The hag, like the lamprey, lacks paired fins and fin rays. Its skeleton is wholly cartilaginous, without bones, its mouth is jawless; and its skin is scaleless. It is easily recognized by its eel-like form; by its single finfold (a fold of skin, not a true fin) running right around the tail and forward on the lower surface of the body with no division into dorsal, caudal, and anal fins; by the single gill pore on each side, just forward of the origin of the ventral finfold; by its lipless mouth, star-shaped in outline when closed; by the single nasal aperture at the tip of the snout; by its peculiar barbels or “tentacles,” two flanking the mouth on either side and four surrounding the nostril; and by the evertible tongue studded with rows of horny rasplike “teeth.” Being blind, it doubtless finds its food by its greatly specialized olfactory apparatus. It feeds chiefly on fish, dead or disabled, though no doubt any other carrion would serve it equally well.
It is best known for its troublesome habit of boring into the body cavities of hooked or gilled fishes, eating out the intestines first and then the meat, and leaving nothing but a bag of skin and bones, inside of which the hag itself is often hauled aboard, or clinging to the sides of a fish it has just attacked. It is only too common in the Gulf of Maine; perhaps it is not absent there from any considerable area of smooth bottom.
From Fishes of the Gulf of Maine by Bigelow and Schroeder (1953) online courtesy of MBL/WHOIhttp://www.gma.org/fogm/Myxine_glutinosa.htm
Al Bezanson
Good Morning Gloucester 