The trunk of dark-blue satin tints is covered with ciliated epithelium, which produces a special matter called bonellin.
Nowadays, there are attempts on receiving a new type of antibiotics out of this toxic chlorophyll-like pigment.
Besides, bonellin has a huge significance in worm's reproduction chain. Eggs being hatched on the female's trunk and exposed to the influence of the bonellin are alighted only by self-unreliant males, who descent along the trunk and penetrate into the mate's body.
Female individuals would grow out of eggs and lavrae developed on the ground, without coming into contact with bonellin.