Bdelloid rotifers are multiclellular microscopic critters with some very unique features. Most of them live in mosses or soil, an environment with little water, where they live in a thin film of water covering the moss leafs or small grains of sand or humus.

They are survival artists, they can survive years of desiccation and also are able survive lowest temperatures, for example in liquid nitrogen. Now scientisst have found them (alive!!!) in Siberian permafrost which has been shown to be frozen for 24000 years. Also exposition to ionizing radiation in space does not affect them. They have been found all around the globe, in hot deserts, in polar regions, but also in coffee machines or shower heads.

Another striking feature of belloid rotifers is that no males exist since millions of years; there are only females which reproduce by parthenogenesis, i.e. they produce daughters either by unfertilized eggs or by vivipary.

Because of this obligate pathenogenesis the classical species concept does not work; therefore also the species identification is very problematic: most of the "variations" that are listed in the literature of the early rotiferologists are probably "species" by today´s standards. There are some very good keys for the identification of bdelloid taxa; here is a key based on special features of certain rotifers that may help to delimit the numbers of potential species.