#petromyzontida

[herpsandbirds]

Pacific Lamprey (Entosphenus tridentatus), family Petromyzontidae, order Petromyzontiformes, in a stream in the Santa Cruz Mountains, CA, USA

photograph by Anton Sorokin

[bestanimal]

Round 2 - Chordata - Petromyzontida

(Sources - 1, 2, 3, 4)

Petromyzontida is a class comprising one order, Petromyzontiformes, commonly called “lampreys.”

Like their closest living relatives, the hagfish, lampreys bear a cartilaginous skull and rudimentary vertebrae. Adults lack a jaw, and are characterized by a toothed, funnel-like, sucking mouth. They have elongated, eel-like bodies reaching up to 1.3 metres (3.9 ft) long. They have one nostril atop the head, seven gill pores on each side of the head, two well-developed eyes, and two parietal eyes. Only 18 species are predators or scavengers, the rest (all freshwater species) do not feed as adults, instead living off the reserves gained as juveniles. Carnivorous species are marine, though 9 of them migrate into freshwater to breed. They use the suction cup around their mouths to cling to rocks or prey, using their tongue to either rasp blood from prey or algae from rocks. They also use this suction cup to climb up rocks when migrating upstream to breed.

Adult lampreys spawn in nests of sand, gravel and pebbles in clear streams. After hatching from their eggs the larvae, called ammocoetes, will drift downstream with the current until they reach soft and fine sediment in which to burrow, taking up an existence as filter feeders, collecting detritus, algae, and microorganisms (image 4). Their eyes are underdeveloped, only capable of discriminating changes in light. Lampreys spend the majority of their lives as these filter-feeding ammocoetes. Most species spend up to 8 years, though some may spend as little as 1-2 years. The ammocoetes will then undergo a metamorphosis which generally lasts 3-4 months, during which they do not eat.

The oldest fossil lamprey, Priscomyzon, is known from the Late Devonian. Other stem-group lampreys, like Pipiscius, Mayomyzon and Hardistiella are known from the Carboniferous. While they appear relatively unchanged, stem-lampreys lack the specialised, heavily toothed discs with plate-like laminae present in modern lampreys, and their larvae resembled the adults, rather than having a distinct stage. The earliest lamprey with the specialised toothed oral disc typical of modern lampreys is Yanliaomyzon from the Middle Jurassic.

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Many species change color as ammocoetes, becoming dark during the day and pale at night.

Lampreys have been extensively studied because their relatively simple brain is thought to reflect the brain structure of early vertebrate ancestors, thus providing insight into our origins.

Lampreys are valued as food in the Northwest United States, throughout Europe, in Russia, Japan, and in South Korea. King Henry I of England is claimed to have been so fond of lampreys that he often ate them, late into life and poor health, against the advice of his physician concerning their richness, and is said to have died from eating "a surfeit of lampreys".

In the county of Nakkila (Finland) and Carnikava Municipality (Latvia), the European River Lamprey (Lampetra fluviatilis) is the local symbol, found on their coats of arms.

The legend of the Lambton Worm from County Durham in North-East England concerns a lamprey being fished out of the River Wear by a young boy skipping church. He declares that he had “caught the devil” and disposes of it down a nearby well. Over the years, the lamprey grows into a giant, poisonous Worm, wrapping itself around a local hill and terrorizing the village. Hijinks and witch-curses ensue.

Lampreys were highly appreciated by the Ancient Romans, not only as food, but also as pets. Lucius Licinius Crassus was mocked by Gnaeus Domitius Ahenobarbus for weeping over the death of his pet lamprey, who he was said to have adorned with earrings and small necklaces, training it to respond to its name and swimming up to eat what was offered. Crassus retorted that Domitius had lost three wives himself and Crassus had never seen him shed a tear.

Publius Vedius Pollio was reportedly an exceedingly cruel Roman soldier who kept a pool of carnivorous lampreys to which he would feed slaves who had displeased him. This went on until Gaius Julius Caesar Augustus was visiting his mansion and witnessed Pollio about to dispatch a slave who had broken a crystal cup. Augustus had all of Pollio’s cups destroyed, as well as his mansion, and filled in his pond. This is likely an urban legend, but honestly, I feel like it should have ended with Pollio going down with the lampreys.

Dams and other human development have made it hard for lampreys to migrate upstream to breed. Some scientists are hoping to design ramps that will utilize lamprey’s climbing ability so that they can bypass dams.

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