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

Porcupines of the Pond

This amazing creature is a heliozoan (literally ‘sun animal’), which is an amoeba that surrounds itself with a formidable battery of needle-sharp spines, radiating out from its core like sunbeams. Heliozoans are between a tenth and a quarter of a millimetre in diameter and drift through the water, slowly spinning. Each spine has a thin film of cytoplasm that flows up to its tip and them back down into the core, and any small food particles that the tip of the spine contacts are carried downwards on this conveyor and engulfed into the food vacuoles of the organism. The size of the core varies – normally it’s quite compact but it can expand by forming a mass of vacuoles (second and third photos down) and if it’s seriously stressed, like the heliozoan in the bottom picture, it flattens its spines and crawls across surfaces like a normal amoeba. These specimens came from water squeezed from moss on the edge of a pond. I used a microscope equipped with differential interference contract (DIC) optics to show the internal structure and needle-like spines. DIC optics generate a three dimensional image of transparent objects, which are otherwise difficult to see with conventional microscope optics.

Bubbling stones

The pebbles in the pools left by the falling water level in the upper reaches of the River Wear were bubbling in the bright spring sunshine this morning. Scraping some of the thin film of slime from the stones onto a microscope slide revealed the cause – millions of minute, photosynthetic diatoms, producing oxygen bubbles. In amongst them I found several amoeba, like the one shown in the second-from-top photograph, grazing on these underwater meadows.