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.

Megacyclops viridis
Megacyclops viridis
(a cyclopoid copepod)

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Megacyclops viridis Jurine, 1820

Common name: a cyclopoid copepod

Synonyms and Other Names: Acanthocyclops viridis

Taxonomy: available through www.itis.govITIS logo

Identification: In adult females of this copepod the distal segment of the 5th leg exhibits one spine, located distally or subdistally. This spine is equal to or shorter than 1/5 the length of the seta that is also present. The distal segment of the 5th leg also has a spine or spur on the inner margin located in the middle of the segment. The interior of the caudal rami is covered with hairs. Adult females’ antennules consist of 11–17 segments. The length to width ratio of this species is anywhere from 3.2.–4.4. The length to width ratio of the furcal branches is around 3.5–4.5 (Einsle 1988; Williamson 1991; Hudson et al. 1998; Schutze et al. 2000).

Size: can grow to around 1.2–3 mm in length (Einsle 1988; Williamson 1991)

Native Range: Megacyclops viridis is found throughout the Holarctic, but is mostly considered a European species (Hudson et al. 1998; Grigorovich et al. 2003).

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

Nonindigenous Occurrences: Megacyclops viridis is present in Duluth Harbour, Lake Superior, where the St. Louis River forms an estuary as it joins the lake. It was probably introduced around 1994. It has been recorded from the Canard River drainage, which is part of the western Lake Erie basin. There are earlier records from Lake Superior and Lake Erie, but they were probably in error and referred to other members of the Acanthocyclops vernalis-complex (Ogle et al. 1995; Hudson et al. 1998; Grigorovich et al. 2003).

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 Megacyclops viridis are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
MN199419941Lake Superior

Table last updated 4/22/2024

† Populations may not be currently present.

Ecology: Megacyclops viridis can survive in Austria in salt ponds at sodium concentrations up to 7.9 g/l and conductivity of 10,210 μS/cm. Megacyclops viridis is often associated with the presence of macrophytes. It is frequently found at the surface at night and at the bottom amongst macrophytes during the day. In the littoral zone where it tends to occur there is often a high humic content resulting from inputs of allochthonous material. Megacyclops viridis can tolerate moderately eutrophic water. It can also occur in groundwater as a stygoxen. Megacyclops viridis can also tolerate oxygen saturation as low as 25% for 4 days, but it experiences rapid mortality in total anoxia (Szlauer 1963; Armengol 1978; Pesce and Maggi 1981; Tinson and Laybourn-Parry 1985; Einsle 1988; Berzins and Bertilsson 1990; Hansen and Jeppesen 1992; Wolfram et al. 1999; Baranya et al. 2004).            

Megacyclops viridis lives for around 100–300 days. The time to the first clutch is 8–75 days and the inter-clutch period is around 5–18 days. In each clutch it produces around 59–153 eggs and the embryos develop in 4–22 days. All these values vary with temperature. At 20ºC, the life history phases are shorter, while they take longer at 5ºC. Megacyclops viridis populations may go through cyclic fluctuations. For example, in a reservoir in Spain, the population is often absent in late winter and mid-summer. In a lake in Iceland, populations peak in July and August. There may be marked seasonal size differences. For example, larger individuals may occur in winter and early spring while smaller ones may be present in summer and fall (Cruz and Martinez 1976; Adalsteinsson 1979; Einsle 1988; Abdullahi 1990).

Megacyclops viridis can feed on such prey items as algae, protozoans, ciliates, cladocerans, and various crustacean nauplii. It can prey on mosquito larvae and has been considered for use in control of dengue-carrying mosquitoes, Aedes albopictus (Abdullahi 1992; Dieng et al. 2002).            

Megacyclops viridis is a host to many parasites in its native range, some of which include: the eel tapeworm Bothriocephalus claviceps; the widespread snake parasite Ophiotaneia europaea; the nematode Philometra abdominalis; and the euglenoid parasites Embryocola diflagellatus and Dinema symmetricum (Michajlow 1969; Michajlow and Wita 1976; Moravec 1977; Biserkov and Genov 1988; Scholz 1997).

Means of Introduction: Megacyclops viridis was very likely introduced in ballast water in ships entering the Great Lakes (Hudson et al. 1996).

Status: Established in the Lake Erie drainage and the mouth of the St. Louis River in Lake Superior.

Impact of Introduction:

A) Realized: Megacyclops viridis is an important prey item for various size classes of introduced ruffe (Gymnocephalus cernuus) (Ogle et al. 1995).  

B) Potential: Unknown.

Remarks: Grigorovich et al. (2003) indicate that M. viridis is native to the Great Lakes basin due to its widespread distribution throughout the Holarctic region, but Hudson et al. (1998) disagree, mentioning that its appearance within the past couple of decades and the mistaken historical records suggest a relatively recent introduction to the Great Lakes.

Megacyclops viridis has been reported as a potential biocontrol of dengue-carrying mosquitos (Blaustein and Margalit 1994, Dieng et al. 2002, Fryer 1957).

References: (click for full references)

Abdullahi, B.A. 1990. The effect of temperature on reproduction in three species of cyclopoid copepods. Hydrobiologia 196: 101-109.

Abdullahi, B.A. 1992. Effects of diet on growth and development of three species of cyclopoid copepods. Hydrobiologia 232: 233-241.

Adalsteinsson, H. 1979. Seasonal variation and habitat distribution of benthic Crustacea in Lake Myvatn, Iceland in 1973. Oikos 32(1-2): 195-201.

Armengol, J. 1978. Zooplankton crustaceans in Spanish reservoirs. Proceedings: Congress in Denmark 1977 Part 3: Internationale Vereinigung fur Theoretische und Angewandte Limnologie 20: 1652-1656.

Baranya, E., L. Forro, and A. Herzig. 2004. Species composition and seasonal dynamics of cladoceran and copepod zooplankton in artificial sodic ponds. Archives des Sciences (Geneva) 57(2-3): 113-120.

Berzins, B., and J. Bertilsson. 1990. Occurrence of limnic micro-crustaceans in relation to pH and humic content in Swedish water bodies. Hydrobiologia 199: 65-71.

Biserkov, V., and T. Genov. 1988. On the life cycle of Ophiotaenia europaea Odening 1963 (Cestoda: Ophiotaenidae). Khelmintologiya 25: 7-14.

Blaustein, L., and J. Margalit. 1994. Differential vulnerability among mosquito species to predation by the cyclopoid copepod, Acanthocyclops viridis. Israel Journal of Zoology 40(1): 55-60.

Cruz, L., and R. Martinez. 1976. Limnological study of the Cubillas reservoir near Granada, Spain. 2. Seasonal distribution and daily cycle of planktonic crustaceans. Cuadernos de Ciencias Biologicas Universidad de Granada 5: 87-108.

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. 

Einsle, U. K. 1988. Taxonomy of the genus Megacyclops (Crustacea, Copepoda): morphometry and the use of enzyme electrophoresis. Hydrobiologia 167/168: 387-391.

Fryer, G. 1957. The food of some freshwater cyclopoid copepods and its ecological significance. Journal of Animal Ecology 26(2):263-286.

GLMRIS. 2012. Appendix C: Inventory of Available Controls for Aquatic Nuisance Species of Concern, Chicago Area Waterway System. U.S. Army Corps of Engineers.

Grigorovich, I.A., R.I. Colautti, E.L. Mills, K. Holeck, A.G. Ballert, and H. J. MacIsaac. 2003. Ballast-mediated animal introductions in the Laurentian Great Lakes: retrospective and prospective analyses. Canadian Journal of Fisheries and Aquatic Sciences 60: 740-756.

Hansen, A.M., and E. Jeppesen. 1992. Changes in the abundance and composition of cyclopoid copepods following fish manipulation in eutrophic Lake Vaeng, Denmark. Freshwater Biology 28(2): 183-193.

Hudson, P.L., J. W. Reid, L.T. Lesko, and J.H. Selgeby. 1998. Cyclopoid and harpacticoid copepods of the Laurentian Great Lakes. Ohio Biological Survey Bulletin New Series 12(2):i-vi + 1-50.

Michajlow, W. 1969. Dinema symmetricum, new species Euglenoidina, parasite of Copepoda from Poland. Bulletin de l’Academie Polonaise des Sciences Serie des Sciences Biologiques 17(8): 495-498.

Michajlow, W., and I. Wita. 1976. Embryocola diflagellatus, new species Euglenoidina, parasite of Copepoda from the environs of Warsaw, Poland. Bulletin de l’Academie Polonaise des Sciences Serie des Sciences Biologiques 24(10): 615-618.

Moravec, F. 1977. The development of the nematode Philometra abdominalis in the intermediate host. Folia Parasitologica (Ceske Budejovice) 24(3): 237-245.

Ogle, D.H., J.H. Selgeby, R.M. Newman, and M.G. Henry. 1995. Diet and feeding periodicity of ruffe in the St. Louis River estuary, Lake Superior. Transactions of the American Fisheries Society 124: 356-369.

Pesce, G.L., and D. Maggi. 1981. Cyclopoids and calanoids of the underground waters of southern Greece and some islands of Greece (Crustacea, Copepoda). Ecologia Mediterranea 7: 163-182.

Scholz, T. 1997. Life cycle of Bothriocephalus claviceps, a specific parasite of eels. Journal of Helminthology 71(3): 241-248.

Schutze, M. L. M., C. E. Rocha, and G. A. Boxshall. 2000. Antennulary development during the copepodid phase in the family Cyclopidae (Copepoda, Cyclopoida). Zoosystema 22(4): 749-806.

Szlauer, L. 1963. Diurnal migrations of minute invertebrates inhabiting the zone of submerged hydrophytes in a lake. Aquatic Sciences Research Across Boundaries 25(1): 56-64.

Tinson, S., and J. Laybourn-Parry. 1985. The behavioural responses and tolerance of freshwater benthic cyclopoid copepods to hypoxia and anoxia. Hydrobiologia 127(3): 257-264.

Williamson, C.E. 1991. Copepoda. Pp. 787-822 in J.H. Thorp and A.P. Covich, eds. Ecology and Classification of North American Freshwater Invertebrates. Academic Press, Inc., San Diego, California. 911 pp.

Wolfram, G., K. Donabaum, M. Schagerl, and V.A. Kowarc. 1999. The zoobenthic community of shallow salt pans in Austria – preliminary results on phenology and the impact of salinity on benthic invertebrates. Hydrobiologia 408-409: 193-202.

Other Resources:
Great Lakes Water Life

Author: Kipp, R.M., J. Larson, T.H. Makled, and A. Fusaro

Revision Date: 9/12/2019

Citation Information:
Kipp, R.M., J. Larson, T.H. Makled, and A. Fusaro, 2024, Megacyclops viridis Jurine, 1820: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=2723, Revision Date: 9/12/2019, Access Date: 4/22/2024

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.


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Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [4/22/2024].

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