'Mini-beasts' and microscopic plants in a garden pond

drawings by William Ells with additional notes by David Walker  

Garden ponds are becoming more and more popular and they can provide many fascinating subjects for the amateur microscopist. They are a 'world within a world' and contain a surprising variety of single-celled and multi-celled organisms.

 One of the best ways to learn about the structure of an organism is to draw it. The sketches below are of microscopic organisms that may be found in a pond, and have been drawn by Bill Ells, Maidstone, UK.

 Multi-cellular or uni-cellular?
There are twelve organisms shown in the accompanying diagrams, four are multi-cellular and the remainder uni-cellular. The name in italics below is the genus to which each organism belongs. The text in quotes are remarks by the illustrator, Bill Ells.

 One of the fascinations of studying pond-life is the incredible variety of shapes, sizes and behaviour of these microscopic organisms. Here are a few you might find.

Rotifers are muti-cellular organisms and have discrete organs such as a heart and eye.
A: Squatinella. This rotifer has a conspicuous transparent shield over the head, and the eyes have lenses.
B: Colurella. This is a sessile rotifer i.e. it attaches itself to an object by means of it's foot.

Colurella features in a Micscape article where a female's egg is attacked by protozoa. See The Good, the Bad and the Ugly .
C: Collotheca. "The cilia of these species do not wave about they are withdrawn into the body of the rotifer, taking food in. In the withdrawn position they look like shaving brushes."
D: Philodina. "The cilia of these species really look like wheels". This is P. roseola a species of rotifer often found in bird-baths. See The 'wheel-animal in a bird-bath' .

E: Coleps These are the armoured tanks of the protozoa world and also feature in the The Good, the Bad and the Ugly . Bill remarks "when I first had a microscope in 1976 my wife and I spent several hours watching these dividing, the 'barrel' comes apart in the middle but the two halves remain joined by two transparent hemispheres, one on each half, they eventually break apart and the hemisphere grows to complete the new Coleps".
J: Amoeba (Vexillifera?) This amoeba has spiny pseudopodia.

Algae (Microscopic plants)
The first two algae below are desmids which are a fascinating group.
Typically each cell is divided symmetrically into semicells which are mirror images of each other.
H: Closterium. "These were abundant in the sample, 41 cells being found in two drops of water, one seen dividing."
I: Cosmarium. "A variable species".
F: Scenedesmus. Two different species are shown.
G: Gonium. Consists of colonies of cells.
K: Gomphonema growing on the branched filamentous alga Cladophora. Gomphonema is a diatom, another fascinating group of algae which have silica cell walls, the two halves of which fit together like the old pill boxes. Resolving the fine details on the shells of many species is a popular challenge for amateur microscopists.

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Comments to Bill Ells welcomed.

 Further Reading
1) A Beginners Guide to the Collection, Isolation, Cultivation and Identification of Freshwater Protozoa by B J Finlay, A Rogerson and A J Cowling. Published by the Freshwater Biological Association, The Ferry House, Ambleside, UK, 1988. (78 pages) ISBN 1 871105 03 X.

 2) A Beginners Guide to Freshwater Algae by H Belcher and E Swale. Published by the Institute of Freshwater Ecology, Natural Environment Research Council, Cambridge 1978. (47 pages) ISBN 0 11 881393 5.

The Micscape editor's thank Bill Ells for contributing the drawings and additional commentary which first appeared in a Newsletter of the Kent and Sussex Microscopy Group, Spring 1993.


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