Animals

Mostly animals are multicellular,^[46] but some are too small to be seen by the naked eye. Microscopic arthropods includedust mites and spider mites. Microscopic crustaceansinclude copepods and the cladocera, while many nematodesare too small to be seen with the naked eye. Another particularly common group of microscopic animals are therotifers, which are filter feeders that are usually found in fresh water. Micro-animals reproduce both sexually and asexually and may reach new habitats as eggs that survive harsh environments that would kill the adult animal. However, some simple animals, such as rotifers and nematodes, can dry out completely and remain dormant for long periods of time.