Uncinorhynchus vorago Willems, Sandberg & Jondelius, 2007, sp. nov.

Uncinorhynchus vorago sp. nov.

(Fig. 4 A–C)

Type locality. Loc. 2.

Type material. One animal studied alive, whole-mounted and designated holotype (SMNH no. 7180). Etymology. Species name refers to the type locality. Vorago (Latin): of watery depths, an abyss, chasm. Description. The live animal was only observed for a short time, both because of its initial preliminary identification as Uncinorhynchus flavidus Karling, 1947, and a high degree of squashing early on. Therefore the exact location of the pharynx and the presence and structure of the organs could not be determined.

The rather slender animal is yellow and lacks eyes. The two proboscis hooks (Fig. 4 A) are 29 µm high (top-bottom measurement), each with two, 51 µm-long basal wings and a curved pointed hook. At the transition between the actual hook and the wings, a very thin, frayed hem is present. The pear-shaped to globular, very muscular prostate vesicle (Fig. 4 C) is situated in the most caudal part, receives sperm from a simple, large and extracapsular seminal vesicle (Fig. 4 C: vs) and is connected to a triangular stylet (Fig. 4 B, 4C: st). The stylet (Fig. 4 B), which has a rather blunt and short distal tip, is 76 µm long and consists of one big plate that is folded into two halves along the convex side of the structure and forms a tube distally. One of the halves shows a lot of wrinkles and folds and the other is rather large and gutter-shaped.

A E A-B, D-E

25 Μm

Diagnosis. Uncinorhynchus vorago sp. nov.: species of Uncinorhynchus with yellow colour and lacking eyes; proboscis hooks ca 29 µm high with basal wings ca. 51 µm long and curved pointed hook; triangular stylet ca. 76 µm long with blunt distal tip, consisting of folded plate which has a tubular part distally.

Discussion. The taxon Uncinorhyncus Karling, 1947 includes 6 species which are all marine, except for U. karlingi Kolasa, 1977, a freshwater species. All species are characterised by the presence of proboscis hooks with two long basal wings and a hook-shaped stylet. The shape of the stylet is very variable, but in known species it always shows a rather long, in some species needle-shaped, in others more dagger-shaped distal tip (Karling 1947, 1952b, 1989; Brunet 1973; Kolasa 1977). Especially the stylet of U. flavidus (Fig. 4 D–E) is superficially similar to that of U. vorago, both in general shape and size (Karling 1947, 1952a, 1989), but in U. vorago, the needle-shaped distal tip is lacking. Uncinorhynchus vorago and U. flavidus both occur in Skagerrak and have a yellow body colour (see Karling 1974).