Though they are generally the size of the protozoa, the single celled animals, they are multi- celled and so form part of the metazoa, being one of the five main classes of round worms. Worldwide there are around 2,000 species, of which there are over 500 in Britain, with a great variety of body forms. They are also found in damp soil, in damp moss, and in fact in any place where there is even only a little water, particularly in house or garage rainwater gutters that tend to hold some water for a time before it evaporates, where in their dried-up state, like most water living micro organisms, they can survive being baked during long hot and dry summers, quickly resuming their full lives when damp or wet conditions return. The bodies of many species of rotifers are transparent and in their living state you can see their internal organs. After death the bodies tend to cloud over.
Most rotifers are females.
Males are few and not able to feed, living not more than a few days. Rotifers were first discovered by Leeuwenhoek some 200 years ago and he explained how wonderfully nature has provided for the preservation of the species by their resistance to the drying up of their abodes and their resulting desiccation until moisture returns again. He wrote We can easily conceive that in all rainwater which is collected from gutters and in all waters exposed to the air, animals may be found, for they may be carried thither by the particles of dust blown about by the winds. These fascinating animals are ever so easy to find. Try taking a little of the dried mud or leaf litter found in house, garage and outhouse gutters, put it in a little water and leave for 24 hours.