Rotifera is a moderately sized phylum of minute, bilaterally symmetrical, unsegmented animals that live predominantly in freshwaters. The phylum name (Latin, rota, wheel; ferre, to bear), first used by Cuvier in 1798, refers to the anterior end that in many species resembles a rotating wheel due to the sequential beat of its cilia. Rotifers have been found on every continent, occupying a diverse array of habitats, including marine, brackish and freshwaters, as well as the film of water that coats terrestrial mosses and particles in damp soils. In lakes rotifers often achieve high population densities (>1000 individuals per litre); thus, as consumers of bacteria, algae and protists they are ecologically important in transferring energy to higher trophic levels. As rotifers are a good food for young fishes, they are grown in mass quantities in commercial aquaculture. They also serve as models for research on ageing, and as bioindicators for ecotoxicology.

Key Concepts:

  • Rotifers have been found in the inland waters (both fresh and saline) of every continent, in the moisture covering some plants such as mosses, and in damp soil. Although generally not as abundant as in continental waters, rotifers often flourish in nearshore marine waters and estuaries.

  • Many rotifers are capable of undergoing dormancy, either as adults or embryos, allowing them to disperse in space or time and often avoid harsh conditions.

  • Feeding mainly on other microscopic organisms, including bacteria, algae and protists, rotifers are important basal consumers in aquatic systems.

  • In certain lakes, rotifers play an important role connecting the microbial loop to the classic food web, whereby the dissolved organic carbon is taken up by the bacteria that are consumed by rotifers, which in turn are consumed by higher trophic levels. In this way, a portion of the energy in dissolved organic matter is returned to the food web.

  • As they are the first food for larval organisms, rotifers have been exploited by aquaculturists to maintain commercially important fishes, shrimps and crabs.

  • As they are comparatively inexpensive and easy to culture and possess relatively short life spans, rotifers are used in ageing studies and to assess the toxicity of compounds such as heavy metals, pesticides and pharmaceuticals.

  • Some species of rotifers have specific ecological requirements making them useful as indicators of water quality.

  • The phylogenetic position of rotifers has not yet been resolved, but they appear to be related to a group of small, jawed metazoans (Gnathifera). Acanthocephala, an entirely parasitic phylum, are now considered to be highly aberrant rotifers.

  • Over the years rotifers have entered the collective culture ethos as subjects of poetry, science fiction and children's literature, artists' workings in glass and mixed media and pop music.

Keywords: anhydrobiosis; aquaculture; corona; diapause; eutely; intracytoplasmic lamina; parthenogenesis; syncytial; trophi

Figure 1.

Anatomy of a generalised rotifer. Reproduced with permission from Barnes, Calow and Olive .

Figure 2.

Asplanchna brightwellii – an illoricate, monogonont rotifer that is abundant in freshwater ponds. This raptorial species feeds on large algae, protists, other rotifers and small crustaceans. Bar, 100 μm.

Figure 3.

Limnias melicerta – a common, freshwater, sessile rotifer of subclass Monogononta that secretes a clear, firm tube. Although usually solitary, this illoricate species occasionally forms intraspecific colonies. Bar, 100 μm.

Figure 4.

Collotheca campanulata – a sessile rotifer lacking the typical ciliated corona of rotifers. The corona of this illoricate, raptorial species is highly modified into a funnel‐shaped structure termed the infundibulum. Bar, 100 μm.

Figure 5.

Macrotrachella sp. – a bdelloid rotifer with a corona divided into two separate wheel‐like structures called pedicels. Bar, 100 μm. Reproduced with the kind permission of Giulio Melone, University of Milan. © Giulio Melone.

Figure 6.

Hexarthra sp. – a planktonic rotifer with body projections (arms) that initiate rapid jumps that allow the animal to avoid predators. Bar, 100 μm.



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Wallace RL, Snell TW, Ricci C and Nogrady T (2006) Rotifera: Volume 1 Biology, Ecology and Systematics (2nd edn). In: Segers H (ed.) Guides to the Identification of the Microinvertebrates of the Continental Waters of the World, vol. 23, pp. 1–299. Ghent: Kenobi Productions; Leiden: Backhuys Publishers.

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Wallace, Robert Lee, and Smith, Hilary April(May 2013) Rotifera. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001588.pub2]