Rolando, 1821

Description:
Body up to 150 mm long, green and covered with papillae. Proboscis long, extensible to over 1 m, bifid (Bonellia proboscis). Coelom with one nephridium usually on the right side. Anal vesicles saclike, with branches that end in ciliated funnels. Animals with sexual dimorphism, with dwarf males nearly 2 mm long, lacking chaetae, ciliated all over and living inside the female (B. viridis-male). Initially attached to the female proboscis, later within the pharynx and eventually inside the nephridium.
Sex is not determined until after the young settle. A young individual that settles alone on unoccupied substratum almost always grows into a female. An individual that settles in a territory already occupied by mature females, attaches to the proboscis and develops into a male. Fertilization of the gametes is internal.

Habitat:
In rock crevices or under stones, mostly at great depths, but also in shallow water, gathering its diet of algal cells with its long proboscis. The skin is toxic and gives some protection against predators.

Distribution:
Very rare off Norway and Ireland, but common in shallow water of the Mediterranean.