Monogononta is a class of

rotifer The rotifers (, from Latin 'wheel' and 'bearing'), sometimes called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic Coelom#Pseudocoelomates, pseudocoelomate animals. They were first describ ...

s, found mostly in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

but also in

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

and marine environments. They include both free-swimming and sessile forms. Monogononts generally have a reduced corona, and each individual has a single

gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...

, which gives the group its name. Males are generally smaller than females, and are produced only during certain times of the year, with females otherwise reproducing through

parthenogenesis Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

. Their mastax is not designed for grinding. They produce mictic and amictic eggs. The class contains 1,570 species. Females are always diploid, and males are haploid. Diploid females produce two types of eggs. One type give rise to new females like themselves, and another that give rise to females that only produce haploid eggs. These will develop into males. When males, through hypodermic impregnation, inject sperm into the body cavity of females carrying a haploid egg, the fertilized egg will develop into diploid resting eggs that can remain in diapause for days to many years, before they hatch into new diploid females that can produce two types of females. But there are some exceptions from the rule: A few females can produce both diploid and haploid eggs, and the female in a couple of species can produce morphologically distinct diploid eggs through parthenogenesis that undergo diapause. Other types, like Asplanchna, are ovoviviparous, where eggs develop and hatch in the uterus.Variation in the life cycle of monogonont rotifers: Commitment to sex and emergence from diapause
/ref>

References

External links

Rotifer World Catalog, by C.D. Jersabek & M.F. Leitner
Eurotatoria Protostome classes {{rotifer-stub