Nature Studies by Michael McCarthy: We've lost touch with the tiny, microscopic things

Ask your child what a tyrannosaurus is, or a velociraptor, and you'll probably get an intelligible answer. Movies have made dinosaurs familiar to millions. But ask them what a rotifer is, or a tardigrade, and you'll get a blank stare.

Yet 50 years ago, many boys and girls might have enlightened you, says Peter Marren, one of our leading naturalists. For tardigrades and rotifers are microscopic animals found in freshwater bodies, such as ponds, and were the delight of children with microscopes – now, says Mr Marren, virtually a vanished species.

Not just children, either. It's as if, he says, a whole, major part of the natural world has dropped out of our consciousness – microscopic life, the kingdom of the tiny. That's something he's an authority on, because two years ago he published Bugs Britannica, a fascinating encyclopaedia of Britain's invertebrates, the creatures without backbones, which are overwhelmingly insects, but also the very tiny things, such as daphnia or water fleas.

Nobody looks at them now, he laments. "Hardly anybody uses a microscope any more. They're just for specialist activities now, and there aren't many specialists, either. But half of biodiversity, you need a microscope to see! The teeming hordes of these things, which are everywhere. They're totally neglected now. Amateur naturalists tend not to bother with them. The sense of wonder you can get through seeing a world you can't otherwise see – that sort of curiosity seems to have vanished."

He certainly makes that world worth looking at in Bugs Britannica. Tardigrades, for example, are also known as water bears, as they "clamber about on their stumpy legs in an undeniably bear-like manner". To survive drought, they can shrivel up and dry out – "and in this state, the water bear's life processes come to a complete stop, and... it can survive almost any conditions." He instances boiling water, pressure greater than the deepest ocean, irradiation worse than a microwave oven, total asphyxiation, freezing in liquid nitrogen, immersion in toxic chemicals, and, for a clincher, being taken into orbit by the European Space Agency, so that tardigrades are "the first animals to have been exposed to the vacuum of space and unprotected solar radiation, and lived". A single drop of water revives them.

Rotifers are another intriguing part of pond life; many are transparent, so all their internal organs can be seen. "Despite being no bigger than protozoa, a rotifer is a multi-cellular wonder of miniaturisation," Mr Marren writes. "It has a nervous system as well as a digestive gut, sex organs, a heart and a brain, all packed into a space smaller than a full stop."

Who looks at them now? Modern field guides on pond life, Mr Marren complains, have three or four plates on the microscopic side of it, whereas once they had dozens. "A lot of kids had microscopes then, but kids don't have microscopes any more. It's also that ponds are disappearing; every farmer's field had a pond in the corner, but most of them have gone.

The scientists who can't see the fish for the genes

The loss of general familiarity with the microscopic world can, in fact, be seen as part of a bigger picture; the decline of "whole-organism biology". In the past half century, traditional natural history, the study of animals and plants for themselves, has come to be seen as more and more divorced from the cutting edge of science, indeed, it has come to be despised as merely one step up from stamp collecting; what is now sexy, in scientific terms, is molecular biology, the study of an animal's genes.

I once met a marine biologist from Plymouth who complained that he knew scientists who could tell you everything you wanted to know about the genomes of fish, but if you handed them an unusual fish species brought back by a trawler, they wouldn't have a clue what it was.

m.mccarthy@independent.co.uk