The sea lamprey (Petromyzon marinus) is an ancient aquatic vertebrate defined by its unique mouth structure. Possessing a primitive yet highly specialized feeding apparatus, its parasitic lifestyle has made it a subject of scientific interest and, in some regions, a source of ecological concern. The specific question of its teeth reveals the core of its biology and its ability to thrive in diverse aquatic environments.
Defining the Sea Lamprey
The sea lamprey belongs to the superclass Agnatha, classifying it as a jawless fish and one of the most primitive living vertebrates. Unlike true fish, its skeleton is made of cartilage rather than bone, and it lacks paired fins. It possesses a long, flexible, eel-like body, typically mottled gray-blue to black, with seven distinct gill openings along its head. It is a parasitic species, feeding on the blood and body fluids of other fish during a portion of its life cycle.
The Structure and Arrangement of Dentition
The sea lamprey’s most distinguishing feature is its large, circular oral disc, which is entirely devoid of a bony jaw. The interior of this disc is lined with numerous sharp, backward-pointing teeth arranged in concentric rows. These teeth are made of keratin, a tough, fibrous protein similar to human fingernails. While determining an exact number is difficult because the teeth are continuously shed and replaced, estimates place the count well over 100 in an adult sea lamprey. New teeth are constantly formed beneath the older ones, ensuring the apparatus remains sharp throughout the parasitic feeding stage.
The Lingual Lamina
Beyond the oral disc teeth, the animal possesses a specialized, file-like tongue known as the lingual lamina. This tongue is also heavily armed with keratinous denticles, making the entire dental arrangement the central component of the sea lamprey’s parasitic success.
How the Teeth Function in Feeding
The entire dentition system is engineered for attachment and fluid extraction, not for chewing flesh. The oral disc functions as a powerful suction cup, allowing the lamprey to firmly latch onto the host fish’s skin. The numerous teeth embedded in the disc secure the grip, digging into the host’s flesh to maintain a strong seal against the suction force. Once attached, the toothed tongue begins a piston-like movement, rapidly rasping through the host’s scales and skin. This action creates a hole providing access to the host’s underlying tissues and body fluids. Feeding is further aided by secretions from its buccal glands, which contain an anticoagulant called lamphredin, ensuring a continuous flow of blood.
Ecological Role and Impact
In its native Atlantic Ocean habitat, the sea lamprey is a parasite, and host fish often co-evolve to survive the attacks. However, in non-native environments like the North American Great Lakes, the sea lamprey acts as a devastating predator. It gained access to the upper Great Lakes after shipping canals bypassed natural barriers, leading to a collapse of commercial and sport fisheries in the mid-20th century. The introduced lamprey preyed heavily on commercially valuable species such as lake trout and whitefish, which lacked natural defenses.
A single sea lamprey can destroy up to 40 pounds of fish during its 12 to 18-month feeding period. Ongoing control efforts, including the application of selective pesticides called lampricides in spawning streams, are necessary to suppress the population and protect the multi-billion dollar Great Lakes fishery economy.