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.

Mesocyclops pehpeiensis
Mesocyclops pehpeiensis
(a copepod)

Copyright Info
Mesocyclops pehpeiensis Hu, 1943

Common name: a copepod

Synonyms and Other Names: Mesocyclops Leuckarti pehpeiensis Hu, 1943, Mesocyclops ruttneri Kiefer, 1981, and Mesocyclops sp. (leuckarti group)

Taxonomy: available through www.itis.govITIS logo

Identification: The morphological features shared by most Asian species of Mesocyclops (absence of spines next to exopodal insertion on the antennal basipod, inner basis of first leg naked, seminal receptacle with lateral arms forming concave [or even V-shaped] margin) (Van de Velde 1984; Holynska 2000) are clearly present in M. pehpeiensis.

Antennula are 17-segmented with groups or rows of spinules on segment 1, 4, 5 and 7–13 and segment 17 with one deep notch. Antennary basis with caudal spinule pattern of M. leuckarti, row of 6–7 spinules at level of medial setae and 2–4 spinules near distal margin. Maxillulary palp without spinules. Maxillar syncoxa shows frontally distinct rows of spinules. Medial distal margin of P1 basis without spine. Distal margin of connecting
plate of P4 with two large acute outgrowths, medial expansion of P4 basis naked. Pediger 5 without hairs laterally and dorsally. Seminal receptacle with two short lateral arms, slightly curved at their ends and transverse ducts from copulatory pore slightly Vshaped.  Caudal rami without hairs on medial margin and armed with spinules at bases of lateral and external terminal setae.  Legs 1-3 have the inner margin of the basiopod haired (first leg is not naked), leg 4 basiopod is naked (Ueda and Reid 2003).


Size: to 1.7mm (US population max 1.52mm)

Native Range: Temperate and tropical areas of Asia. The native range of Mesocyclops pehpeiensis extends from Central Asia (South Kazakhstan, Uzbekistan) through India, South East Asia, China to the Japanese Islands (as far as Honshu). (Reid 1994; Kawabata & Defaye, 1994; Mirabdullayev et al., 1995; Mirabdullayev, 1996; Ueda & Ishida, 1997; Ueda et al., 1997).  Reports of the species from Malaysia (Lim and Fernando, 1985) and Sri Lanka (Dussart and Fernando, 1988) are apparently not conspecific with M. pehpeiensis according to Guo (2000)

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

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Mesocyclops pehpeiensis are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
DC199619961Middle Potomac-Anacostia-Occoquan
LA198719902Eastern Louisiana Coastal; Mermentau
MI201620182Lake Erie; Lake St. Clair
MS199119911Big Sunflower
OH201720183Cedar-Portage; Huron-Vermilion; Lake Erie

Table last updated 2/27/2023

† Populations may not be currently present.

Ecology: The overall known latitudinal range of this species extends roughly from 50°N to 7°S. In North America the known range of this species was established between 30 and 37°N (Reid 1993, 1996). The southernmost limit of the known distributional range of this species in the Americas was expanded with the Mexican record, setting the known meridional limit of M. pehpeiensis in the Americas at 14°N latitude. Lake Erie records from 2016 expand the known northern limit in the Americas to 42°N.  

According to Reid (1993), this species is more of an epibenthic form dwelling in the littoral zones. M. pehpeiensis is considered thermophilic (Anufriieva and Shadrin 2016).

Phong et al. (2008) report a mean longevity of 50.9 days across 19 female M. pehpeiensis with a mean clutch size of 90.6 eggs (sample size=100) and mean interclutch period of 1.5 days (sample size=27).

Mesocyclops species in general are voracious predators, feeding on rotifers, cladocerans, and dipteran larvae (Williamson 1986; Gliwicz and Umana 1994; Brandl 1998a, 1998b; Rao and Kumar 2002; Chang and Hanazato 2003; Kumar and Rao 2003; Dieng et al 2003; Nagata and Hanazato 2006; Sarma et al 2013). M. pehpeiensis is a omnivorous tactile predator (Dieng et al 2003) and will feed on phytoplankton in addition to zooplankton (Sarma et al 2013). In mesocosm experiments (Chang 2005) M. pehpeiensis restructured the zooplankton community.  The population of a small cladoceran, Bosmina fatalis, was affected negatively, but B. longirostris was not similarly affected. On the other hand, small rotifers responded positively to M. pehpeiensis.  In laboratory experiments, Hwang et al (2009) found M. pehpeiensis to severely supress the population growth of all four cladoceran species tested -- including rare Great Lakes native species Scapholeberis kingiiMesocyclops edax populations in DC ponds disappeared shortly after the discovery of M. pehpeiensis in those systems (Reid 1996).

Means of Introduction: Movement of this species is typically associated with the transfer of ornamental plants or aquaculture, or experimental biocontrol of mosquitos.  Introductions to Mexico were associated with prawn culture (Suarez-Morales et al 2005).  Anufiieva and Shadrin (2016) considered the Ukraine population to most likely have been introduced via long-distance transportation on birds.  Adults originally collected in New Orleans were introduced into Jennings ricefields in 1990 and into both Jennings and Cleveland ricefields in 1991 as part of mosquito-control experiments (G.G. Marten, personal communications, 1990, 1991 in USFWS 2018).”

Status: Established in the Great Lakes, but population currently local to western Lake Erie.   Densities appear low, but the species may avoid detection due to its preference for epibenthic and littoral habitats.  

Remarks: In Louisiana and Mississippi the species was initially reported as Mesocyclops sp. (leuckarti group) by Marten (1989), and later as M. ruttneri by Marten et al. (1993), Reid (1993), and Reid and Marten (1995). The District of Columbia population was also reported as M. ruttneri by Reid (1996).  The taxonomy and native distributions of this group is not well delineated ... this species may be native to North America (Hudson, Personal Communication 2019).  

References: (click for full references)

Anufriieva, E. V., and N. V. Shadrin. 2016. Current invasions of East Asian cyclopoids (Copepoda, Cyclopoida) in Europe: new records from eastern Ukraine. Turkish Journal of Zoology 40:282-285. http://journals.tubitak.gov.tr/zoology/issues/zoo-16-40-2/zoo-40-2-18-1507-16.pdf.

Brandl, Z. 1998a. Feeding strategies of planktonic cyclopoids in lacustrine ecosystems. Journal of Marine Systems 15:87-95. https://doi.org/10.1016/S0924-7963(97)00042-0.

Brandl, Z. 1998b. Life strategy and feeding relations of Cyclops vicinus in two reservoirs. International Review of Hydrobiology 83:381-388.

Chang, K. H., and T. Hanazato. 2003. Vulnerability of cladoceran species to predation by the copepod Mesocyclops leuckarti: laboratory observations on the behavioural interactions between predator and prey. Freshwater Biology 48:476-484. https://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2427.2003.01021.x.

Chang, KH. & Hanazato. 2005. Impact of selective predation by Mesocyclops pehpeiensis on a zooplankton community: experimental analysis using mesocosms.  T. Ecol Res 20:726. https://doi.org/10.1007/s11284-005-0089-y.

Díaz, Zulema Menéndez, Janet W. Reid, Ibian Castillo Guerra, and Ida Valdés Ramos. 2006. A new record of Mesocyclops pehpeiensis Hu, 1943 (Copepoda: Cyclopoida) for Cuba. Journal of Vector Ecology 31(1):193-195. https://doi.org/10.3376/1081-1710(2006)31[193:ANROMP]2.0.CO;2.

Dieng, H., M. Boots, N. Tuno, Y. Tsuda, and M. Takagi. 2002. A laboratory and field evaluation of Macrocyclops distinctus, Megacyclops viridis and Mesocyclops pehpeiensis as control agents of the dengue vector Aedes albopictus in a peridomestic area in Nagasaki, Japan. Medical and Veterinary Entomology 16(3):285-291.

Dieng, H., M. Boots, N. Tuno, Y. Tsuda, and M. Takagi. 2003. Life history effects of prey choice by copepods: implications for biocontrol of vector mosquitoes. Journal of the American Mosquito Control Association 19:67-73.

US Army Corps of Engineers (USACE).  2012.  Great Lakes Mississippi River Interbasin Study (GLMRIS).  2012.  

Gliwicz, Z. M., and G. Umana. 1994. Cladoceran body size and vulnerability to copepod predation. Limnology and Oceanography 39:419-424. https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1994.39.2.0419.

Guo X. 2000. A redescription of Mesocyclops pehpeiensis Hu, 1943 and notes on Mesocyclops ruttneri Kiefer, 1981 (Copepoda, Cyclopidae). Hydrobiologia 418: 33-43.

Holynska M., Reid J. W. & Ueda H. 2003.  Genus Mesocyclops Sars, 1914, in Ueda H. & Reid J. W. (eds), Copepoda: Cyclopoida genera Mesocyclops and Thermocyclops. Guides to the Identification of the Microinvertebrates of the Continental Waters of the World. 20. Backhuys, Amsterdam, 213 p.

Hwang, J.-S., R. Kumar, and C.-S. Kuo. 2009. Impacts of predation by the copepod, Mesocyclops pehpeiensis, on life table demographics and population dynamics of four cladoceran species: a comparative laboratory study. Zoological Studies 48(6):738-752.

Kawabata, K., and D. Defaye. 1994. Description of planktonic copepods from Lake Kahoku-gata, Japan. . Japanese Journal of Limnology 55:143-158. https://www.jstage.jst.go.jp/article/rikusui1931/55/2/55_2_143/_article.

Kiefer, F. 1981.  Beitrag zur Kenntnis von Morphologie, Taxonomie und geographischer Verbreitung von Mesocyclops leuckarti auctorum. Archiv für Hydrobiologie Supplement 62((1, Monographische Beiträge)):148-190. https://ci.nii.ac.jp/naid/10004881720/.

Kumar, R., and R. Rao. 2003. Predation on mosquito larvae by Mesocyclops thermocyclopoides (Copepoda: Cyclopoida) in the presence of alternate prey. . International Review of Hydrobiology 88:570-581. https://onlinelibrary.wiley.com/doi/abs/10.1002/iroh.200310631.

Marten, G. G. 1989.  A survey of cyclopoid copepods for control of Aedes albopictus larvae.  . Bulletin of the Society for Vector Ecology 14:232-236. http://gerrymarten.com/publicatons/pdfs/GM_Survey-of-Cyclopoid-Copepods.pdf.

Marten, G. G., W. Che, and E. S. Bordes. 1993. Compatibility of cyclopoid copepods with mosquito insecticides. Journal of the American Mosquito Control Association 9:150-154. http://www.gerrymarten.org/publicatons/pdfs/GM_Mosquito-Insecticides.pdf.

Mirabdullayev, I. M. 1996. The genus Mesocyclops (Crustacea: Copepoda) in Uzbekistan (Central Asia). International Review of Hydrobiology 81(1):93-100. https://onlinelibrary.wiley.com/doi/abs/10.1002/iroh.19960810111.

Mirabdullayev, I. M., T. S. Stuge, and A. R. Kuzmetov. 1995. On Mesocyclops ruttneri Kiefer, 1981 a species new to Kazakstan. Selevinia 2:31-32.

Montoliu, L., M. R. Miracle, and M. Elías-Gutiérrez. 2015. Using DNA barcodes to detect non-indigenous species: the case of the Asian copepod Mesocyclops pehpeiensis Hu, 1943 (Cyclopidae) in two regions of the world. Crustaceana 88:1323-1338. http://booksandjournals.brillonline.com/content/journals/10.1163/15685403-00003500/.

Nagata, T., and T. Hanazato. 2006. Different predation impacts of two cyclopoid species on a small-sized zooplankton community: an experimental analysis with mesocosms. . Hydrobiologia 556:233-242. https://link.springer.com/content/pdf/10.1007/s10750-005-1155-8.pdf.

Phong, T. V., N. Tuno, H. Kawada, and M. Takagi. 2008. Comparative evaluation of fecundity and survivorship of six copepod (Copepoda: Cyclopidae) species, in relation to selection of candidate biological control agents against Aedes aegypti.  24(1):61-69. Journal of the American Mosquito Control Association 24(1):61-69. http://www.bioone.org/doi/abs/10.2987/5672.1.

Rao, T. R., and R. Kumar. 2002. Patterns of prey selectivity in the cyclopoid copepod Mesocyclops thermocyclopoides. Aquatic Ecology 36:411-424. https://link.springer.com/content/pdf/10.1023/A:1016509016852.pdf.

Reid J. W. 1993. New records and redescriptions of American species of Mesocyclops and of Diacyclops bernardi (Petkovsky, 1986) (Copepoda, Cyclopoida). Bijdragen tot de Dierkunde 63: 173-191.

Reid J. W. 1996. Checklist of the Copepoda (Crustacea) of the District of Columbia. United States National Park Service “Bio Blitz”: http://www.im.nbs.gov/blitz/biocopewash.htm

Reid, J. W., and G. G. Marten. 1995. The cyclopoid copepod (Crustacea) fauna of non-planktonic continental habitats in Louisiana and Mississippi. Tulane Studies in Zoology and Botany 30:39-45.

Sarma, S. S., J. Jiménez-Contreras, R. Fernández, S. Nandini, and G. García-García. 2013. Functional responses and feeding rates of Mesocyclops pehpeiensis Hu (Copepoda) fed different diets (rotifers, cladocerans, alga and cyanobacteria) . Journal of Natural History 47:841-852. https://doi.org/10.1080/00222933.2012.747636.

Suárez-Morales E., Gutiérrez-Aguirre M. A., Torres J. L. & Hernández F. 2005. The Asian Mesocyclops pehpeiensis Hu, 1943 (Crustacea, Copepoda, Cyclopidae) in Southeast Mexico with comments on the distribution of the species. Zoosystema 27 (2) : 245-256.

Ueda, H., and T. Ishida. 1997. Species composition and description of limnoplanktonic copepods from Okinawa. Plankton Biology and Ecology 44:41-54. http://hdl.handle.net/10126/4684.

Ueda, H., T. Ishida, and J. Imai. 1997. Planktonic cyclopoid copepods from small ponds in Kyushu, Japan. II. Subfamily Cyclopinae. Hydrobiologia 356:61-71. https://link.springer.com/content/pdf/10.1023/A:1003155710590.pdf.

United States Fish and Wildlife Service (USFWS). 2018. Mesocyclops pehpeiensis (a cyclopoid copepod, no common name) Ecological Risk Screening Summary.

Van De Velde, I. 1984. Revision of the African species of the genus Mesocyclops Sars, 1914 (Copepoda, Cyclopidae). Hydrobiologia 109: 3-66.

Williamson, C. E. 1986. The swimming and feeding behavior of Mesocyclops. Hydrobiologia 134:11-19. https://link.springer.com/article/10.1007/BF00008695.

Author: R. Sturtevant

Revision Date: 9/12/2019

Peer Review Date: 9/5/2018

Citation Information:
R. Sturtevant, 2023, Mesocyclops pehpeiensis Hu, 1943: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=2794, Revision Date: 9/12/2019, Peer Review Date: 9/5/2018, Access Date: 3/21/2023

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.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2023]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [3/21/2023].

Contact us if you are using data from this site for a publication to make sure the data are being used appropriately and for potential co-authorship if warranted.

For general information and questions about the database, contact Wesley Daniel. For problems and technical issues, contact Matthew Neilson.