Rotifer
As a rotifer you would be a whole animal – brain, gut, muscles and all – packed into a body smaller than a grain of salt, with a crown of beating hairs that looks like a spinning wheel.
The wheel animal
Rotifers are microscopic animals, mostly 0.1–0.5 millimetres long, found in ponds, puddles, wet moss and soil water around the world; about 2,000 species are known. Despite their size, they have around a thousand cells, a simple brain, muscles, a stomach and a unique jaw called the mastax, which grinds food. Their head bears a corona, a ring of cilia whose beating looks like turning wheels – early microscopists including Antonie van Leeuwenhoek described these ‘wheel animalcules’ around 1700.
Your corona would create a current that sweeps bacteria, algae and organic particles into your mouth. Many species anchor themselves with a sticky foot while feeding, and some creep like leeches.
A family without males
Bdelloid rotifers are famous among biologists because no males have ever been found: the group appears to have reproduced asexually for tens of millions of years, with females laying eggs that develop into daughters. They seem to compensate partly by picking up foreign genes; a notable share of their genes appears to come from bacteria, fungi and plants. Other rotifers, the monogononts, mostly reproduce asexually but switch to producing small, short-lived males when conditions change, leading to tough resting eggs.
Drying, freezing, waiting
Bdelloids can dry out completely and revive when water returns, sometimes after years. In 2021 Russian researchers reported reviving bdelloid rotifers from Siberian permafrost radiocarbon-dated to about 24,000 years old. A normal active life is short, though – often one to a few weeks – and full of predators such as small crustaceans, insect larvae and other rotifers. Rotifers are also important food for fish fry, and aquaculture farms raise them in vast numbers.
