Megacyclops gigas is the largest among the cyclopoid copepod species in Norway. It is most common in small ponds that may be situated above timberline.

Key characteristics

M. gigas is the largest among the cyclopoid copepod species in Norway. Though species within the genus Cyclops may be of nearly the same size (i.e. C. insignis), the body of M. gigas is more robust. P5 (last pair of leg) are very characteristic in Megacyclops sp. M. gigas is distinguished from M. viridis by the length of the inner seta of the furca, which in M. gigas is less than twice as long as the outer one. The inner seta is comparatively larger in M. viridis. The furca of M. gigas is longer than in M. viridis. Its colour is of light yellowish brown with a more or less distinct olivaceus or greenish tinge.

Female: Length 2.2–2.8 mm

Male: Length 2.0–2.5 mm

Ecology and distribution

M. gigas is a common littoral copepod found in about 14 % of the water bodies. It is found in all parts of the country, and occurs from sea level to 1371 m a.s.l., with its highest frequency (>20 %) above 1000 m a.s.l. Though it occurs in water bodies of all sizes, it is most common in ponds with a surface area <0.1 ha. When pH>5, the frequency of water bodies containing M. gigas is relatively constant. Below this value there are few records. The content of electrolytes does not seem to affect the species, which is found with its highest frequency in both ends of the electrolyte gradient.

    Høyde over havet (moh.)|Elevation (m a.s.l.)
    Vitenskapelig navn < 100 100-299 300-499 500-699 700-999 >1000
    13,1 17,6 12,7 7,5 5,7 22,2
    Innsjøareal (da)|Surface area (da)
    Vitenskapelig navn < 0,01 0,01 - 0,09 0,1 - 0,9 1,0 - 9,9 10,0 - 99 100 - 999 > 1000
    20,6 20,9 13,6 14,5 10,4 14 17,4
    Ledningsevne (m S/m)|Conductivity (m S/m)
    Vitenskapelig navn < 1,0 1,0 - 1,4 1,5 - 1,9 2,0 - 2,9 3,0 - 3,9 4,0 - 4,9 5,0 - 6,9 7,0 - 9,9 > 10,0
    18,5 10,2 12,8 9,4 11,1 11,1 11,2 20,4 24,2
    pH
    Vitenskapelig navn < 4,5 4,5 - 4,9 5,0 - 5,4 5,5 - 5,9 6,0 - 6,4 6,5 - 7,0 7,0 - 7,4 > 7,5
    0 6,9 17,7 15,5 14,5 15,1 15 20,6

Look alikes

Megacyclops viridis