Lamprey

What is a Lamprey?

A lamprey often referred to as a lamprey eel is a parasitic sea creature. Since they prey on the blood of other sea creatures, they are also popular as vampire fishes. A lamprey fish sucks the body fluids along with the blood of other fishes and parasitizes them. They are found in the Atlantic Ocean. These sea creatures have survived at least four major phases of extinction and have not exhibited any genetic evolution for more than 340 million years.

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Image: Lamprey eel 

Classification of Lampreys

Kingdom: Animalia

Class: Hyperoartia

Phylum: Chordata

Order: Petromyzontiformes

Lampreys are fishes that belong to the Petromyzontiformes order of the Petromyzontidae family. These fishes are identified by the scientific name of Petromyzon marinus. A lamprey eel belongs to the Petromyzon genus and there are 8 other genera inclusive of 31 other species in the Petromyzontidae family.

There are about 50 species of lampreys that live on this planet and three major species, namely, river lamprey, brook lamprey, and sea lamprey are found to be prevalent in Europe. These lampreys are found to thrive there for 7 years. The features of each species are discussed below.

River Lamprey

The scientific name of the river lampreys is Lamprey fluviatilis. These lampreys are longer than the brook lampreys and shorter than the sea lampreys. These sea creatures are likely to grow 30 cms to 50 cms in length. The dwarf river lamprey species found in Loch Lomond grows 25 cm in length. The spawning season for the river lampreys extends between May and April and they spawn on pebble substrates. Autumn and Spring are the ideal seasons for the migration of these river lampreys into the freshwater lakes from their coastal habitats. The coasts are preferable feeding grounds for these lampreys whereas they migrate upstream to prepare for spawning. While migrating in autumn, they are still sexually underdeveloped, however, the sea migrants are in spawning condition in Spring.

Brook Lamprey

The scientific name for brook lampreys is Lampetra planeri. These are the smallest British lampreys that can grow 15 cms to 19 cms in length. Brook lampreys are freshwater creatures and they do not feed as adults. The larvae of brook lampreys at times move downstream to find a silty or sandy nursery. During the winter months, the adult lampreys migrate upstream and the spawning season is between April and June. The adult lampreys do not feed and after spawning these lampreys die.

Sea Lamprey

The scientific name for sea lampreys is Petromyzon marinus. This species of lampreys are likely to grow 1m in length. These lampreys feed at the sea for about 18 to 24 months and migrate upstream in spring through early summer. They have a spawning season, extending between May and July.

Physical Description of Lampreys

Sea lampreys resemble eels but are not related by any means. They may show a minimum growth of 5 inches to maximum growth of 40 inches. They have smooth long snake-like slender bodies. They have scaleless skin. The typical characteristic feature of a lamprey is its tapered funnel-like mouth and the sharp teeth lining within. Though a lamprey is referred to as a lamprey fish, it does not have any bony structures like other fishes, but just a cartilaginous skeleton. Also, a lamprey does not have well-defined jaws like fishes, however, it has a unique tapering disk-like mouth. It has an extremely sharp tongue and horn-shaped, sharp teeth lining its mouth.

Habitat and Geographic Range of Lampreys

Sea and brook lampreys dwell in the coastal lands or in the temperate rivers. Lampreys and hagfishes are found in the Atlantic Ocean. Lampreys were located in Lake Ontario for the first time in 1835. These deadly sea creatures could have swum across the other Great Lakes, but for Niagara Falls. The huge falls were initially a natural barrier and restricted the passage of lampreys to the other four Great Lakes. In the early 1900s, the restoration of the Welland Canal established a shipping gateway between the two Great Lakes Erie and Ontario. Thereafter, the canal bypassing Niagara Falls facilitated the passage of sea lampreys to Lake Erie.

Within quite a short time, the sea lampreys were thriving in abundance in the four Great Lakes. These vampire fishes filled up Lake Erie by 1921, Lake Michigan by 1936, Lake Huron by 1937, and by 1938 they thrived abundantly in Lake Superior. The factors due to which the sea lampreys survived in the Great Lakes are as follows.

• Sea lampreys are highly reproductive, that is, one female lamprey can lay nearly 100000 eggs at once.

• The fresh water lakes serve as favourable spawning grounds as well as habitats for the lamprey larvae. 

• The Great Lakes are a repository of host fishes, providing easy access to food for the lampreys.

• There are no potential predators that would lead to any competition for the lampreys in the Great Lakes.

The larvae sea lampreys dwell in the fresh water and they may survive for a time span of 7 years in such habitats. These larvae mostly reside on lake bottoms or muddy areas where they can filter their food on microorganisms like algae and bacteria.

Food Habits of Lampreys

Sea lampreys and brook lampreys feed on algae throughout the year. The amount of larvae ingested by lampreys reduces when they grow into adults. Lampreys are parasitic sea creatures and have a jawless disk-shaped mouth that attaches to the body of a fish. Creatures like the lampreys have a pineal eye that is located at the front of the pineal gland. A lamprey has a cartilaginous mouth that has rows of very sharp horn-shaped teeth lined in its mouth, which latch on to the body of fishes. These lampreys suck out blood along with other body fluids from the body of their prey. When the larvae grow up to full-size adults, lamprey attaches itself to a host fish and draws nutrition from the host fish.

Lamprey Reproduction 

The lampreys move upstream during their spawning season, extending between May and July. Fertilization of eggs occurs outside the body of lampreys. Any area with cobbles or pebbles substrate serves as a good spawning site for all species of lampreys. They build a nest by migrating to their spawning grounds to lay eggs. Mostly lampreys spawn in balls. The brook and river lampreys are likely to spawn in balls comprising 50 individuals, whereas the sea lampreys spawn in fewer numbers.

The lamprey eggs remain upstream till they hatch, and after hatching the larvae are called ammocoetes. These larvae flow downstream with the flow of current when they are hatched, and feed on algae, bacteria, and diatoms. The ammocoetes settle in a nursery in the slow-flowing stream, where there is a well-oxygenated, fine, and soft substrate and they are likely to thrive in such substrates for as long as five or eight years. Once the ammocoetes transform into pre-adults, they are ready to leave the nursery habitats for spawning. From autumn to spring, the sea lampreys, as well as the river lampreys, migrate to the sea for the next cycle of spawning.

Threats and Conservation of Lampreys

Though the sea lampreys multiply at a very fast rate, yet, there are certain threats to these vampire fishes as well. The degradation of fresh water habitats poses a threat to lamprey larvae. All the species of lampreys are threatened due to this fresh water habitat degradation. Since sea and river lampreys migrate up through the rivers for spawning, physical barriers pose threats to their spawning grounds. In-stream structures also have a negative impact on freshwater larvae. River lampreys are exploited in the bait market and fisheries are established to rear them. Also, sea lampreys are used for commercial purposes in certain parts of the European food market. 

Due to the potential threats to the river and sea lampreys, these species are considered priority fish species under the UK Biodiversity Action Plan. The species of dwarf river lampreys is conserved under the Wildlife and Countryside Act 1981, in the Endrick Water Site of Special Scientific Interest.

Though these parasitic sea creatures feed on microorganisms like algae and on the body fluids of other fishes, yet, they are quite edible. When lampreys are consumed they taste somewhat close to that of squids. Hence to avoid extinction, lampreys are being conserved in several parts of the world as they support certain industries.