Rogneda hibernica (Southern, 1936) 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 HIBERNICA -GROUP

This is a morphologically homogeneous group, containing four species without dorsal subepidermal pigment stripes: R. hibernica ( Figs 5A , 7A ), R. licyae ( Figs 5C , 7C ), R. verveckeni ( Fig. 5D ) and R. vangronsveldi ( Figs 5B , 7B ) (the last species is coloured brownish by a parenchymal pigment and has some dorsal subepidermal pigment at the level of the eyes). Stylet A of these species consists of a relatively simple plate A1, and a plate A2 that is very long and narrow and distally splits into two sharp ends (the shortest of which is considered a spine, indicated with an arrow in Fig. 5A–D ). In R. hibernica , R. vangronsveldi and R. verveckeni plate A1 evenly tapers towards a pointed distal end, whereas in R. licyae it suddenly narrows and is arrowhead-shaped distally (indicated with a dashed arrow in Fig. 5C ). Plate A2 and its spine in R. hibernica , R. vangronsveldi and R. verveckeni are very slender. The spine is much shorter in R. hibernica (as compared with the length of plate A2) than it is in R. vangronsveldi and R. verveckeni . Plate A 1 in R. verveckeni is relatively longer than in R. vangronsveldi , with a longer proximal part, and has a serrated distal rim, which was not observed in any of the other three species. Plate A2 and the spine are much more sturdy in R. licyae . The construction of stylet B is also very typical for the members of this group, consisting of a plate B1 that is distally split and a plate B2 that is a simple rectangular plate with a serrated distal rim. This stylet is very similar in R. vangronsveldi and R. licyae . In these two species, plate B1 has a short proximal part and its distal part is split into a rectangular part with a serrated rim and a hook-shaped part, which I refer to as a spine (this is also the case in R. verveckeni ; see further below). Plate B2 of both species is rather straight and broad, even slightly broader distally than proximally. Stylet B differs in the two species in that the proximal part of plate B1 is much broader in R. vangronsveldi . Plate B1 of R. hibernica and R. verveckeni is longer than in the other two species and has a relatively longer proximal part. It is distally split into two parts: a broad and a narrow rectangular part, both with a serrated distal rim, in R. hibernica (the most narrow considered a spine); and a very narrow rectangular part with a serrated distal rim and a hook-shaped part (the spine) in R. verveckeni . R. hibernica therefore is the only species within the hibernica -group that has the distal ends of both parts of plate B1 blunt and serrated.

Therefore, the evidence for sister group relationships within this group is somewhat contradictory. With regard to stylet A, R. hibernica from the North Sea, R. verveckeni from the Atlantic coast of Spain and R. vangronsveldi from the Mediterranean most resemble each other, whereas the detailed morphology of the stylet B suggests a close relationship between the two Mediterranean species R. vangronsveldi and R. licyae . R. verveckeni has a stylet B with a somewhat intermediate morphology between this of R. hibernica on the one hand and R. vangronsveldi / R. lyciae on the other.

Figures

Figure 5. Stylets of the representatives of the hibernica-group. A, R. hibernica (from the neotype). B, R. vangronsveldi sp. nov. (from the holotype). C, R. licyae sp. nov. (from the holotype). D, R. verveckeni sp. nov. (from the holotype). 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. Scale bar = 50 Mm. Arrows: see text.

Figure 7. Stylets of the representatives of the hibernica-group and the habitus and stylet of R. schaereri sp. nov. A, R. hibernica (from the neotype). B, R. vangronsveldi sp. nov. (from the holotype). C, R. licyae sp. nov. (from the holotype). D, E, R. schaereri sp. nov. [D, habitus; E, stylets (both from the holotype)]. Scale bars = A–C, E = 20 Mm; D = 100 Mm.