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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: a rotifer

Synonyms and Other Names: Brachionus quadratus Rousselet, 1889; Brachionus reticulatus Kertész, 1894; Brachionus quadratus rotundus Rousselet, 1907; Brachionus quadratus tridentatus Zernov, 1901

Taxonomy: available through www.itis.gov

Identification: Brachionus leydigii is a nearly square rotifer, with a body divided into three dorsal, ventral, and basal plates. The anterior dorsal margin has six spines of nearly equal length, with median spines slightly longer and curving somewhat ventrally. Small spines are usually present at the joint of the dorsal and basal plates. A large circular or club shaped foot opening is visible on the dorsal surface. The body wall of B. leydigii is firm and slightly raised toward the center (Leasi 2012).

Size: Total length 220-280 µm; maximum width 165 µm

Native Range: Afrotropical, Australian, Oriental, and Palearctic biogeographical regions (Segers 2007)

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Rotifers live mainly among aquatic vegetation in the littoral zone of lakes, ponds, rivers, canals, pools, and other small water bodies. Due to the absence of respiratory organs, this species uses its entire body surface to respire and is therefore unable to live in anaerobic conditions (Sladecek 1983). Most communities contain 50 to 500 individuals per liter, with the densest population reported in unpolluted water reaching 5,800 individuals per liter (Smith 2001). Brachionus ledygii filter feeds on small material such as bacteria and detritus and is able to selectively filter particles by size with a corona of cilia surrounding its mouth (Wallace 2002). Experiments on the rotifer composition among different lakes types suggest that Brachionus spp. thrive primarily in eutrophic environments and are largely absent from oligotrophic and mesotrophic areas (Maemets 1983, Sladecek 1983).

With large population sizes and high turnover rates, rotifers are significant contributors to lake food webs (Herzig 1987, Starkweather 1987, Walz 1997). Additionally, rotifers are the first food of fish fry and are eaten by a variety of invertebrate predators, leading to the assimilation of their energy into higher trophic levels (Wallace 2002). Rotifers may also play a role in microplankton community structure, although the magnitude of their importance is unknown (Arndt 1993, Berninger et al. 1993, Rublee 1998). The study of rotifer population dynamics is challenging, as annual species abundance across a variety of habitats can vary greatly (Herzig 1987).

Rotifers’ annual reproductive cycle involves both sexual and asexual stages. The asexual phase involves amictic (parthenogenic) females who produce mitic haploid eggs in autumn, from which males hatch without fertilization. Males typically only live for a few hours, dying immediately after reproduction (Sladecek 1983). The sexual phase results in resting stage “winter eggs” that develop with a thick protective cover resistant to desiccation and extreme thermal conditions (Clement and Wurdak 1991, Sladecek 1983, Wurdak et al. 1978). After production, these diapausing eggs sink to the sediment where they can remain viable for several decades (Kotani et al. 2001, Marcus et al. 1994). When favorable conditions return, eggs complete their development; however, a fraction will remain viable and accumulate in the sediment, forming resting egg banks (Garcia-Roger et al. 2005). These egg banks may help to ensure survival through unfavorable environmental conditions as well as possibly act as a dispersal device (Fryer 1996, Garcia-Roger et al. 2005, Hairston 1996, 1998, Ortells et al. 2000, Templeton and Levin 1979). Anoxia or low oxygen levels in the sediment, however, may lead to low viability of diapausing eggs (Lutz et al. 1994, Uye et al. 1984).

Means of Introduction: Shipping (Ballast Sediment)

Status: Unknown. Although only a single individual was collected, rotifer reproductive biology includes an asexual reproductive stage and diapausing eggs (see Ecology section above). In order to be considered an established species a reproducing population must be present within the basin. A reproducing population is inferred from multiple discoveries of adult and juvenile life stages over at least two consecutive years.

Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.

References: (click for full references)

Arndt, H. 1993. Rotifers as predators on components of the microbial web. Hydrobiologia 255: 231-246.

Berninger, U.G., S.A. Wickham, and B.J. Finlay. 1993. Trophic coupling within the microbial food web: A study with fine temporal resolution in a eutrophic freshwater ecosystem. Freshwater Biology 30: 419-432.

Clement, P., and E. Wurdak. 1991. Rotifera. In: F.W. Harrison and E.E. Ruppert, eds. Microscopic anatomy of invertebrates. Volume 4. Aschelminthes. Wiley-Liss, New York, NY. pp. 219-297.

Code of Federal Regulations Title 33. 2012. Part 151- Vessels carrying oil, noxious liquid substances, garbage, municipal or commercial waste, and ballast water. Subparts C and D. Available https://www.gpo.gov/fdsys/granule/CFR-2012-title33-vol2/CFR-2012-title33-vol2-part151

U.S. Environmental Protection Agency (USEPA). 2017. Brachionus leydigii. https://www.epa.gov/great-lakes-monitoring/brachionus-leydigii. Created on 08/14/2017. Accessed on 08/14/2017.

Fryer, G. 1996. Diapause, a potent force in the evolution of freshwater crustaceans. Hydrobiologia 320: 1-14.

Garcia-Roger, E.M., M.J. Carmona, and M. Serra. 2005. Deterioration patterns in diapausing egg banks of Brachionus (Muller, 1786) rotifer species. Journal of Experimental Marine Biology and Ecology 314: 149-161.

Hagiwara, A., M.D. Balompapueng, N. Munuswamy, and A. Hirayama. 1997. Mass production and preservation of resting eggs of the euryhaline rotifer Brachionus plicatilis and B. rotundiformis. Aquaculture 155: 223-230.

Hairston, N.G., Jr. 1996. Zooplankton egg banks as biotic reservoirs in changing environments. Limnology and Oceanography 41: 1087-1092.

Hairston, N.G., Jr. 1998. Time travelers: what’s timely in diapause research? Archive for Hydrobiology Special Issues Advances in Limnology 52: 1-15.

Herzig, A. 1987. The analysis of planktonic rotifer populations: A plea for long-term investigations. Hydrobiologia 147: 163-180.

Kotani, T., M. Ozaki, K. Matsuoka, T.W. Snell, and A. Hagiwara. 2001. Reproductive isolation among geographically and temporally isolated marine Brachionus strains. Hydrobiologia 446/447: 283-290.

Leasi, F. 2012. Brachionus leydigii. Marine Rotifera LifeDesk. Available http://rotifera.lifedesks.org/pages/341. Accessed 18 June 2012.

Lutz, R.V., N.H. Marcus, and J.P. Chanton. 1994. Hatching and viability of copepod eggs at two stages of embryological development: anoxic/hypoxic effect. Marine Biology 119: 199-204.

Maemets, A. 1983. Rotifers as indicators of lake types in Estonia. Hydrobiologia 104: 357-361.

Marcus, N.H., R. Lutz, W. Burnett, and P. Cable. 1994. Age, viability, and vertical distribution of zooplankton resting eggs from an anoxic basin: evidence of an egg bank. Limnology and Oceanography 39(1): 154-158.

Rublee, P. 1998. Rotifers in arctic North America with particular references to their role in microplankton community structure and response to ecosystem perturbations in Alaskan Arctic LTER lakes. Hydrobiologia 387/388: 153-160.

Segers, H. 2007. Annotated checklist of the rotifers (Phylum Rotifera), with notes on nomenclature, taxonomy and distribution. Zootaxa 1564:1-104. http://www.mapress.com/zootaxa/2007f/zt01564p104.pdf.

Sladecek, V. 1983. Rotifers as indicators of water quality. Hydrobiologia 100: 169-201.
Smith, D.G. 2001. Pennak’s freshwater invertebrates of the United States: Porifera to Crustacea. 4th Edition. Wiley. 648 pp.

Starkweather, P.L. 1987. Rotifera. In: T.J. Pandian and F.J. Vernberg, eds. Animal energetics. Volume 1, Protozoa through Insecta. Academic Press, Orlando, FL. pp. 159-183.

Templeton, A.R., and D.A. Levin. 1979. Evolutionary consequences of seed pools. American Naturalist 114: 232-249.

Uye, S., K. Yoshiya, K. Ueda, and S. Kasahara. 1984. The effect of organic sea-bottom pollution on survivability of resting eggs of neritic calanoids. Crustaceana supplement 7: 390-403.

Wallace, R.E. 2002. Rotifers: exquisite metazoans. Integrative and Comparative Biology 42: 660-667.

Walz, N. 1997. Rotifer life history strategies and evolution in freshwater plankton communities. In: B. Streit, T. Stadler, and C.M. Lively, eds. Evolutionary ecology of freshwater animals. Birkhauser Verlag, Basel. pp. 119-149.

Wurdak, E.S., J.J. Gilbert, and R. Jagels. 1978. Fine structure of the resting eggs of the rotifers Brachionus calyciflorus and Asplanchna sieboldi. Transactions of the American Microscopical Society 97(1): 49-72.

Author: Baker, E., Dettlof, K., Fusaro, A., and Hopper, K.

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.