Rogneda steueri (Steinbock, 1933) Karling, 1953

Artois, Tom J., 2008, Revision of Rogneda Uljanin, 1870 (Rhabditophora, Eukalyptorhynchia, Polycystididae) with the description of seven new species, Zoological Journal of the Linnean Society 153 (1), pp. 1-28 : 6

THE STEUERI -GROUP

The largest of the groups is the steueri -group, with six species: two without pigment ( R. gallica , R. martensi ), two with two dorsal stripes ( R. steueri , R. palula ), one with a reticulate dorsal pigment pattern ( R. reticulata ) and R. cincta ( Fig. 9A ), which has a pigment pattern in between that of R. steueri and R. reticulata . The species of this group all have relatively simple stylets, with A and B each consisting of two simple plates. The pigmented species of this group all have a serrated distal end of plates A1 and A2, which is not the case in R. gallica ( Fig. 8B ) and R. martensi ( Figs 8C , 9D, E ). For R. steueri ( Figs 8F , 9C ) this is difficult to assess, but at least plate A2 seems to have a serrated distal end. R. steueri is characterized by very slender plates A1 and A2. R. palula ( Figs 8D , 9B ) can easily be recognized by the fact that plate B1 distally splits into two parts. The stylets of R. cincta ( Fig. 8A ) and R. reticulata ( Fig. 8E ) resemble each other very closely. There are, however, some clear differences. Plate A1 of R. cincta shows a bifid distal end, with a rectangular and a more pointy part, the latter one I consider a spine (arrow in Fig. 8A ). In R. reticulata the proximal part of plate B2 is elongated and curved towards the distal point of the stylet (arrow in Fig. 8E ), which is not the case in R. cincta . This feature is very conspicuous, even on living specimens and at lower magnification. Together with the differences in pigmentation, these features make it very easy to distinguish the two species. R. martensi and R. gallica , both unpigmented, can easily be distinguished from each other by the differences found in stylet A, which has a very broad and square proximal part in R. martensi .

Figures

Figure 8. Stylets of the representatives of the steueri-group. A, R. cincta (from the holotype). B, R. gallica (from a specimen from Marseilles). C, R. martensi sp. nov. (from the holotype). D, R. palula (from the lectotype). E, R. reticulata (from the holotype). F. R. steueri (from the neotype). Stylet A is indicated by an A, stylet B by a B. For each stylet plate 1 is indicated by a 1, plate 2 by a 2. Arrows: see text. Scale bar = 25 Mm.

Figure 9. Habitus and stylets of representatives of the steueri-group. A, habitus of R. cincta (from the holotype). B, stylets of R. palula (from the lectotype). C, stylets of R. steueri (from the neotype). D, stylet B of R. martensi sp. nov. (from the holotype). E, stylet A of R. martensi sp. nov. (from the holotype). Arrows: see text. Scale bars = A = 50 Mm; B–E = 20 Mm.