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Lamprey

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Lampreys are a unique group of jawless fish belonging to the order Petromyzontiformes.

Petromyzon marinus
Petromyzon marinus

While they are often mistakenly called lamprey eels, they are actually part of a group called Cyclostomi. This superclass includes lampreys and hagfish, which are the only other living jawless fish.

Petromyzontiformes phylogeny
Petromyzontiformes phylogeny

Lampreys are considered one of the most basal groups of vertebrates. This means they represent a very early branch of the vertebrate family tree. They are distinct from jawed vertebrates because they lack a traditional jaw structure. Instead, they possess a specialized mouth designed for suction and feeding.

The life of a lamprey involves a complex transformation.

Lamprey larva labelled
Lamprey larva labelled

Most lampreys spend the majority of their lives in a juvenile stage called the ammocoete stage. These larvae live in soft sediment like silt or mud. They function as filter feeders, collecting algae, micro-organisms, and detritus from the water. This stage can last for up to eight years in some species. Eventually, the lamprey undergoes metamorphosis, a process that lasts between three and four months. During metamorphosis, the lamprey does not eat any food. After this change, the animal becomes an adult with a completely different lifestyle and anatomy.

Adult lampreys exhibit several specialized anatomical features.

Lamprey anatomy
Lamprey anatomy

They have elongated, scaleless bodies and lack paired fins. One of their most striking features is the buccal cavity, or mouth area. This area allows the lamprey to attach to surfaces or prey using suction. Inside the mouth, they have a piston-like tongue equipped with three horny plates called laminae. They use these plates to scrape through tissue to reach blood and body fluids. Their teeth are made of keratin and proteins. These teeth have a hollow core, which allows new teeth to grow underneath the old ones.

Lamprey Anatomy (50693755972)
Lamprey Anatomy (50693755972)

The sensory systems of lampreys are also quite remarkable. Most lampreys are described as the only living vertebrates with four eyes. They have one pair of regular eyes and two extra eyes called parietal eyes. These include a pineal eye and a parapineal organ. The pineal eye is a photosensitive organ that helps regulate melatonin production by capturing light signals. Furthermore, different families of lampreys have different levels of visual complexity. For example, the family Geotriidae possesses five different types of photoreceptors.

The history of the lamprey spans hundreds of millions of years.

Yanliaomyzon
Yanliaomyzon

The oldest fossils of stem-group lampreys date back to the late Devonian period, approximately 360 million years ago. Modern-looking lampreys only appeared during the Jurassic period, around 163 million years ago. Scientists believe the modern families likely split from one another between the Middle Jurassic and the end of the Cretaceous. Today, there are about 38 known living species. These are divided into three families: Geotriidae and Mordaciidae in the Southern Hemisphere, and Petromyzontidae in the Northern Hemisphere.

Lamprey skeleton lateral view
Lamprey skeleton lateral view

Lampreys possess a skeleton made of cartilage rather than bone. They also use a series of cartilaginous structures called arcualia, which sit above the notochord. This cartilaginous structure contributes to their efficiency as swimmers. Their swimming movements create low-pressure zones around the body. This allows them to pull themselves through the water rather than simply pushing. Many species also use countershading for camouflage. They have dark backs to blend with the ground and light undersides to blend with the surface.

スナヤツメ(南方種)
スナヤツメ(南方種)

The distribution and survival of lampreys are closely tied to water quality and habitat. They live mostly in temperate coastal and fresh waters. Some species, such as the sea lamprey, travel long distances in the open ocean. However, their larvae have a low tolerance for high water temperatures, which keeps them out of the tropics. Human activities like pollution, overfishing, and the construction of dams can disrupt their migration. Dams can block access to essential spawning grounds. Conversely, artificial channels have allowed some species, like the sea lamprey in the Great Lakes, to become invasive pests.

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🖼️ Images & Media (15)
File:Petromyzon marinus.jpg
Petromyzon marinus.jpg
File:Boca de lamprea.1 - Aquarium Finisterrae.JPG
Boca de lamprea.1 - Aquarium Finisterrae.JPG
File:Lamprey Anatomy (50693755972).jpg
Lamprey Anatomy (50693755972).jpg
File:Lamprey Larva x sect pharynx labelled.png
Lamprey Larva x sect pharynx labelled.png
File:Lamprey anatomy.png
Lamprey anatomy.png
File:Lamprey skeleton lateral view.jpg
Lamprey skeleton lateral view.jpg
File:スナヤツメ(南方種).jpg
スナヤツメ(南方種).jpg
File:Lamprey larva labelled.png
Lamprey larva labelled.png
File:Oeufs002b,57.png
Oeufs002b,57.png
File:Petromyzontiformes phylogeny.png
Petromyzontiformes phylogeny.png
File:Yanliaomyzon.png
Yanliaomyzon.png
File:Lamprey Anatomy.png
Lamprey Anatomy.png

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