Larvae feed on aquatic insect larvae, protozoa, rotifers or small crustaceans. Tardigrades, some rotifers and some copepods are able to withstand desiccation as adult dormant stages. Other dominating inhabitants of the river are protozoa, rotifers, Cladocera and copepods. Eukarya are also found, including some multicellular life (nematodes, fungi, flatworms, rotifers, annelids and arthropods). Other organisms eaten include other fly larvae, insect eggs, rotifers and testate amoebae. Carnivorous species maintain populations of small invertebrates such as nematodes, rotifers, and other collembolan species. They feed on phytoplankton, but mostly on small crustaceans, rotifers, and insects and their larvae. Brachionus is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. It typically feeds on other small organisms such as algae, rotifers, and nematodes. Some nematodes and rotifers can also undergo cryptobiosis. A few small animals (nematodes, tardigrades, and rotifers) live in the river. In populations of bdelloid rotifers, however, many parasites are destroyed during periods of extended desiccation. In 2003, the mode of asexual reproduction in the bdelloid rotifers was wholly unknown. About 2200 species of rotifers have been described. The Rotifera or rotifers, are common in aqueous environments.