Life in 10 Drops of Water: Assorted Protists and rotifers

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

.... and finally another heliozoan, that appears to be ingesting something

Teeming Millions - Paramecium Population Explosion

Well, teeming thousands anyway. These little organisms are Paramecium, single-cells protists that swim with incredible speed using ciliary hairs on their surface, that beat in rhythm. Here they're magnified one hundred times. This single drop of  water on a microscope slide probably contained about five hundred...

... and this little pool of water, trapped in a cavity formed by the coalesced roots of a beech tree, must have contained millions, feeding in bacteria and other microscopic organisms that were in turn feeding on the rotting leaves trapped in the water. The pool is fed by rivulets of water that trickle down the trunk when it rains. Temporary pools of water trapped in plants like this are known as phytotelmata. The best-known examples are the pools of water trapped by the leaves of bromeliads (urn plants) that grow as epiphytes in the rainforest tree canopy. They host all sorts of exotic animals - tree frogs, land crabs, dragonflies - but this beech tree-root equivalent hosted nothing larger than rat-tailed maggots - the larval stages of drone flies. But while the species diversity in the beech-tree pool might have been low, the sheer abundance of the Paramecium was staggering. 

Here they are magnified two hundred times. The circles that you can see in some of them are contractile vacuoles, that constantly expell water from the cell cytoplasm.

  

At 400 times magnification you can see the fine cilia (top right) that are arranged in rows over the surface of the cell - you can just make out their dark parallel lines and you can also see algae that the Paramecium has ingested, inside the cell.

Static images don't really do justice to the helter-skelter movement of these little protists, but the video clip below gives some impression of what is going on in those little temporary pools of water trapped by the tree roots.

 

Lifting the edge of the blanket

I spent some time yesterday fishing the blanket weed out of my smallest pond, and took the opportunity to take a look at the microscopic organisms that live in it. There were vast numbers of ciliate protozoans, about a twentieth of a millimetres long, whizzing around at a tremendous speed. They are propelled by fringes of microscopic hairs that beat in rhythm and they can change direction instantly, so they can be tricky to photograph. The ciliate in the picture here might be a species of Oxytricha, but I’m not totally sure about that. The green objects inside it are algae that it has ingested. The two videos show a large rotifer that was attached to the blanket weed, with its ‘wheel organs’ (rings of rhythmically beating cilia) creating a vortex that sucks food into its constantly chewing jaws. These animals always remind me of twin-head electric razors. Blanket weed can be a pain in ponds, but it supports a vast array of minute organisms that are the base of a food chain for larger animals.