• Denticles on the outer margin of the caudal ramus
• Caudal ramus less than five times as long as wide (10)
• 12 segments in the first antenna
• Fifth leg has one distinct segment (10)

E. prionophorus has a hyaline membrane on the distal antennule segments, whereas E. agilis does not .

E. agilis was found in arctic ponds (2), the Finger Lakes (3), Minnesota (5), and in a moorland pond in Wise Een Tarn in Windemere, England (11). E. agilis probably originated in Hawaii (12).

This species is found in the shallow littoral zone in the summer and the deeper profoundal zone during the fall in Minnesota Lakes (6).

E. agilis consumes mostly diatoms and large filamentous algae (4).
E. agilis may enter the brood pouches of Daphnia and prey upon the eggs, causing increased egg mortality (9).

This species reproduces sexually, allowing for early colonization before parthenogenetic species (8). As with all cyclopoids, E. agilis overwinters as an immature copepodite stage in the water column or sediments; enabling the population to out-compete, Cladocera in the early summer (7).

Macrocyclops albidis, a larger cyclopoid copepod, preys on E. agilis (4).

Daphnia pulex can suppress the population growth of E. agilis due to food competition (1).

E. agilis occur in the oxygenated waters usually ascending into the thermocline (region of greatest temperature change) porton of the water column when seasonal stratification causes anoxic conditions in lower waters (5).

E. agilis utilizes the dispersal mechanisms of wind and flooding to rapidly colonize new areas in (8).

(1) PARKER, R.A. 1961. Competition Between Eucyclops agilis and Daphnia pulex . Limnol. Oceanogr.. 6: 299-301.

(2) DODSON, S.L. 1975. Predation Rates of Zooplankton in Arctic Ponds. Limnology and Oceanography. 20: 426-433.

(3) HALL, D.J., AND G.G. WATERMAN,. 1967. Plankton of the Finger Lakes. Limnology and Oceanography. 12: 542-544.

(4) FRYER, G. 1957. The Food of Some Freshwater Cyclopoid Copepods and its Ecological Significance. The Journal of Animal Ecology. 26: 263-286.

(5) TINSON, S., AND J. LAYBOURN-PARRY. 1985. The behavioural responses and tolerance of freshwater benthic cyclopoid copepods to hypoxia and anoxia. Hydrobiologia. 127: 257-263.

(6) COLE, G.A. 1955. An ecological study of the microbenthic fauna of two Minnesota lakes. American Midland Naturalist. 53: 213-230.

(7) HANN, B.J., AND L. ZRUM. 1997. Littoral microcrustaceans (Cladocera, Copepoda) in a prairie coastal wetland: seasonal abundance and community structure. Hydrobiologia. 357: 37 - 52

(8)CÁCERES, C.E.,AND D.A. SOLUK. 2002. Blowing in the wind: a field test of overland dispersal and colonization by aquatic invertebrates. Oecologia. 131: 402 - 408.

(9) HANAZATO, T. AND S.I. DODSON. 1995. Morphological defenses of Daphnia against copepod predation on eggs. Archiv fur Hydrobiologie. 133: 49-59.

(10) HUDSON , P. L., L.T. LESKO, J.W. REID, AND M.A. CHRISCINSKE.  2003.  Cyclopoid copepods of the Laurentian Great Lakes.  Ann Arbor , MI : Great Lakes Science Center Home Page.
  http://www.glsc.usgs.gov/greatlakescopepods/Key.asp?GROUP=Cyclopoid

(11) SMYLY, W.J.P. 1952. The Entomostraca of the Weeds of a Moorland Pond. The Journal of Animal Ecology. 21: 1-11.

(12) http://www.itis.usda.gov/

 Cyclopoid1.mov - Cyclopoid swimming pattern (682 KB)

Eucyclops agilis: Information from the Great Lakes Science Center, USGS