Comoplana agilis (Lang, 1884) Faubel, 1983

Fig. 14

Stylochoplana agilis Lang, 1884 .

Material examined.

• MNHNC MB 16-000125, Station 4, 8 December 2018, 8 mm long ; • MNHNC MB 16-000126, Station 8, 16 May 2018, 4 mm long ; • MNHNC MB 16-000127, Station 8, 17 May 2018, 3 mm long ; • MNCN 4.01/3631 to 3633, Station 11, 28 October 2015, 4 mm long, sagittally sectioned into 3 slides ; • MNCN 4.01/4085, Station 11, 28 October 2015, 4 mm long; and • MNCN 4.01/34634 to 3635, Station 11, 29 October 2015, 6 mm long, sagittally sectioned into 2 slides. All of the measurements from the description refer to this specimen ; • MNCN 4.01/4086, Station 11, 19 June 2018, 3 mm long ; • MNCN 4.01/4087, Station 11, 19 June 2018, 3 mm long .

Description.

small Stylochoplanidae, with lengths varying between 3 mm and 8 mm (4.33 ± 1.66 mm). Body shape elongated much wider in the anterior region and at the blunt posterior end (Fig. 14 A). Dorsal colour differs from dark brown to dark green, with white or cream spots along the central longitudinal area. Conspicuous, cylindrical tentacles located at the anterior end to the beginning of body narrowing. Tentacular eyes (approximately 6 eyes per cluster) inside the tentacles and cerebral eyes (16 eyes per cluster) around the base of the tentacles. (Fig. 14 B). Pharynx ruffled, located more or less central. Oral pore situated in the posterior part of the pharynx. Genital pores joining in a common atrium (Fig. 14 C – E).

Reproductive system.

Male copulatory system with true seminal vesicle, interpolated prostatic vesicle, and conical penis papilla (Fig. 14 C – E). Vas deferens run ventrally and enter proximally into the seminal vesicle through a common duct. Seminal vesicle voluminous (0.12 mm long and 0.23 mm wide), kidney-shaped, and connected proximally to the prostatic vesicle. A narrow ejaculatory duct runs from the seminal vesicle to the lumen of the prostatic vesicle (Fig. 14 D). Prostatic vesicle more or less rounded and well-developed (0.2 mm long and 0.28 mm wide), with a thick muscular wall (0.04 mm) pierced by extravesicular glands. Epithelial lining of the prostatic vesicle smooth. Penis papilla 0.2 mm long, with a sinuous trajectory to the deep and ciliated common atrium.

Female system with a narrow external and internal vagina, Lang’s vesicle present (Fig. 14 D). External vagina runs dorsally and turns backwards, continuing to the internal vagina, which receives the common oviduct ventrally. Lang’s vesicle large, rounded (0.15 mm long and 0.1 mm wide), and lies on the ventral side of the body (Fig. 14 C – E).

Biology.

Due to its small size and colouration, this species is very cryptic on substrates such as stones or sand. The specimens studied were mainly found on algae such as Halopteris scoparia, Dictyota dichotoma (Ochrophyta), and Ellisolandia elongata (Rodophyta) .

Distribution.

Widely known from the Mediterranean, this species was reported in Naples, Italy (Lang 1884), the coasts of Catalonia (Novell 2001), and the Atlantic coasts of Europe, such as Galicia (Aguado et al. 2017), the North Sea (Karez 1991; Harms 1993), and the British coasts (Howson and Picton 1997). This is the first report of this species in Portugal and Andalusia.