This is the fourth in the series of images of some of the organisms found in just a few drops of water collected from a pond in a disused quarry on the edge of the moors in Weardale.
An amoeba. I could spend a long time watching these - it's rather relaxing watching an organism whose motto for life must be 'go with the flow'
It seems to have ingested a wide varieties of objects.
This is one of the free-swimming ploimate rotifers, with tails that look like scissors - possibly Monommata caudata...?
Vorticella - a ciliate protist on a stalk, that contracts like a spring when disturbed. The green object is a cyanobacterium - possibly Gloeocapsa.
A ciliate protist that creeps along using strange 'whiskers' - and also swims very actively using smaller cilia. You can see a contractile vacuole quite nicely here. I think this, and the three below, might all be Oxytricha.
All three of the above ciliate protists look rather well fed - full of undigested algae.
This beautiful object is the flask-shaped shell of the testate rhizopod Cyphoderia ampulla. The amoeba that lived inside has long-since died.
I thought this might be the shell of a testate rhizopod, but Natalia has kindly identified it as a tintinnid ..........
... at higher magnification you can see that it's constructed of tiny translucent particles....
... that are especially fine and fit together beautifully around the orifice