Flabellina verrucosa

Coryphella verrucosa, is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Flabellinidae. It is found on either side of the northern part of the Atlantic Ocean. The type locality of Coryphella verrucosa is Bergen, Norway. Current thinking is that it is widespread in the North Atlantic Ocean but that specimens found in the North Pacific Ocean are a closely related species. In North America, its range includes the Gulf of St Lawrence and the Gulf of Maine. Animals from British Columbia and Alaska differ significantly in colour pattern and are probably a sibling species, described as Coryphella longicaudata O'Donoghue, 1922. Coryphella pseudoverrucosa has recently been described as a separate species from the NW Pacific. The original description of this species is of an animal with unusually short, rounded cerata, hence the name verrucosa. The name has been extensively used for animals of different appearance, with long cerata, including Coryphella rufibranchialis, the type species of the genus Coryphella. The body of Coryphella verrucosa is translucent white. The tail is elongated and pointed with a mid-dorsal line of opaque white pigment in which there are round translucent spots. This white line may extend along the back amongst the cerata from the tail, breaking up into spots. In different parts of its range this species has differently coloured forms, which may be different species. In some places the digestive gland in the cerata is red while in other locations, cerata with brown digestive gland predominate, though it is known that the colour of the digestive gland in species of Coryphellidae is dependent on diet. There is also considerable variation in the colouring of the tips of the cerata, from narrow broken rings (F. rufibranchialis form) through broad white bands to white almost covering the tips of the cerata in the typical form. The oral tentacles have a broad white stripe on the upper surfaces. The maximum recorded body length is 35 mm or up to 40 mm (1.6 in). This nudibranch is similar in appearance to Microchlamylla gracilis and many other species of Flabellinidae. In Norway this is a common species in depths of 2–10 metres (6 ft 7 in–32 ft 10 in). Minimum recorded depth is 0 m and maximum recorded depth is 183 m. Flabellina verrucosa sensu lato has been reported at depths down to about 300 metres (980 ft) and seems to inhabit both sandy and rocky habitats. Coryphella verrucosa grazes on sessile invertebrates on the sea bed. It also feeds on detritus and plankton. In the United Kingdom, it lives almost exclusively on the oaten pipes hydroid (Tubularia indivisa) whilst the juveniles have a wider diet range.