About Prostheceraeus vittatus (Montagu, 1815)
Prostheceraeus vittatus (Montagu, 1815) can grow to approximately 50 mm (2 in) in length and 25 mm (1 in) in width. It has an elliptical shape, with a rounded front (anterior) end and a more tapering back (posterior) end. It is flattened from back to belly (dorso-ventrally flattened), with an undulating, wavy body margin that forms a pair of tentacles at the anterior end. These tentacles hold many simple eyes, and additional eyes are located just behind the cerebral organ. The mouth sits on the underside of the body, and the gut divides into many interconnected anastomosing branches that carry nutrients to all areas of the body. A ventral sucker is also present. This flatworm has a distinctive yellowish or cream base color, marked with a central black longitudinal stripe, plus other fainter dark stripes that run parallel to the body margin. It has no body segmentation, and lacks the dorsal processes found on sea slugs. Sea slugs are often confused with this species, but the two are not closely related; Prostheceraeus vittatus is a flatworm, not a mollusc. Prostheceraeus vittatus lives in the temperate northeastern Atlantic Ocean. Its range includes the western coasts of the British Isles, the North Sea, the English Channel, and the western Mediterranean Sea. Beyond the United Kingdom and Ireland, it has also been recorded in Denmark, Norway, and Corsica. It occurs from the intertidal zone down to depths of 20 m (66 ft) or deeper. In the intertidal zone, it hides in crevices, under stones, under seaweed, and among tunicate colonies. As turbellarians, these flatworms appear to glide over substrates, moved by the beating of cilia on their ventral surface. They are carnivorous, feeding on tunicates and other small invertebrates. They are hermaphrodites, and reproduce via copulation with internal fertilisation. They lay small batches of eggs in gelatinous masses, and the eggs develop directly into miniature adult flatworms.
