. But I can't find any reference to a color changing member of that family. And every other member seems to have a rounder body or a larger head.

The closest thing I've found is this: https://www.researchgate.net/figure/a-and-b-General-view-of-Dunhenvedia-odontoplax-c-carapace-posterior-part-d-labrum-and_fig1_5574413

But as far as I can tell that's the only reference to Dunhenvedia (a genus in the sub-family Aloninae within the family Chydoridae) that exists.

WHAT ARE YOU?!?!?!