Carcharodorhynchus tenuis Brunet, 1979

Gobert, Stefan, Monnens, Marlies, Eerdekens, Lise, Schockaert, Ernest, Reygel, Patrick & Artois, Tom, 2020, Schizorhynchia Meixner, 1928 (Platyhelminthes, Rhabdocoela) of the Iberian Peninsula, with a description of four new species from Portugal, European Journal of Taxonomy 595, pp. 1-17 : 11

Carcharodorhynchus tenuis Brunet, 1979

Fig. 3 A–D

Material examined

PORTUGAL • 1 whole-mount (photographs of live specimen available); Algarve region , Sagres, eastward of Mareta beach; 37°00′10″ N, 08°56′06″ W; 20 May 2013; B. Tessens leg.; coarse sand and shell gravel, depth 12 m; HU X.1.46 .

Previously known distribution

Bay of Marseille, France ( Brunet 1979).

Remarks

The specimen is eyeless. Live specimens are colourless and transparent. A single, continuous adhesive girdle is present at the caudal body end. A rosulate pharynx is present at about 65%. The proboscis is highly asymmetrical: the ventral tongue measures approximately 44 μm, while the larger dorsal tongue measures 61 μm in length. The proboscis armature consists of rows of small, triangular teeth. On the ventral proboscis tongue, four to six teeth are set in a single row on either side of the tongue, with the teeth increasing in size distally. These teeth have a basal diameter of up to 4 μm and measure up to 3 μm in length. On the dorsal proboscis tongue, the teeth are arranged in multiple rows. In the distal part of the proboscis, the teeth are largest, with a diameter of 1–2 μm and a length of approximately 2 μm. These are more or less set in a single row. In the middle section of the proboscis tongue, the proboscis teeth are small and form a field of 3–4 rows. At the base of the dorsal tongue, the teeth are once again arranged in a single row. In the area connecting the tongues, the teeth form another wider field of about three rows.

Two very long seminal vesicles enter the proximal end of the copulatory bulb. The proximal ends of the seminal vesicles lie on either side of the pharynx. The male copulatory system holds a sclerotised, conical cirrus with a length of 15 μm, armed with very fine spines. In our specimen, the proximal spines have a diameter of 3–4 μm in the proximal region and 11–12 μm in the distal region of the cirrus. The male copulatory bulb connects to the male atrium, which is surrounded by circular to slightly diagonal muscles and leads into the common genital atrium. The common genital opening is situated at about 80%.

A pair of ovaries is situated caudally, near the adhesive belt. No further details of the female reproductive system could be observed.

The arrangement of the proboscis armature differs somewhat from the proboscis armature as described by Brunet (1979). In particular, the fields of spines are wider (four to six rows of spines, instead of just three or four). Carcharodorhynchus isolatus Schilke, 1970 has a very similar organisation of the proboscis teeth. However, rather than two fields of spines, interrupted by a short section in which the spines are in a single row, the spines form a long stretch of three to four continuous rows. Furthermore, C. isolatus has a substantially larger proboscis, even though the size of the proboscis teeth is approximately the same as those reported here. With a length of 15 µm, the cirrus of our Portuguese specimen is slightly longer than what has been described for C. tenuis (9 µm). In addition, Brunet (1979) mentions a tubular shape, while our specimen displays a more conically-shaped cirrus. However, this difference is likely the result of either the flattening of the specimen or the state of contraction of the copulatory bulb (or a combination of both).

Figures

Fig. 3. A–D. Carcharodorhynchus tenuis Brunet, 1979 (HU X.1.46). A–B. Proboscis. C–D. Copulatory bulb. E–H. C. flavidus Brunet, 1967. E–F. Proboscis (HU X.1.49). G–H. Copulatory bulb (HU X.1.48– 49). I–L. C. multidentatus Brunet, 1979 (HU X.1.50). I–J. Proboscis. K–L. Copulatory organ. Scale bars: 20 µm.