Facelina bostoniensis

(Couthouy, 1838)

This is one of the largest British aeolids, reaching 55 mm in length. The body is translucent white in colour, with a rosy pink area around the mouth (F. bostoniensis-drawing). The long, mobile oral tentacles can equal half the total body-length. The tips of the oral and rhinophoral tentacles are covered with opaque white pigment. The digestive gland lobes vary in colour from pale brown to dark chocolate brown. Each ceras exhibits subterminally a shield-shaped patch of opaque white surface pigment. Contrary to the related Facelina coronata, there is rarely any trace of iridescent blue surface pigment over the head. Moreover, the whole aspect of the body is broader in F. bostoniensis.

The diet consists of the hydroids Tubularia larynx, T. indivisa and Clava multicornis.

This species has been recorded from shallow sublittoral localities all around the British Isles (Distr. F. bostoniensis). It is the only amphi-atlantic species of Facelina. Furthermore, it has an extended range in European waters, from southern Norway to the Iberian Peninsula and the western Mediterranean Sea.