What is this thing?

[Josep]

I found this in a sample of one of my fresshwater aquarium... does anybody know what is it?
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[BramHuntingNematodes]

probably a water mite or if i see festoons in the second picture maybe a lost hard bodied tick but thats more about me having ticks on the mind. you need to catch it and look at more closely!

[Josep]

I have no idea how to catch it. It is really small, I can't see it with my eyes...the photo was taken with 250x. I was trying to identify it before ask here, so don't have the sample anymore. I will extract some algae more from de aquarium, maybe I can found more specimen like this to look more closely. Thanks for your answer

[Greg Howald]

It does very much look like a tick.
Greg

[Josep]

It does very much look like a tick.
Greg

It seems to be, but is too small I think... and it was underwater all the time... I taked an small part of java moss at around 25cms underwater, to see what could I see living there when I found it.

[BramHuntingNematodes]

Mmm yes. Very small for a tick, but there are plenty of water mites that would fit the picture. There are some keys around I think if you can get a closer look. There is hardly ever just one mite after all.

[dtsh]

probably a water mite or if i see festoons in the second picture maybe a lost hard bodied tick but thats more about me having ticks on the mind. you need to catch it and look at more closely!

Looks like festoons to me and as I understand it, ticks can live an amazingly long time underwater. Some aspects of it don't quite match what I expect of a tick though, not that I'm all that knowledgeable about ticks.

Jopsep,
Any chance you can get some images, especially of the ventral surface, the back of it to see the "festoons" (if they are indeed festoons), and the head?

[Josep]

probably a water mite or if i see festoons in the second picture maybe a lost hard bodied tick but thats more about me having ticks on the mind. you need to catch it and look at more closely!

Looks like festoons to me and as I understand it, ticks can live an amazingly long time underwater. Some aspects of it don't quite match what I expect of a tick though, not that I'm all that knowledgeable about ticks.

Jopsep,
Any chance you can get some images, especially of the ventral surface, the back of it to see the "festoons" (if they are indeed festoons), and the head?

Maybe. I will collect some more sample from the aquarium and I will take a look.

[Michael Müller]

Its not a tick, but a aquatic oribatid mite that live in water. They are not freely swimming and so soft as true water mites but have a very hard shell. For an identification to species-level it is necessary to have a closer look to it.

[Josep]

Last night I found this one in another sample of the same aquarium. I am not sure it is the same species, but should be. Maybe this is an adult, or different sex, or isn't really the same... Sorry for the pictures quality, the depth of field is very short... I need to find an easy way to make a focus stacking with the mocroscope.
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A closer view of the back.
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The head and part of the back.
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Closer views of the head
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[Greg Howald]

Your much clearer image would indicate that this is not a tick. It has far more additional hardware attached to it than that of any typical tick.
Greg

[dtsh]

I agree with Mr Howald, given more context and something for scale it's likely a mite of some sort.