Cycloporus papillosus (Sars 1878)

Elongated worms 11 mm long and 6 mm wide. Body shape elongated with light undulating margins and rounded anterior and posterior ends. Dorsal surface with numerous papillae. Colouration orange, yellowish orange or translucent grey with white patches at the mid-dorsal line (Figure 1A, B, C, D). Ventral side smooth and pale. Short inconspicuous marginal tentacles. Sucker located approximately in the middle of the body (Figure 1E). Tentacular eyes scattered over dorsal margin of tentacles (Figure 1A), cerebral eyes in two elongated, anteriorly anastomosing clusters. Plicate cylindrical or tubular pharynx near anterior end, frontally oriented; oral pore posterior to brain. Male and female genital pores clearly separated and posterior to pharynx (Figure 1E). Male copulatory apparatus located posterior to male pore and oriented mainly dorso -ventrally, but also directed frontally (Figure 1E, F). Male system consists of a short, armed (stylet) penis papilla, a true prostatic vesicle with a smooth glandular epithelium, and a well developed, muscularized seminal vesicle. Prostatic vesicle opens directly into penis papilla, and seminal vesicle empties directly into distal end of prostatic vesicle. Vasa deferentia, sometimes very dilated, open proximally through a common duct (common vas deferens) into seminal vesicle. Inconspicuous female system lies posterior to the male pore and is characterized by a short female atrium, female duct (vagina), and characteristic uterine vesicles. Abundant cement glands are located around female pore and distal part of vagina.

In Galicia, three specimens of Cycloporus papillosus were captured from mussels collected on Botrylloides violaceus on the docks of the Yacht Club Ribeira (Ria de Arosa, Galicia, Spain). Depth varied between 0.5 and 1 metres (42°33.7770N, 008°59.2970W; 42°33.7850N, 008°59.3140W; 42°33.7930N, 008°59.3290W). Another specimen (Figure 1B) was collected on a colony of Botryllus schlosseri (Ascidiacea) growing on a rock of the island of Rua (Ria de Arousa, Galicia, Spain), at a depth of 14 metres (42°32.9650N, 008°56.4590W). This is the southernmost European record for Cycloporus papillosus, and the first for the Atlantic coast of the Iberian Peninsula. Other localities from where this polyclad has been reported are: Bergen, Norway (Jensen 1878); Rovigno, Croatia (Vàtova 1928); Susaki near Simoda, Japan (Kato 1937); Porto Praia, Cape Verde (Laidlaw 1906); Plymouth, United Kingdom (Gamble 1893).