Intro to rotifers - Part 1

Rotifers are very small invertebrate crustaceans, typically between 100 microns to 500 microns, to put it into perspective that’s about the thickness of paper. Rotifers are found prominently in freshwater, but some species are found in saltwater, and on soil. Over the course of its evolution the phylum Rotifera have developed some unique traits that have allowed them to thrive in their environment; from multi reproduction methods, to body content and how it has become a vital part of many fish fry (baby fish) diets.

Rotifera has roughly 1500 to 2000 species inside of its phylum, this causes a lot of variation in between species, one of the key traits of rotifers across most species is the lack of males.  Rotifers vary between asexual reproduction, sexual reproduction or a mix of both, asexual reproduction occurs as females lay eggs that are very close clones of themselves. In the sexual reproduction of rotifers males exist for the sole purpose of fertilizing eggs (encyclopedia). Reproduction of rotifers can occur as quickly as every 18 hours, from the time they hatch. Females could lay “resting eggs” which simply means that the eggs will remain dormant if conditions are not right for the rotifers to hatch. In nature, the rotifers will typically produce these resting eggs alongside fertilized eggs with or without the presence of a male (Snell).

The ability of rotifers to have such a wide range of habitats from oceans, lakes, ponds, or even small puddles means that over hundreds of years rotifers have found it difficult to find mates to breed with and thus have gone on to depend on themselves in most cases. During an experiment, it was found that rotifers who either had a highly enriched diet or low nutrient diet became less sexual as time progressed compared to rotifers who had a change in diets (Pennisi). In the experiment by Pennisi, rotifers were feed a nitrogen enriched free floating algae as part of the enriched diet. Rotifers will feed on algae detritus, dead bacteria, and other things, all depending on the species and its size.

The ability of rotifers to breed is highly tied to its diet, but more importantly rotifers are a vital part of other predatory diets. There are many well researched articles on the use of rotifers in fry rearing because of the proteins and omega 3 fatty acids found in enriched rotifers.  Several peer reviewed articles also link improved growth rates in fish fry to diet enriched rotifers.  Corals will also benefit from rotifers as they extend their polyps at night which have nematocysts (stinging cells). The polyps help them feed on free floating algae, rotifers, cyclops, brine shrimp and other zooplankton organisms found in the water column.  SPS in particular benefit from rotifers; the small polyps and size of rotifers make them an ideal pairing.  Other animals such as fan worms will also feed on rotifers by filtering them from the water column directly.

Whether culturing your own rotifers, supplementing the biodiversity of your system, or using rotifers as a live food source to higher level predators, it’s very clear, rotifers are a critical and significantly important part of the food web and overall balance stability of marine ecosystems.



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Pennisi, E. "Evolutionary Time Travel." Science 334.6058 (2011): 893-95. Science. Web. 12 July 2017.

"Rotifera." Animal Sciences. . 5 Jul. 2017 <>.

Snell, Terry W., and Noah J.D. Desrosiers. "Effect of progesterone on sexual reproduction of Brachionus

manjavacas (Rotifera)." Journal of Experimental Marine Biology and Ecology, vol. 363, no. 1-2, 2008, p. 104+. Academic OneFile, Accessed 6 July 2017.

Sulehria, Abdul Qayyum Khan, and Muhammad Anwar Malik. "Evaluation of Rearing Cyprinus carpio Fry

on Freshwater Rotifer, Brachionus calyciflorus." Pakistan Journal of Zoology, vol. 44, no. 4, 2012. Academic OneFile, Accessed 6 July 2017.