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

Species whose localization is difficult to explain :

Certain species have been seen in very widely separated zones without any obvious explanation. In some cases, the authors have argued that this is due to erroneous identification or belated synonymy. For want of a minimum amount of information about the species cited in inventories, it is usually impossible to judge the validity of such identification. This explains why some species cited by C. B. Wilson (1950) in the Pacific are sometimes subject to caution, for example Scolecithricella lobata (Sars, 1920), generally found in the NE Atlantic and the western Mediterranean. Other forms cited were not properly described, as in the case of Candacia guinensis (Chasavar-Archad & Razouls, 1982). 61 other species have never been cited since their original description in 1911, but that of course does not constitute proof that they do not exist. In other cases, however, similar "absurd" localisations are confirmed, as for Paraeuchaeta altibula (Park, 1995, p.53) observed solely in central Japan and off SW Ireland, P. parabbreviata (Park, 1995, p.64) from the Tasman Sea and SW Ireland, P. sesquipedalis (Park, 1995, p.69) off California and in the SE Atlantic (off St Helena). Other cases are problematic, such as Corycaeus affinis reported off Japan and in the Strait of Georgia, off Friday Harbor, and by Stander & De Decker (1969, p.29, 38) off Namibia. Labidocera brunescens, a Mediterranean form, has been reported North of the Azores (Sars, 1925, p.354) but also by Dakin & Colefax (1933, p.206) in the coastal waters of New South Wales ( SE Australia ). Augaptilina scopifera described in the Bay of Biscay by Sars (1925, p.309) has since then only been reported by Séguin (1966 a, p. 1348) in the Cap Verde Islands and by Björnberg (1973, p.348) in Chile. Paraeuchaeta birostrata from the North Pacific was noted by Yamanaka (1976, p.170, 193) in Drake Passage, but this localisation was not validated by Park (1995, p.55). P. californica, considered by Park (1995, p.54) to be endemic to the California-Oregon coast was noted by Yamanaka (1976, p.170) in Chile. P. confusa reported by Park (1995, p.56) in Sino-Japanese waters and the Caribbean was reported by Yamanaka (1976, p.170, 193) in Chile and as far south as Drake Passage. P. malayensis, an exclusively equatorial Indo-Pacific form for Park (1995, p.36) was also reported off Miami by Owre & Foyo (1964, p.343; 1967, p.53) and off Barbados Is. by Sander & Moore (1978, p.232), in Chile down to Drake Passage by Yamanaka (1976, p.171, 193) and off south-east Africa by De Decker & Mombeck (1964, p.13). Metridia gurjanovae is described in the south Bering Sea (Brodsky, 1950 (1967), p.301), at "P" Station in the NE Pacific (Vaupel Klein, 1970, p.34), off Mauritania (Vives, 1982, p.293) and in north and south Chile (Björnberg, 1973, p.337, 387). Pseudochirella palliata, described from the Azores (Sars, 1925, p.92) was reported in the Kuril Trench (Markhaseva, 1989, p.42, 57; 1996, p.285; Markhaseva & Razzhivin, 1992 (1993), p.612). Scaphocalanus bogorovi, described from the Kuril Trench (Brodsky, 1955 a, p.193), has been reported in the western Indian Ocean (Grice & Hulsemann, 1967, p.16, 26) and in the NE Atlantic (Grice & Hulsemann, 1965, p.224, 239), the abyssopelagic character of this species should be noted (a relict from the primitive ocean?). Scaphocalanus insignis described from the NW Pacific (Brodsky, 1950 (1967), p.255), was noted in the Canaries (Vives, 1982, p.292), but synonymy with S. longifurca is suspected. The most surprising localisation is that of Chiridiella brachydactyla described from two females found in the Azores by Sars (1925, p.52) and a male found in Japan (Sagami) by Tanaka (1957 a), however Markhaseva (1996, p.92) does not accept that the male belongs to this species. The female of Scaphocalanus angulifrons was described from the Atlantic (off Lisbon ) by Sars (1925, p.170) and the male from the Philippines by C.B. Wilson (1950, p.325) but confirmed by the presence of females in the same haul. Recently Guangshan & Qian Honglin (1997) described a female in equatorial eastern Pacific ( Arietellus unisetosus ) identical to the female form described by Ohtsuka et al. (1994) from the Canaries as Arietellus sp.

The genus Ryocalanus is represented by six species: R. infelix from Japan (Tanaka, 1956 c, p.404), R. spinifrons from Sagami Bay (Shimode, Toda & Kikuchi,2000) and R. admirabilis from Mauritania (Andronov, 1992, p.140), both on the continental shelf, R. asymmetricus, R. bicornis, R. bowmani (Markhaseva & Ferrari, 1996) deeper off Clipperton.