Michel Roggo / Brook lamprey (Lampetra planeri) showing sucker, Europe

Michel Roggo / Brook lamprey (Lampetra planeri) Europe

John Cancalosi / Sea Lamprey (Petromyzon marinus) close up of oral disc, from Cayuga Lake, New York, taken in an aquarium

John Cancalosi / Sea Lamprey (Petromyzon marinus) close up of oral disc, from Cayuga Lake, New York, taken in an aquarium

John Cancalosi / Sea Lamprey (Petromyzon marinus) close up of oral disc, from Cayuga Lake, New York, taken in an aquarium

John Cancalosi / Sea Lamprey (Petromyzon marinus) close up of oral disc, from Cayuga Lake, New York, taken in an aquarium

Juan Manuel Borrero / Illustration of Sea lamprey (Petromyzon marinus). Pencil and watercolor painting.

Juan Manuel Borrero / Illustration of diagram of ammocoetes or lamprey larvae (Petromyzontiformes) and Myxine hagfish (Myxine sp). Pencil and watercolor painting.

Michel Roggo / Sea lamprey (Petromyzon marinus) Europe

Michel Roggo / European River lamprey (Lampetra fluviatilis) Larvaes, Sweden, 1998

Michel Roggo / River lamprey (Lampetra fluviatilis) sucker with disk-shaped mouth with horny teeth, Europe, Captive

Michel Roggo / Sea lamprey (Petromyzon marinus) close up of disk-shaped mouth with horny teeth, Europe, Captive

Michel Roggo / European River lamprey (Lampetra fluviatilis) Europe

Michel Roggo / Brook lamprey (Lampetra planeri), Europe

Michel Roggo / Brook lamprey (Lampetra planeri) Europe

Michel Roggo / Brook lamprey (Lampetra planeri) at spawning ground, Glane River, Switzerland, 1990

Paul Hobson / Brook Lamprey (Lampetra planeri) Derbyshire, uk

Paul Hobson / Brook Lamprey (Lampetra planeri) Derbyshire, uk

Willem Kolvoort / Brook lampreys (Lampetra planeri) preparing their spawning place in river, Holland

Willem Kolvoort / Brook lampreys (Lampetra planeri) nesting and preparing to mate in river, Holland

Willem Kolvoort / Brook lamprey adult (Lampetra planeri) Holland. Eyes only exist in the adult phase, with seven gill holes on each side and only one nose hole.

Willem Kolvoort / Brook lampreys (Lampetra planeri) gathering to find a suitable spawning place in river, Holland

Willem Kolvoort / Brook lampreys (Lampetra planeri) preparing their spawning place in river, Holland

Willem Kolvoort / European river lamprey (Lampetra fluviatilis) looking for mating place in brook, Holland

Willem Kolvoort / Close up of Brook lamprey larva mouth (Lampetra planeri) the large upperlip catches the food as detritus out of the waterstream, aquarium set up, Holland

Willem Kolvoort / Geelmolenbeek, brook through woodlands,breeding habitat for Brook lamprey (Lampetra planeri) Holland

Willem Kolvoort / Blind larva of Brook lamprey (Lampetra planeri), uses mouth with large upper lip to catch detritus and sits in the bottom for about 6-7 years, captive in aquarium, Holland

Willem Kolvoort / Split level view of Brook lampreys (Lampetra planeri) underwater in brook preparing a nesting place, Holland

Willem Kolvoort / Brook lampreys (Lampetra planeri) underwater in brook preparing a nesting place, Holland

Willem Kolvoort / Geelmolenbeek, brook through woodlands, the white sandy areas are the preferred mating habitat for Brook lamprey (Lampetra planeri) Holland

Willem Kolvoort / Brook lamprey (Lampetra planeri) underwater in breeding brook, Holland

Willem Kolvoort / Underside view of mouth suction pad of Brook lamprey (Lampetra planeri) captive in aquarium, Holland

Willem Kolvoort / Underside view of mouth suction pad of Brook lamprey (Lampetra planeri) captive in aquarium, Holland

Willem Kolvoort / European river lamprey (Lampetra fluviatilis) male and female pair preparing to mate, Holland

Willem Kolvoort / Underwater view of Brook lampreys (Lampetra planeri) in brook preparing a nesting place, Holland

Willem Kolvoort / Split level view of Geelmolenbeek, brook through woodlands, preferred mating habitat for Brook lamprey (Lampetra planeri) Holland

Willem Kolvoort / Blind larva of Brook lamprey (Lampetra planeri), it lives from detritus and sits in the bottom for about 6-7 years, captive in aquarium, Holland

Willem Kolvoort / Side view of aquarium with blind larva of Brook lamprey (Lampetra planeri), it lives from detritus and sits in the bottom for about 6-7 years, captive, Holland

Willem Kolvoort / European river lamprey (Lampetra fluviatilis) mating, male twists body round female to fertilise eggs which she is spawning, Kauguri Canal, Kemeri NP, Latvia

Willem Kolvoort / European river lamprey {Lampreta fluviatilis} Kaugari canal, Kemeri NP, Latvia. The seven holes behind the eye are the outlets of the gills.

Willem Kolvoort / European river lamprey (Lampetra fluviatilis) female attached by its jaw sucker to a stone in the Kauguri Canal, Kemeri NP, Latvia, during the mating season.

Willem Kolvoort / European river lamprey (Lampetra fluviatilis) male preparing to mate with female which attached by its jaw sucker to stone in the Kauguri Canal, Kemeri NP, Latvia

Doug Perrine / Pacific hagfish {Eptatretus stoutii} captive

Constantinos Petrinos / Crinoid shrimp camouflaged on aquatic plants {Periclimenes commensalis} Sulawesi Indonesia

Joel Sartore / Photo Ark / Gulf hagfish (Eptatretus springeri) head portrait, Gulf Specimen Marine Lab. Captive, occurs in Gulf of Mexico.

Joel Sartore / Photo Ark / Pacific hagfish (Eptatretus stoutii) coiled up, portrait, Gulf Specimen Marine Lab and Aquarium. Captive, occurs in Pacific Ocean.

Joel Sartore / Photo Ark / Two Pacific hagfish (Eptatretus stoutii) coiled up, portrait, Gulf Specimen Marine Lab and Aquarium. Captive, occurs in Pacific Ocean.

Joel Sartore / Photo Ark / Gulf hagfish (Eptatretus springeri) head portrait, Gulf Specimen Marine Lab. Captive, occurs in Gulf of Mexico.

Joel Sartore / Photo Ark / Gulf hagfish (Eptatretus springeri) portrait, Gulf Specimen Marine Lab. Captive, occurs in Gulf of Mexico.

Joel Sartore / Photo Ark / Gulf hagfish (Eptatretus springeri) portrait, Gulf Specimen Marine Lab. Captive, occurs in Gulf of Mexico.