1. Ecological Significance
Rotifers are classified in the Phylum Rotifera, one of several phyla of lower invertebrates. The more than 2000 named rotifer species are divided into two classes: Pararotatoria and Eurotatoria, which houses the two major subclasses, Bdelloidea and Monogononta.1,2 Most species are monogononts and reproduce parthenogenetically; however, in response to specific environmental cues, they reproduce sexually, yielding dormant embryos called cysts (resting eggs), which have been used in toxicity testing.3 The use of rotifer cysts for toxicity testing has been discussed in the literature.3 Most rotifer species inhabit fresh water,4 but there are some genera, like Synchaeta, in which most species are marine.5 In coastal marine habitats, rotifers sometimes are the dominant portion of the biomass.6 They also are abundant in marine interstitial habitats, interstitial water of soils,7 and water clinging to mosses, liverworts, and lichens.8 In freshwater lake plankton9 and in river sediments,10 rotifers often are abundant, with high species diversity.
Rotifers play an important role in the ecological processes of many aquatic communities.11 As suspension feeders, planktonic rotifers influence algal species composition through selective grazing.12–14 Rotifers often compete with cladocera and copepods for phytoplankton in the 2- to 18-μm size range.15 Along with crustaceans, rotifers contribute substantially to nutrient recycling.16 Rotifers are food for many fish larvae.17