Families Petromyzontidae 8 genera, ~ 40 species vt species

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Petromyzontiformes (Greek petro- (rock) and –myzo (suck))
Taxonomy: Superclass Agnatha - jawless fishes

Class Cephalaspidomorphi

Order Petromyzontiformes - lampreys

Families Petromyzontidae

8 genera, ~ 40 species

VT species: Ichthyomyzon – single dorsal fin (silver lamprey, northern brook lamprey)

Petromyzon – two dorsal fins (sea lamprey)

Lampetra – fewer circumoral teeth (American brook lamprey)
Description: primitive, jawless, cartilaginous, anguilliform fishes with no scales or paired fins, one or two dorsal fins and caudal fin, gill pores or slits; vertebrae present

Larvae are a few centimeters long, lack well-developed eye; adults may reach 0.6 m

Mouth of adults is a suction disk with circumoral teeth for attachment, and a few, large, rasping teeth on a ‘tongue’

Unlike Myxini, they have two semicircular canals, lateral line system, well developed eyes in adults

Habitat: Anadromous or in streams
Distribution: N. and S. America, Australia, New Zealand, Europe
Ecology and life history: Long larval stage (ammocoetes) in freshwater streams (2-7 years), followed by short adult stage in fresh or salt water (1 month - 2 years)

Highly fecund (60,000 -300,000 eggs)

Larval forms generally detritus feeders; adults may be parasitic on fish, or non-feeding

Parasitic species undergo metamorphosis, feed in fresh or salt water as juveniles, then return to streams as adults to spawn.

Non-parasitic species are stream-resident, do not feed after metamorphosis, and spawn soon after metamorphosis

Parasitic form appears to be the ancestral type

Some Australian species are predatory rather than parasitic
Additional details: lamprey were harvested in Europe for centuries as a delicacy; populations are now endangered throughout much of Europe due to habitat degradation. Parasitic sea lamprey (Petromyzon marinus) invaded the Great Lakes in the 1930s and have caused major economic and ecological damage to fisheries.
References used:

Bond, C. E. 1996. Biology of Fishes, 2nd. ed. Saunders College Publishing, Fort Worth

Paxton, J. R. and W. N. Eschmeyer. 1998. Encyclopedia of fishes 2nd ed. Academic Press.

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