Abstract | Introduction | Presentation | Diversity | Main marine currents | The different oceanic zones : Summary of the species - Marine currents and other maps | Cosmopolitanism and endemism | Species indicative of continental drift | Species whose localization is difficult to explain | Anthropic mechanisms | Conclusion

Diversity :

After the description of Calanus finmarchicus in 1770 and Temora longicornis (1792), it was only in the middle of the 19 th century that knowledge of planktonic copepods began to grow. By 1900 more than 400 species had been described. This number had doubled by the start of the Great War, but it then grew very slowly until the early forties. 1950 marked a turning point, with 85 species described, and thereafter 10 to 30 new species were described year in year out (66 in 2000 with the revision of Heterorhabdidae by T. Park; 24 in 2003, 17 in 2004 and 21 in 2005). The most recent species are hyperbenthic or comes from caves.

TABLE I - Distribution of species (excluding forms cited as sp. by authors, Saphirella and Tisbe) as a percentage of the various Orders

	Number of species	percent
Calanoida	2022	79.1
other Orders :	534	20.9
Platycopioida	11	2.1
Mormonilloida	4	0.7
Misophrioida	35	6.6
Cyclopoida	270	50.6
Siphonostomatoida	12	2.2
Harpacticoida	31	5.8
Monstrilloida	171	32

Calanoida, of course, dominate overwhelmingly in the pelagic domain, comprising 43 or 44 families (since Calocalanidae and Mecynoceridae are now included with the Paracalanidae and Parkiidae =? Scolecitrichidae; Arctokonstantinidae is re-established; Kyphocalanidae, Rhincalanidae and Rostrocalanidae are new families) and Diaptomidae, Pseudodiaptomidae and Sulcanidae are considered to be families of essentially brackish- or fresh-water forms.

There are 257 marine genera (of which 2 are debatable: Gaidiopsis among Aetideidae and Pseudhaloptilus among Augaptilidae). Gaidius among Aetideidae, and Amallophora among Scolecitrichidae are deleted.

The number of genera in each family is as follows: Scolecitrichidae: 28 (Byrathis has been transferred to Diaixidae; Pseudophaenna has been transferred to Tharybidae; 7 are in lato sensu ); Aetideidae: 27 (or 30 if Gaidiopsis are accepted, along with Pseudotharybis and Valdiviella, both questionable in this family); Epacteriscidae: 19; Arietellidae: 12 (+ 2 ?: Griceus and Rhapidophorus ); Augaptilidae: 11 (if Alrhabdus in this family, and Pseudhaloptilus confirmed) ; Diaixidae: 10; Ridgewayiidae: 10; Spinocalanidae: 10; Phaennidae: 9 (if Talacalanus is confirmed; Xantharus has been transferred to Scolecitrichidae); Calanidae: 8 ; Clausocalanidae: 8; Heterorhabdidae: 8; Pontellidae: 8; Paracalanidae: 7; Acartiidae: 5; Arctokonstantinidae: 5; Pseudocyclopiidae: 5 (of which Frigocalanus , is questionable in this family); Discoidae: 4; Stephidae: 4; Bathypontiidae: 3 (Foxtonia transfered in the Arctokonstantinidae and Damkaeria transfered in the Spinocalanidae); Eucalanidae: 3; Megacalanidae: 3; Metridinidae: 3; Pseudodiaptomidae: 3 (brackish and inshore); Tharybidae: 3 (or more); Centropagidae: 2 (marine genera only); Euchaetidae: 2; Fosshageniidae: 2; Hyperbionychidae: 2; Parapontellidae: 2; Ryocalanidae: 2; Parkiidae: 1; Temoridae: 1 (marine genera only; + 1 Genus brackish: Eurytemora); Boholinidae: 1; Candaciidae: 1; Kyphocalanidae: 1; Lucicutiidae: 1; Mesaiokeratidae: 1; Nullosetigeridae (ex Phyllopodidae): 1; Pseudocyclopidae:1; Rhincalanidae: 1; Rostrocalanidae: 1; Tortanidae 1; Sulcanidae: 1 (brackish).

Families with herbivorous genera that dominate in surface or sub-surface waters are only slightly diversified: Calanidae, Clausocalanidae, Paracalanidae (with the exception of the genus Calocalanus : 50 species).

Families with high generic diversification usually comprise mesopelagic and bathypelagic forms, which does not always imply a high specific diversity (Aetideidae, Augaptilidae, Heterorhabdidae) .

Conversely the Euchaetidae family, which has only 2 genera: Euchaeta and Paraeuchaeta , with a total of 104 species (plus 3 unidentified), shows the highest diversification, linked to their occupying various depths and their carnivorous nutrition.

The genera of Phaennidae are mostly mesobathypelagic (Xanthocalanus being the most diversified with 50 species), or even hyperbenthic, e.g. Phaenna (3 species)

Scolecitrichidae, whose genera (albeit still poorly defined) are also found at great depths, are divided into many species : Scolecitrichella (31 species), Scaphocalanus (32 species).

Lucicutiidae, with a single genus Lucicutia, has 43 species most of which show a remarkably high vertical distribution.

Spinocalanidae have 10 genera (Foxtonia and Sognocalanus being transferred to the re-established family Arctokonstantinidae), all with only a few species (1 to 3 species) with the exception of Mimocalanus (10) and Spinocalanus (29 species + 3 unidentified).

Another mode of progressive radiation is linked to the way certain families occupy the neritic zone, with some genera adapting to brackish conditions: the Acartiidae, and notably their genus Acartia, 56 species (plus 12 questionable ones), illustrate this mode of speciation.

The genera of Pontellidae are either barely diversified, e.g. Ivellopsis (1 species) or Anomalocera (3 species), or on the other hand highly diversified, for example Labidocera (52 species), Pontella (47 species) or Pontellopsis (25 species).

Epacteriscidae with 19 genera in caves.

If we follow the phylogenetic concepts expressed by Ho (1994), we see that the primitive order of the Platycopioida (1 family: Platycopiidae) is one of the least diversified with 4 genera of which 3 have only one species. They are localised in refuges such as submarine caves: Antrisocopia, Nanocopia, or in a habitat which is almost meiobenthic: Sarsicopia, or hyperbenthic: Platycopia with 8 species.

Misophrioida: 3 families (Misophriidae: 7 genera, Palpophriidae: 1; Speleophriidae: 7 genera ), probably still underestimated, are usually hyperbenthic at great depths or in refuges.

Mormonilloida (1 family: Mormonillidae), typically pelagic with a vast geographical distribution, are known only from 2 genera Mormonilla (which has only 1 species) and Neomormonilla.

The Harpacticoida, essentially benthic, have only a few forms that later adapted to pelagic life (28 species distributed among 17 genera in 7 families. Aegisthidae (with 5 genera), Clytemnestridae (with 2 genera), Ectinosomatidae (with 1 pelagic genera), Euterpinidae ( Euterpina : 1 species), Miraciidae ( Distioculus : 1 species, Macrosetella : 1 species, Miracia : 1 species, Oculosetella : 1 species), Thalestridae ( Parathalestris : 1 species), Tisbidae ( Bathyidia : 1 species, Neotisbella : 1 species, Tisbe : 5 species, Volkmannia : 2 species).

Cyclopoida (Gnathostomes stricto sensu ) are only represented in the plankton by 4 families: Oithonidae (with 3 genera: Limnoithona, Dioithona and Oithona), Speleoithonidae (1 genus: Speleoithona: 3 species), Cyclopettidae, and Giselinidae (hyperbenthic species). Only Oithonidae, primarily with the genus Oithona whose forms have conquered brackish waters, show a certain diversification (44 species), probably because of their vast geographical distribution, and their nutritive mode often considered to be carnivorous. Speleoithonidae, with only 3 known species, are found in submarine caves and in relatively brackish waters. Thaumatopsyllidae, with 4 genera (Australopsyllus, Caribeopsyllus, Orientopsyllus, Thaumatopsyllus), parasitic or commensal at the juvenile stage, were included in the Cyclopoida order by Huys & Boxshall (1991, p.154, 193), Boxshall & Halsey (2004) but according to Ho (1994, p.1295) they should be attached to another order, yet to be defined.

Cyclopoida (sensu poecilostomes) of which a large number of families are commensal or parasitic, have 6 families with forms that are strictly planktonic, or even commensal with pelagic organisms: Corycaeidae (2 genera: Corycaeus : 33 species, Farranula : 6 species); Lubbockiidae (7 genera); Oncaeidae (7 genera: Archioncaea : 1 species, Conaea : 4 species, Epicalymma : 6 species , Monothula : 1 species, Oncaea : 69 species, Spinoncaea : 3 species, Triconia : 21 species). The genus Pachos, questionable in this family: 3 species; Paralubbockiidae (1 genus: Paralubbockia : 1 species); Sapphirinidae (3 genera: Copilia : 7 species, Sapphirina : 15 or 20 species, Vettoria : 4 species); Urocopiiidae (1 genus: Urocopia : 2 species); among Clausidiidae the genus " Saphirella " covers juvenile forms (14 forms) of benthic adults (Hemicyclops).

Siphonostomatoida (previously Cyclopoida siphonostomes), essentially parasites, comprise 3 families with free planktonic forms which are however temporary due to their commensalism: Megapontiidae (1 genus: Hyalopontius : 9 species); Pontoeciellidae (Pontoeciella : 1 species) et Rataniidae (1 genus: Ratania : 2 species).

Monstrilloida, with a single family, the Monstrillidae, whose genera should be redefined (6 genera: Australomonstrillopsis, Caromiobenella, Cymbasoma, Monstrilla, Maemonstrilla, Monstrillopsis, plus and with doubt Thaumatohessia), are parasites at the juvenile stage, and are still only known from a limited number of forms (about 123 species).