rotatoria

Rotatoria, historically used as a name for the wheel-bearing animals of the phylum Rotifera, refers to a group of microscopic aquatic animals found in freshwater, brackish, and marine environments, as well as in damp soil and plant matter. Modern taxonomy generally uses Rotifera as the accepted phylum name, while Rotatoria remains common in older literature. The group comprises thousands of described species, with a broad geographic distribution and ecological diversity.

Anatomy and biology

Rotifers are typically small, ranging from about 50 to 500 micrometers. A defining feature is the corona, a ring of ciliated discs that beats in a circular pattern to create water currents and capture food. This ciliary wheel, or “wheel organ,” is part of a complex feeding apparatus centered on the mastax, which contains trophi (jaw-like structures) for grinding food. The body is usually elongated or spherical and may be protected by a lorica in some species; many rotifers have a pseudocoelom and a syncytial epidermis. They are primarily suspension feeders, consuming microalgae, bacteria, and detritus. Reproduction and life cycles are diverse: many Monogononta reproduce mostly by parthenogenesis, while Bdelloidea include long-term asexual lineages with resting eggs; some species switch to sexual reproduction under stress.

Ecology and significance

Rotifers occupy a key position in aquatic ecosystems, forming an important component of zooplankton and contributing to the microbial loop. They can be indicators of water quality and are used in ecotoxicology and toxicology testing due to their sensitivity to pollutants. Rotifers also serve as prey for small invertebrates and fish and, in aquaculture, provide appropriate live feed in larval rearing.

Taxonomic note

Rotifera comprises three main classes: Monogononta, Bdelloidea, and Seisonidea. Seisonidea are relatively small and often parasitize marine crustaceans. The term Rotatoria is largely historical, whereas Rotifera is the preferred scientific designation today.