Utelga heinckei ( Attems, 1897 ) Karling, 1954

Willems, Wim R., Sandberg, Maria I. & Jondelius, Ulf, 2007, First report on Rhabdocoela (Rhabditophora) from deep parts of Skagerrak, with the description of four new species, Zootaxa 1616, pp. 1-21 : 16

Utelga heinckei ( Attems, 1897) Karling, 1954

( Fig. 6 E–F)

Localities. Loc. 2 and Loc. 5.

Known distribution. Northern Atlantic (see Karling 1980 and references therein): west coast of USA, North Sea, Skagerrak, Irish Sea, Irish Atlantic coast.

Material. Two individuals studied alive and whole-mounted.

Description and remarks. In both studied individuals one of the three hooks associated with the male copulatory organ is larger than the two other ones ( Fig. 6 E: 23µm, 11µm, 11µm and Fig. 6 F: 20µm, 11µm, 10µm). The measurements correspond to earlier data (e.g. Karling 1980: 22–36 µm), although the hooks are a bit shorter in the two Skagerrak-specimens. At first sight, the shape of the hooks seems to differ between the two individuals, but when closely examining their construction it is clear that they are all very similar. In both individuals all hooks have a straight gutter-shaped spine-like part and a more plate-like part that can be bent under different angles in respect to the spine-like part. This explains the overall difference in appearance between the hooks of both individuals, but also explains the odd shape of the larger hook in one individual ( Fig. 6 E), where the angle is ± 180º. In both specimens an odd-looking secretion consisting of light-refracting, very coarse grains is present in the prostate vesicle.

Figures

FIGURE 6. Prognathorhynchus dubius A, general organisation (from a live individual). B, proboscis hook (from live individual; freehand drawing). Proxenetes segmentatus. C, bursal appendage (from a whole-mount). D, stylet (from a whole-mount). Utelga heinckei E – F, stylet hooks of two different individuals (from whole mounts).