Whitish (generally) multiple branch structure that tends to develop in a single plane

Compared with other sea rod octocorals, the Knobby Sea Rod is distinguished by its relatively slender branches in relation to their overall diameter when all polyps are extended. Thus called because of the knobs that remain on the branch surface once the polyps have retracted. This is the only visual feature that distinguishes it from the otherwise very similar Warty Sea Rod (q.v.) where retracted polyps look like creviced lumps (hence the warty association).