Ctenophora
Geographic distribution
Major works on ctenophore taxonomy were usually focused on restricted geographic areas. As an example, Chun (1880) described the ctenophores from the Gulf of Naples, Italy; and Mayer (1912) presented an important contribution for the Northwestern Atlantic waters. Moser (1910) produced the first world-wide distributional study, but the South Atlantic remained with only a few species-specific records. Recently, Hernández-Nicaise and Franc (1993) published an updated geographic distribution of Ctenophora, and it is clear that a very noticeable gap still remains in the South Atlantic.
The data in the following figures are derived from a compilation of all literature records, and from personal research records. This is an initial attempt to assemble all the available information.
Order Cydippida map
Order Cydippida map 2
Order Cydippida map 3
Order Lobata map
Order Lobata map 2
Order Lobata map 3
Order Cestida map
Order Beroida map
As pointed out above, the distributional patterns presented here apply mainly to coastal ctenophores. Oceanic ones are still poorly known and special techniques are necessary for their study. Because of the extreme scarcity of ctenophore studies based on submarine surveys, the biogeographic data summarized in the figures of the Georaphic distribution had to draw heavily on reports based on plankton nets. Most of the data are based on personal observation and shipboard identifications following the procedures suggested by O'Sullivan (1986) (see Methods).
The distributional ranges presented include some records from equatorial waters of the Northern Hemisphere; they are included because of the high probability of finding some of these organisms in tropical waters of the Southern Atlantic.
In spite of the widespread distribution of most of the species, which occur in several oceans, the geographic ranges of neritic ctenophores in Southwestern Atlantic Ocean fit well with local biogeographic schemes proposed in the literature (Balech, 1954; Boltovskoy, 1970; Dadon and Boltovskoy, 1982). Warm water species off southern South America include Cestum veneris, Lampea pancerina, Mnemiopsis maccradyi and Beroe ovata. They occur from southern Brazil, Uruguay, and Buenos Aires province (Argentina) down to 42°S. Cold water forms are represented by Callianira antarctica, Pleurobrachia pileus, Mertensia sp., Mnemiopsis leidyi and Beroe cucumis. They occur from 50-55°S to 34-35°S, associated with the subantarctic waters of Malvinas (=Falkland) Current.
The wide shelf off Argentina and the presence of semi-permanent hydrographic features like the Río de la Plata front (freshwater outflow), the north-Patagonian fronts (tidal) (Brandhorst and Castello, 1971; Carreto et al., 1986; Glorioso, 1987; Guerrero et al., 1997), and coastal semi-enclosed areas (Bahía Blanca) (Mianzan and Sabatini, 1985; Mianzan, 1986b), generate especially adequate conditions for the development of important populations of coastal ctenophores, in particular of the genus Mnemiopsis. Members of this group preserve very poorly in net plankton samples (Mianzan et al., 1996), and because of this limitation information on their distribution, and particularly their abundance, is very scarce in the area, even though they are one of the most representative and abundant ctenophores in coastal southwestern Atlantic waters. Present knowledge of ctenophores off South Africa is insufficient for drawing a general pattern.
Vertical profiles are of course scarce for south Atlantic ctenophores. Gibbons (pers. comm., 1996) is currently working on Pleurobrachia pileus, and has found greatest densities during the night in St. Helena Bay (South Africa). Mianzan (unpublished data) observed diel migratory movement of Mnemiopsis leidyi in the north patagonian front (42°S) from 70 m to the surface.