Ceratopera

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 : 18-19

Ceratopera spec.

( Fig. 8 B–C)

Locality. Loc. 2.

Material. One animal observed alive and whole mounted (in bad condition).

Description and remarks. The spindle-shaped animal ( Fig. 8 B) is colourless and has eyes. The pharynx is situated in the first third of the animal and frontal rhabdite-glands ( Fig. 8 B: rg) are well-developed. The copulatory organ is situated in the most caudal part of the animal and consists of a small prostate vesicle associated with a complex stylet ( Fig 8 C). This stylet consists of a pointed, 44 µm-long tube and a surrounding mantle. The tubular stylet carries a plate-like flap, which is wider on one side, near the proximal opening of the stylet. The surrounding mantle, which is 38 m long and 24 m wide proximally, consists of two triangular plates, one on each side of the stylet. One of these plates tapers towards the distal tip of the stylet into a slightly bent and pointed tip. A bursa with two different compartments is situated in the caudal part of the body. One of the compartments is globular in shape ( Fig. 8 B: bu1), and contains coiled-up sperm, whereas the second part of the bursa is sac-like ( Fig. 8 B: bu2).

This species most likely is a member of the taxon Ceratopera Den Hartog, 1964 as the stylet is very similar to that of species included therein (e.g. C. paragracilis Ehlers & Ax, 1974 ; C. gracilis ( Graff, 1882) Den Hartog, 1964 ). This taxon contains 12 species, which are characterised by the shape and size of the stylet and the bursal appendage. The latter is however not observed in the severely damaged specimen from Skagerrak. This, together with the limited amount of observations that could be made on the live individual, hampers the identification of this species. Since the stylet is different from every known member of the taxon, this probably constitutes a new species. However, for reasons explained above, we refrain from formally describing it as such.

Figures

FIGURE 8. Acrumena spec. A, General organisation (from a live individual). Ceratopera spec. B, general organisation (from a live individual). C, stylet (from a whole-mount).