This website uses cookies to provide a rich user experience. Please consult our Cookie Policy to learn about what cookies this website uses, or to control the cookies you receive. You need do nothing if you are happy to receive cookies.
Look and Learn History Picture Library License images from £2.99 Pay by PayPal for images for immediate download Member of British Association of Picture Libraries and Agencies (BAPLA)

Minuscule creatures in the garden pond

Posted in Biology, Nature, Science on Wednesday, 6 February 2013

Click on any image for details about licensing for commercial or personal use.

This edited article about amoeba originally appeared in Look and Learn issue number 118 published on 18 April 1964.

crustaca, picture, image, illustration

Crustacea with the distinctive cyclops (centre)

When you look in a pond it seems to be alive with sticklebacks and minnows, tadpoles and newts, water beetles and snails. They seem very tiny indeed and there are a lot of them.

But if you examine a drop of water from the pond through a microscope you see a world of creatures tinier than the smallest fish or insect.

In this crowded, busy little world every speck of life keeps its microscopic body alive by feeding and by taking in oxygen and giving out carbon dioxide to “breathe” as do fish and land animals.

Every living thing in the drop of pond water is continually on the move. Some move slowly as though feeling their way about. Others cross and re-cross and dart backwards and forwards in a flurry of activity. You might be at the top of a skyscraper watching a street during the rush hour instead of looking at a drop of water.

Smallest of all these microscopic creatures are the amoeba, which are the most simple forms of animal life. There are several kinds of amoeba but each consists of a single speck of jelly-like substance which must be magnified about a hundred times by the microscope to be seen.

Some amoeba propel themselves through the water by means of minute, hair-like threads called cilia. These are constantly vibrating and set up currents in the water to push the midgets along. Other amoeba move about by pushing out from their bodies microscopic projections of jelly called pseudopodia, which cause them to glide or flow across the surface of the water.

Then there is the paramoecium, sometimes called the slipper animalcule because of its shape. A procession of two hundred of them marching in single file would be less than an inch long. Despite its small size, the paramoecium is covered with a kind of shell called a pellicle.

Another midget of the pond water is the bell-shaped vorticella. It has a tiny stalk or stem with which it attaches itself in colonies of several thousand to water weeds. You would hardly notice a colony of vorticella with the naked eye.

One of the strangest groups of creatures seen moving about under the microscope is the flagellata. Flagellata comes from the Latin word flagetum, meaning whip, and is given to the creature because of its long, thread-like appendage or tail. It whips the water with its tail, so propelling itself at an amazing speed. Flagellata are green in colour with a single red spot, which biologists believe to be some kind of eye.

Among the most common form of life in pond water are the volvox. These cling together in colonies of several hundreds and the whole colony moves about by slowly revolving through the water. A colony of several hundred magnified fifty times would be less than a quarter of an inch in diameter.

Moving up the scale there are creatures which, although they can be seen with the naked eye, must be observed through a microscope to see any details of their anatomy.

One of these giants is the hydra. Its body is shaped like a cylinder and has at one end a sucking disc with which it attaches itself to a water weed or to the bottom of the pond. At the other end of the hydra’s body is its mouth, surrounded by thin, hair-like tentacles.

With its tentacles slowly waving in the water, the hydra lies waiting for any creature smaller than itself to swim or drift past. Immediately a victim touches a tentacle it is poisoned and paralysed and then pushed by the tentacles into the hydra’s mouth.

Most of the hydra’s victims are minute creatures called crustacea. They are the microscopic relatives of the crabs and lobsters, which they resemble by having shells and jointed limbs.

They are fascinating to watch as they pass across the lens of a microscope. When a strong light is thrown up by the mirror beneath the microscope platform, their whole anatomy is seen.

Very often a tumbler of water dipped from a pond has a reddish-brown tinge caused by the presence of daphnia.

More commonly called water fleas, daphnia are oval in shape, nearly red in colour, and their bodies are enclosed in a shell like that of a crab – but infinitely thinner and smaller. Projecting from the body are tentacle-like arms with which it paddles its way about in the water.

Closely related to daphnia are the cyclops. They also have oval-shaped bodies and swimming tentacles, but they are much smaller than daphnia and travel about much more quickly. A cyclops has a single eye and gets its name from Cyclops, the one-eyed giant of Greek mythology.

Both daphnia and cyclops breathe through their feet or swimming tentacles. At the end of each tentacle is a gill, not unlike that of a fish, with which they extract oxygen from the water.

Cyclops and daphnia are the oldest forms of life in the world and are descendants of the ancient trilobite.

Leave a comment

You must be logged in to post a comment.