Salpida
General morphology

The general morphology of salps is illustrated in the sagittal sketches (solitary zooid, aggregate zooid) and Figs. (Cyclosalpa pinnata, Cyclosalpa pinnata 1, Thalia democratica, Thalia democratica 1, Thalia democratica 2), to help identify the structures in the remaining figures, all of which are schematic. Only the structures most important for identifying species have been emphasized; i.e. most of the drawings do not show the oral or cloacal (atrial) muscles precisely, as they are very slender and difficult to place correctly in a sketch of the whole animal.

Identification of salps is based mainly on the arrangement of the body muscles, which have been labelled with Roman numerals in antero-posterior order (e.g., MI means body muscle I) (Cyclosalpa pinnata). The number of fibers per muscle is, in some cases, an important taxonomic character as well. If the muscles have been adequately preserved, this number can be determined easily utilizing a stereoscopic microscope. In the species of Cyclosalpinae (Cyclosalpa pinnata, Cyclosalpa pinnata 1), the morphology of the dorsal tubercle (or opening of the neural gland located beneath the dorsal nervous ganglion) is also taken into account, although this characteristic usually varies with the age of the individuals (Van Soest, 1974a; Esnal et al., in press). The structure of the light organs, as well as characteristics of the attachment organ (or peduncle) of the aggregate zooids, are also meaningful for species identification. In the species of Thalia, the various projections of the test are also important (Thalia democratica, Thalia democratica 1), using the nomenclature suggested by Van Soest (1973a). The arrangement of the stolon (Thalia democratica, Thalia democratica 1; Ihlea racovitzai, fig. E, F; Ihlea magalhanica 1 fig. E, F) in solitary zooids is also used in some cases to differentiate species (Yount, 1954; Madin and Harbison, 1978; Esnal and Daponte, 1990).