HomeInstructionsUse the keyGroupsSpeciesAnatomy
Cyclops scutifer
Phylum Arthropoda
Subphylum Crustacea
Class Maxillopoda
Subclass Copepoda
Order Cyclopoida
Family Cyclopidae
Ecology and Behavior
Distinguishing Characteristics
  • Antennule with 17 segments
  • Ridge present on dorsal side of rami
  • Length of caudal ramus about 4 times the width
  • Tufts of hair present on the inner margins of the cauldal rami
  • 5th leg two segments, distal segment has an apical seta and a subapical spine, which is about equal in length to the segment
  • Minute spinules on distal three segments of antennule
  • Body length approximately 0.7-1.5 mm
Similar Species
    Cyclops scutifer is similar to Cyclops strennus but the fourth thoracic segments of C. scutifer is more expanded and the third mandibular endopod is slightly more than 3 times as long and broad than in C. strennus (1).
Geographic Distribution
    Cyclops scutifer is a freshwater copepod reported in the arctic and northern temperate areas of North America as well as in deep lakes from the USSR, Poland, Norway, Finland, Denmark and most other northern European countries (2).  In North America, populations have been reported in Canada, Alaska, Maine, New Hampshire, Vermont, western Massachusetts, northern New York, northern Pennsylvania and Connecticut (2).
Reported Habitats
    Cyclops scutifer prefer cold, freshwater lakes and often occur at depths greater than 6 meters (2).  Maximum densities occur in spring and early summer when an adequate supply of oxygen is available at temperatures around 10° C.  Populations are forced into the oxygenated upper layers of the lake as the hypolimnion becomes depleted of oxygen (2).  This species can tolerate temperatures up to 15° C (2).
Reproductive Habits
    Males synchronize their swimming patterns with females during mating (3).  After approximately 20 seconds of synchronized swimming, the male makes one large jump to come in contact with the female (3)(4).  The male then grasps the female and transfers paired spermatophores to her urosome, placing it near her gonopore (genital opening).  Shortly after transfer of the spermatophore, the male releases his grasp on the female (3).  Reproduction occurs early in midsummer, and about 45 eggs are produced per adult female (3).
Food and Feeding Behavior
    C. scutifer is an omnivorous species feeding on small cladocerans, rotifers, diatoms and dinoflagellates (5).  C. scutifer is able to detect and swim toward prey based on either the displacement of water during swimming or through acoustic signals (4)(5).
    Cyclops scutifer feed on the same organisms as Mesocyclops edax and Asplanchna priodonta but competition between these species in Mirror Lake (NH, USA) was minimal because of seasonal variability (6).  In Mirror Lake, maximum densities of C. scutifer occurred in spring and early summer, but C. scutifer competed only in December with A. priodonta and in early June with M. edax. The remainder of the year, C. scutifer was deeper in the water column than M. edax (6).
    In New England lakes, C. scutifer had negligible diel vertical migrations; the distribution of this species seems to be based upon temperature and oxygen rather than light (2).  
Seasonal Population Variation
    The C. scutifer population in three Connecticut lakes varied seasonally with maximum densities in the spring and early summer (2).

(1) YEATMAN, H. C.  1944.  American Cyclopoid Copepods of the Viridisvernalis Group, (Including a Description of Cyclops carolinianus n. sp.).  Am. Midl. Nat.  32: 1-90.

(2) ELGMORK, K.  1967.  On the Distribution and Ecology of Cyclops scutifer Sars in New England (Copepoda, Crustacea).  Ecology.  48: 967-971.

(3) STRICKLER, J. R.  1998.  Observing Free-Swimming Copepods Mating.  Phil. Trans. R. Soc. Lond. B.  353: 671-680.

(4) STRICKLER, J. R.  1975.  Intra- and Interspecific Information Flow Among Planktonic Copepods: Receptors.  Verh. Internat. Verein. Limnol.  19: 2951-2958.

(5) STRICKLER, J. R. AND A. K. BAL.  1973.  Setae of the First Antennae of the Copepod Cyclops scutifer (Sars): Their Structure and Importance.  Proc. Natl. Acad. Sci. USA.  70: 2656-2659.

(6) MAKAREWICZ, J. C. AND G. E. LIKENS.  1975.  Niche Analysis of a Zooplankton Community.  Science, New Series.  190: 1000-1003.

Distinguishing Characteristics
Ridge on back, dorsal, side of each caudal ramus.   17 antennule segements   Tufts of hair on inner margin of caudal ramus
Spine on distal segment of fifth leg equal to length of segment   Minute spinules on distal 3 segements of antennule    
Additional Pictures
Quicktime Movies
Barcode: Ribosomal DNA-28S D3 expansion segment