Belongs within: Cyclopidae.
Cyclops is a cosmopolitan genus of freshwater copepods characterised by well-defined, angular epimeres on the anterior segments of the body, giving the sides a more or less jagged appearance, and a rudimentary last pair of legs (Sars 1913a). Representatives include the Holarctic species C. strenuus which differs from many of its congeners in being generally found swimming close to the surface of the water; it has the cephalic segment narrowly rounded in front and the last two trunk segments laterally produced. Cylops lacustris is another limnetic species that is transversely truncate at the front of the cephalic segment and has trunk segments little produced. Cyclops abyssorum, in contrast, is only found in the deepest parts of lakes close to the sediment surface (Sars 1913a).
Characters (from Sars 1913a): Anterior division of body moderately tumid, generally more tapered behind than in front; lateral parts of three anterior trunk segments well defined, sub-angular behind; last trunk segment more or less produced laterally. Tail slender and attenuated, genital segment in female more or less dilated in front. Anterior antennae of varying length, more generally composed of 17 well defined joints, though in some cases, by concrescence, their number may be considerably reduced; those in male strongly hinged, with terminal section distinctly biarticulate. Posterior antennae with all 4 joints well defined, the 1st carrying at the end posteriorly a long ciliated seta. Rudimentary palp of mandibles carrying 2 very long and densely plumose setae accompanied by a short bristle. Maxillary palp scarcely extending beyond masticatory lobe, provided outside near base with 4 ciliated setae, 3 of which issue from a slight expansion of the margin. Anterior maxillipeds moderately strong, with 1st basal joint generally subdivided in the middle, provided anteriorly with a small rounded lobe carrying 2 plumose setae; digitiform lobe issuing from end of this joint anteriorly comparatively small, with none of the setae unguiform. Posterior maxillipeds much more slender, composed of 4 well-defined joints. Natatory legs with both rami generally 3-articulate, though in some cases, by an imperfect separation of the 2 outer joints, one or other of them, or all, may be only biarticulate; inner ramus of 4th pair with 2 apical spines. Last pair of legs very small, generally not extended laterally, composed of 2 joints, the proximal of which in some cases may be coalesced with the corresponding segment, distal joint not expanded, and carrying a slender apical seta and a short lateral spine. Seminal receptacle in female of comparatively simple structure, being generally transversely oval in shape.
<==Cyclops Müller 1776BR05
|--C. abyssicolaS13b
|--C. abyssorum Sars 1863E75 [=C. strenuus abyssorumE75; incl. C. strenuus var. tenuipesS13b]
| |--C. a. abyssorumE75
| |--C. a. apenninae Lindberg 1956E75
| |--C. a. bodanus Kiefer 1954 [=C. rubens bodanus, C. strenuus bodanus]E75
| |--C. a. bohemicus (Sramek-Husek 1937)E75
| |--C. a. carinthicus Lindberg 1955E75
| |--C. a. corsicanus (Lindberg 1955) [=C. rubens corsicanus]E75
| |--C. a. divergens Lindberg 1936E75
| |--C. a. divulsus Lindberg 1956E75
| |--C. a. gracilipes (Sars 1903)E75 [=C. strenuus var. gracilipesS13]
| |--C. a. laevis (Losito 1902)E75
| |--C. a. larianus (Stella 1934)E75
| |--C. a. maiorus Lindberg 1957 [incl. C. abyssorum f. resiae Stella 1934]E75
| |--C. a. mauritaniae (Lindberg 1950)E75
| |--C. a. medianus (Lindberg 1949)E75
| |--C. a. novarensis Einsle 1968E75
| |--C. a. paternonis Lindberg 1956 [=C. rubens paternonis]E75
| |--C. a. prealpinus (Kiefer 1939)E75
| |--C. a. sevani (Mechkova 1947)E75
| |--C. a. sibiricus (Lindberg 1949) [=C. rubens sibiricus]E75
| |--C. a. tatricus (Kozminski 1927) [incl. C. tatricus tovelanus (Baldi 1941)]E75
| `--C. a. vranae (Kozminski 1927)E75
|--C. arnaudiS13b
|--C. attenuatusS13b
|--C. bicolorS13b
|--C. bisetosusS13b
|--C. bohater Kozminski 1933E75
|--C. caeruleus [=Monoculus caeruleus]L02
|--C. capillatusS13b
|--C. captivus [=Monoculus captivus]L02
|--C. chelifer [=Monoculus chelifer]L02
|--C. claviger [=Monoculus claviger]L02
|--C. columbianus Lindberg 1956E75
|--C. crassicaudisS13b
|--C. cunningtoniS13b
|--C. curticornisL02
|--C. dengizica [=C. diaphanus var. dengizica]S13b
|--C. diaphanusS13b [incl. Monoculus minutusL02, C. minutusS13b, C. nanusS13b]
|--C. furcifer Claus 1857E75
| |--C. f. furciferE75
| |--C. f. borealisE75
| `--C. f. caspicusE75
|--C. gigas [incl. C. ingens]S13b
|--C. hutchinsoni Kiefer 1936E75
|--C. insignis Claus 1857E75
|--C. kolensis Lilljeborg 1901E75
|--C. lacinulatusL02
|--C. lacustris Sars 1863E75
|--C. ladakanus Kiefer 1936E75
|--C. languidusS13b
|--C. longicornis [=Monoculus longicornis; incl. C. finmarchius]L02
|--C. lucidulus [incl. C. elongatus, C. parcus, C. vernalis]S13b
|--C. minuticornisL02
|--C. ochridanus Kiefer 1932E75
|--C. pachycomusS13b
|--C. pictusS18
|--C. pulchellus [incl. C. bicuspidatus, C. helgolandicus, C. lubbocki, C. odessanus]S13b
|--C. robustus [incl. C. brevispinosus]S13b
|--C. scmirnovi Rylov 1948E75
|--C. scutifer Sars 1863E75
| |--C. s. scutiferE75
| |--C. s. laurenticus (Lindberg 1956)E75
| |--C. s. scandinavicus (Lindberg 1957)E75
| `--C. s. wigrensis Kozminski 1927E75
|--C. strenuus Fischer 1851E75 (see below for synonymy)
| |--C. s. strenuusE75
| `--C. s. landei Kozminski 1933E75
|--C. thomasiS13b [=C. bicuspidatus thomasiK-M02]
|--C. varicans [incl. C. orientalis, C. rubellus]S13b
|--C. vicinus Uljanin 1875 [incl. C. v. var. glacialis]E75
| |--C. v. vicinusE75
| |--C. v. brevicornisE75
| |--C. v. kikuchiiE75
| `--C. v. lobosusE75
`--C. vulgaris [incl. C. viridis var. americana, Monoculus quadricornis viridis, C. viridis]S13b
Cyclops strenuus Fischer 1851E75 [incl. C. brevicaudatusS13a, C. clausiS13a, Monoculus quadricornis Linnaeus 1758L58, C. quadricornisS13a, M. quadricornis rubensS13a, C. rubensL02]
*Type species of generic name indicated
References
[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.
[E75] Einsle, U. 1975. Revision der Gattuung Cyclops s. str. speziell der abyssorum-Gruppe. Memorie dell’Istituto Italiano di Idrobiologia 32: 57–219.
[K-M02] Klein-MacPhee, G. 2002. Temperate basses. Family Moronidae. In: Collette, B. B., & G. Klein-MacPhee (eds) Bigelow and Schroeder’s Fishes of the Gulf of Maine 3rd ed. pp. 374–389. Smithsonian Institute Press: Washington.
[L02] Latreille, P. A. 1802b. Histoire Naturelle, générale et particulière des crustacés et des insectes vol. 4. Familles naturelles des genres. F. Dufart: Paris.
[L58] Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Laurentii Salvii: Holmiae.
[S13a] Sars, G. O. 1913a. An Account of the Crustacea of Norway with short descriptions and figures of all the species vol. 6. Copepoda. Cyclopoida pts 1–2. Oithonidae, Cyclopinidae, Cyclopidae (part). Bergen Museum: Bergen.
[S13b] Sars, G. O. 1913b. An Account of the Crustacea of Norway with short descriptions and figures of all the species vol. 6. Copepoda. Cyclopoida pts 3–4. Cyclopidae (continued). Bergen Museum: Bergen.
[S18] Sars, G. O. 1918. An Account of the Crustacea of Norway with short descriptions and figures of all the species vol. 6. Copepoda. Cyclopoida pts 13–14. Lichomolgidae (concluded), Oncaeidae, Corycaeidae, Ergasilidae, Clausiidae, Eunicicolidae, supplement. Bergen Museum: Bergen.