bootlace worm

Juvenile Lineus longissimus range in colour from dark olive-brown to chocolate-brown, while adults range from blackish-brown to black.

Lineus longissimus may have a row of up to twenty deep-set reddish-brown or black eyes on each side of the snout.

Lineus longissimus usually grows to between 5 and 15 meters long and has been known to exceed 30 meters.