Megacyclops viridis
Jurine, 1820
Common Name:
A cyclopoid copepod
Synonyms and Other Names:
Acanthocyclops viridis
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).
Great Lakes 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. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, 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.
Full list of USGS occurrences
Table last updated 5/1/2024
† 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.
Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...
Current research on the environmental impact of Megacyclops viridis in the Great Lakes is inadequate to support proper assessment. Realized:
Megacyclops viridis is an important prey item for various size classes of introduced ruffe (Gymnocephalus cernua) (Ogle et al. 1995). As a large carnivorous copepod, it has been noted to feed on fish larvae and could potentially compete with young fish over sources of food such as oligochaetes and other plankton or larval organisms (Fryer 1957).
There is little or no evidence to support that Megacyclops viridis has significant socio-economic impacts in the Great Lakes.
There is little or no evidence to support that Megacyclops viridis has significant beneficial effects in the Great Lakes.
Potential:
Studies in Eurasia have indicated that M. virdis, like other cyclopoid copepods, could act as a biological control agent of certain mosquito larvae, which has implications for dengue fever control in parts of the world (Blaustein and Margalit 1994, Dieng et al. 2002, Fryer 1957).
Management:
Regulations (pertaining to the Great Lakes)
There are no known regulations for this species. Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Biological
Megacyclops viridis is an important prey item for introduced ruffe (Gymnocephalus cernuus), but the ruffe feeds on a wide variety of benthic organisms, so its feasibility as a biocontrol is unknown (Ogle et al. 1995). Yellow perch (Perca flavescens) and trout perch (Percopsis omiscomaycus) are potential predators of M. viridis (Ogle et al. 1995). Hansen and Jeppesen (1992) found that a 50% reduction of planktivorous fish biomass (roach, Rutilus rutilus, and bream, Abramis brama) affected cyclopoid copepod population directly through reduction in fish predation pressure and changes in biological structure of Lake Væng, Denmark.
Physical
There are no known physical control methods for this species. M. viridis is tolerant to salinity of a wide range, up to 7.9 g L-1 in one study (Wolfram et al. 1999).
Chemical
The Great Lakes and Mississippi River Interbasin Study (GLMRIS 2012) suggests that alteration of water quality using carbon dioxide, ozone, nitrogen, and/or sodium thiosulfate could be effective in preventing upstream and downstream movement of copepods. It should be noted that the effectiveness of these methods is likely significantly diminished against copepod ephippia.
Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.
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 reference list)
Author:
Kipp, R.M., J. Larson, T.H. Makled, and A. Fusaro
Contributing Agencies:
Revision Date:
9/12/2019
Citation for this 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, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatLakes/FactSheet.aspx?Species_ID=2723&Potential=N&Type=0&HUCNumber=DGreatLakes, Revision Date: 9/12/2019, Access Date: 5/1/2024
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.