Ciliophora
Identification of the species

There are only a few reports on planktonic ciliates of the South Atlantic (Ci. table 2a and Ci. table 2b). As these are often outdated or give only species lists, many identifications have to be regarded as doubtful.

Although the diagnoses and descriptions that follow are centered on planktonic species, they also include some benthic or interstitial forms (e.g., Tracheloraphis phoenicopterus), as well as a few normally sessile ones (e.g., Stentor, suctorians). Both types can occur sporadically in plankton samples, especially in nearshore areas, and sessile forms are often found on floating debris and attached to larger plankters, such as copepods.

As aloricate oligotrichs often make up the main portion of planktonic ciliates, a key to common and well-studied marine and freshwater genera is provided. Many of the characters used can be recognized by careful examination of living specimens with differential interference contrast but this requires considerable experience. Thus, additional utilization of silver impregnation is preferred. Keys for other groups or species are inappropriate now because many descriptions of planktonic ciliates are superficial according to modern standards, so correct identification is impossible. But short descriptions of the species recorded in the South Atlantic are given based on life observations and silver impregnation as far as available. If in doubt over an identification, consult the special literature since many new or hitherto unrecorded species are likely to be found in the pelagic realm.

Species names are followed by common synonyms [in square brackets] when available but subsequent incorrect spellings are not listed. Movement of individuals is described, although it alone is not usually sufficient for species identification. Size range (minimum, maximum) is generally from life and thus often an approximation. However, it is valuable because different kinds of fixation lead to variable degrees of shrinkage and distortion (see Ci. 3 Sample preparation and analysis). For each of the species treated one or more references ("Ref.") providing a description and illustrations are given.