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

Another Rotifer....

I've posted pictures of rotifers before (here) but they are such amazing animals that there's always room for another - especially this one, which looks like a monster from a sci-fi horror movie. I found it at the edge of a pond today and it is - I think - a species of Euchlanis, which belongs to a group called loricate rotifers. A lorica is a hard outer shell (the word lorica is Latin for 'body armour') that provides protection and maybe has hydrodynamic properties that aid swimming. The protective function is evident in this photograph (above), where the animal's head is withdrawn into its shield-shaped lorica, which has claw-like points guarding either side of the opening. The animal is about a fifth of a millimetre long.

It may be that the shield-shaped lorica also functions like a wing, generating lift as the animal swims through the water, powered by a tuft of fast-beating cilia at the head end-  which you can see beating in the short video below. When at rest the animal can anchor itself with its tail spines, which open and close like a pair of scissors.

These images were taken with differential interference contrast optics, which generate an apparent three-dimensional image of microscopic objects.

You can find out more about rotifers here.

Klingon Warship

I found this little rotifer called Keratella, looking like an armour-plated Klingon warship, or maybe a medieval chain-mail glove, in a moorland pool about 500 metres above sea level in Weardale. Under the microscope it looks like a swimming claw, propelled by those whiskery looking hairs that you can see between the armoured ‘fingers’, which also serve to produce a water current that sweeps minute food particles into its jaws. The red spot is a light-sensitive eye spot. Most amazing of all, that egg-shaped object being towed around behind one of them is an egg – but not just any old egg. These animals reproduce by cloning themselves and never reproduce sexually, so the individual inside the egg is an exact genetic copy of the adult animal it’s attached to. When I peered down the microscope, I could see this animal’s alter-ego squirming inside the egg, ready to hatch. Keratella is about a quarter of a millimetre long.

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.

Rotifer

This is a rotifer - a tiny aquatic animal about one tenth of a millmetre long. Twenty, placed end to end, would stretch across the head of a dressmaker's pin. Rotifers feed by using two circles of rhythmically beating cilia ('wheel organs') on their head, which create a vortex that sweeps food particles into their digestive tract, into the path of constantly grinding jaws called the mastax, which you can see below the wheel organs. The animal attaches itself with a tail and, in some species, when it lets go of its anchorage the wheel organs can become propellers. Rotifers are every where where there is water - in puddles, in wet mosses and even in a vase of flowers that has been standing on the windowsill for a few days - which is where this one came from.