Cyclops with Hitch-hikers

This little crustacean, about a millimetre long, is Cyclops, with a single red eye-spot in the centre of its head - a minute freshwater counterpart of the monocular monster of Greek mythology. My garden pond is swarming with them at present, even though the ice has barely thawed. If you take a close look at the top end of the tail, near the body, you can just make out clusters of short-stalked objects attached to the animal's exoskeleton. At higher magnification these turn out to be....

.......... Vorticellids - single celled protists with beating cilia around their mouth, creating a whirlpool current that sucks in foot particles. You can see a movie of Vorticella in action here. At even higher magnification..........

..you can see their cilia and the contractile vacuoles that they use to expel waste (double-click for a larger image). Vorticellids attach themselves to all sorts of small pond animals, hitching a ride.

As Jonathan Swift (1677-1745)  noted,

So, naturalists observe, a flea

Has smaller fleas that on him prey;

And these have smaller still to bite ’em;

And so proceed ad infinitum.

Pond Plankton

Mention the word ‘plankton’ and the drifting life in the surface layer of the oceans springs to mind – stuff that blue whales eat - but there’s plenty of plankton in the surface layer of lakes and ponds too. This picture (top) shows the larval stage – known as a nauplius – of a freshwater crustacean called a copepod (bottom photo), possibly Cyclops (that single red eye is a strong clue!). All those long bristles probably improve the nauplius larva's buoyancy, slowing the rate that it sinks and giving it extra leverage when it beats its limbs to stay in the surface layers. Copepod nauplius larvae go through a series of up to six moults before they become a recognisable Cyclops and this in turn goes through a further five moults before it reaches its final adult stage. The whole process takes the best part of a month, during which the nauplius and developing Cyclops are favourite food items on the menu of every passing predator; in this respect a nearly-mature tadpole is probably the blue whale of the pond. Life is hazardous when you’re small and edible!