With approximately 2000-2500 described species, the Rotifera is by far the largest of the gnathiferan taxa. All rotifers belong to the meiofauna which means that their sizes mostly range from 100 µm to 1000 µm. They are represented in both limnic, marine and terrestrial environments, and especially in fresh water they have been extremely successful both concerning species richness and number of individuals. The rotifer body is generally composed of a head, a trunk and a foot region, but the morphology varies greatly. The head carries bands of cilia forming the corona or wheel-organ which have given the group its name. In the head region we also find the mouth opening that lead to pharynx with its jaw apparatus. The morphology of the body integument may also vary greatly. Some groups, such as the Synchaetidae and Dicranophoridae, have a quite soft and flexible integument whereas others carry a heavy armour referred to as the lorica. Reproduction in rotifers follows a highly complicated cycle. It can either follow a sexual or an asexual cycle. During the asexual cycle the females are capable of producing daughters by parthenogenesis, allowing the population to grow very fast. Males are never involved in this part of the reproduction. When the asexual cycle switches to the sexual cycle, another type of females, the mictic females, are produced. The mictic females produce haploid eggs that can either produce a haploid dwarf male or wait until a dwarf male fertilizes it. The fertilized egg develops into a thick-shelled resting egg, which is capable of withstanding dehydration and other environmental stress factors. After the required stimuli an amictic female will hatch from the resting egg. The rotifer class Bdelloidea reproduce solely by parthenogenesis, whereas sexual reproduction is known from several other rotifers. Follow this link to read more about rotifers.