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Hagfishes, Class Myxini, Order Myxiniformes

• Formerly classified with lampreys in Agnatha, or Cyclostomata-not a monophyletic grouping

Hagfishes, Class Myxini, Order Myxiniformes

• Formerly classified with lampreys in Agnatha, or Cyclostomata-not a monophyletic grouping

• Marine, cosmopolitan temperate distribution, 43 species, occur at depths ranging from 1 to 1800 ft.

Hagfishes, Class Myxini, Order Myxiniformes

• Formerly classified with lampreys in Agnatha, or Cyclostomata-not a monophyletic grouping

• Marine, cosmopolitan temperate distribution, 43 species, occur at depths ranging from 1 to 1800 ft.

• Nocturnal predators of small benthic invertebrates, scavenge on dead or dying fish, enter the body cavity and eat the dead organism from the inside out

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Hagfishes, Class Myxini, Order Myxiniformes

• Formerly classified with lampreys in Agnatha, or Cyclostomata-not a monophyletic grouping

•Marine, cosmopolitan temperate distribution, 43 species, occur at depths ranging from 1 to 1800 ft.

• Nocturnal predators of small benthic invertebrates, scavenge on dead or dying fish, enter the body cavity and eat the dead organism from the inside out

• Represent the earliest extant lineage of vertebrates

Hagfishes, Class Myxini, Order Myxiniformes

• Formerly classified with lampreys in Agnatha, or Cyclostomata-not a monophyletic grouping

•Marine, cosmopolitan temperate distribution, 43 species, occur at depths ranging from 1 to 1800 ft.

• Nocturnal predators of small benthic invertebrates, scavenge on dead or dying fish, enter the body cavity and eat the dead organism from the inside out

• Represent the earliest extant lineage of vertebrates

• Oldest fossil is from the Carboniferous of Illinois (300 Ma)

Hagfishes, Class Myxini, Order Myxiniformes

• No trace of vertebrae• One semicircular canal• No mineralized tissues• Isomolar with seawater• No lateral line• Three accessory hearts• No stomach• Fibrous cranium support

• Vertebrae (rudimentary arch strucutes in lampreys• 2-3 semicircular canals• Mineralized tissues• Hypotonic to seawater• Lateral line (pores in lamprey)• No accessory hearts• Stomach• Cranium of cartilage or bone

Myxini All other vertebrates

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Hagfishes, Class Myxini, Order Myxiniformes

• No trace of vertebrae• One semicircular canal• No mineralized tissues• Isomolar with seawater• No lateral line• Three accessory hearts• No stomach• Fibrous cranium support

• Vertebrae• 2-3 semicircular canals• Mineralized tissues• Hypotonic to seawater• Lateral line• No accessory hearts• Stomach• Cranium of cartilage or bone

Myxini All other vertebrates

Osmoregulation in fishes

Given the permeability of the gill tissue, most passive (diffusive) ion exchange occurs there

Active transport occurs through mouth and anus

Osmoregulation in fishes

Hyposmotic fishes (marine species)•H2O › and ionfl in body fluids than in surrounding water

•Fish is constantly losing H2O and gaining ions thrudiffusion•Fish makes up for H2O loss by drinking water which ishighly saline•Fish excretes small amounts of highly concentratedurine

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Osmoregulation in fishes

Hyperosmotic fishes (freshwater species)•H2O fl and ion › in body fluids than in surrounding water

•Fish is constantly gaining H2O and losing ions thrudiffusion•Fish makes up for H2O gain and ion loss by not drinkingwater and excreting large amounts of dilute urine

Osmoregulation in fishes

Hyperosmotic fishes (freshwater species)•H2O fl and ion › in body fluids than in surrounding water

•Fish is constantly gaining H2O and losing ions thrudiffusion•Fish makes up for H2O gain and ion loss by not drinkingwater and excreting large amounts of dilute urine

In general, most fishes are able to tolerate short term exposure to salinity changes

Diadromous species (salmon, some sharks) can tolerate a wide range of salinities (=euryhaline)

Hagfishes, Class Myxini, Order Myxiniformes

• No trace of vertebrae• One semicircular canal• No mineralized tissues• Isomolar with seawater• No lateral line• Three accessory hearts• No stomach• Fibrous cranium support

• Vertebrae• 2-3 semicircular canals• Mineralized tissues• Hypotonic to seawater• Lateral line• No accessory hearts• Stomach• Cranium of cartilage or bone

Myxini All other vertebrates

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Lateral line in fishes

A system of mechanoreptors that detect watermovement or pressure change near fish’s body

Neuromasts - made up of individual hair cells

Lateral line in fishes

A system of mechanoreptors that detect watermovement or pressure change near fish’s body

Neuromasts - made up of individual hair cells

Water flows past neuromasts via canal pores

Hagfishes, Class Myxini, Order Myxiniformes

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Hagfishes, Class Myxini, Order Myxiniformes

Knotting Behavior

Lampreys, Class Cephalaspidomorphi, Order Petromyzontiformes

• Either parasitic or non-parasitic, both in same species or closely related species

Lampreys, Class Cephalaspidomorphi, Order Petromyzontiformes

• Either parasitic or non-parasitic, both in same species or closely related species--satellite species hypothesis

• Anadromous or freshwater, N. Amer., Eur., Aust., N.Z., 41 species, 32 entirely freshwater, 18 parasitic, 4 parasitic and 3 free living species occur in Illinois

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Lampreys, Class Cephalaspidomorphi, Order Petromyzontiformes

• Either parasitic or non-parasitic, both in same species or closely related species--satellite species hypothesis

• Anadromous or freshwater, N. Amer., Eur., Aust., N.Z., 41 species, 32 entirely freshwater, 18 parasitic , 4 parasitic and 3 free living species occur in Illinois

• Adults die after spawning

Lampreys, Class Cephalaspidomorphi, Order Petromyzontiformes

• Either parasitic or non-parasitic, both in same species or closely related species--satellite species hypothesis

• Anadromous or freshwater, N. Amer., Eur., Aust., N.Z., 41 species, 32 entirely freshwater, 18 parasitic, 4 parasitic and 3 free living species occur in Illinois

• Adults die after spawning

• Larval stage, ammocoete -free living, blind, filter feeding

Lampreys, Class Cephalaspidomorphi, Order Petromyzontiformes

• Either parasitic or non-parasitic, both in same species or closely related species--satellite species hypothesis

• Anadromous or freshwater, N. Amer., Eur., Aust., N.Z., 41 species, 32 entirely freshwater, 18 parasitic, 4 parasitic and 3 free living species occur in Illinois

• Adults die after spawning

• Larval stage, ammocoete -free living, blind, filter feeding

• Non-parasitic adults do not feed, live for six months and spawn

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Lampreys, Class Cephalaspidomorphi, Order Petromyzontiformes

• Either parasitic or non-parasitic, both in same species or closely related species--satellite species hypothesis

• Anadromous or freshwater, N. Amer., Eur., Aust., N.Z., 41 species, 32 entirely freshwater, 18 parasitic, 4 parasitic and 3 free living species occur in Illinois

• Adults die after spawning

• Larval stage ammocoete -free living, blind, filter feeder

• Non-parasitic adults do not feed, live for six months and spawn

• Parasitic species will feed and live for 1 to 3 years

Lampreys, Class Cephalaspidomorphi, Order Petromyzontiformes

Lamprey life cycle

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Eggs hatch in 12-14 days

Amm

ocoete stage

Lamprey life cycle

Eggs hatch in 12-14 days

Amm

ocoete stage

Free living species metamorph into adults and immediatelyreturn to spawning site to mate and then die

Lamprey life cycle

Sea Lamprey, Petromyzon marinus

• Anadromous species native to both sides of the North Atlantic

• Large parasitic species (up to 3’), can kill up to 40 lbs. of prey in lifetime

• Classic example of the deleterious effects of an exotic species initiated by man-made habitat alterations

• But also one of the few examples of successful control of exotic species

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Sea Lamprey, Petromyzon marinus

First reported in 1890but may be native

Sea Lamprey, Petromyzon marinus

First reported in 1890but may be native

Niagara Falls served as barrier to dispersal

Welland Canal was built to allow ships to getaround Niagara Falls

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Sea Lamprey, Petromyzon marinus

First reported in 1890but may be native

Niagara Falls served as barrier to dispersal

19211936

1946

Sea Lamprey, Petromyzon marinus

Sea Lamprey, Petromyzon marinusControl measures

•Physical barriers to spawning streams

•Releasing sterilized males

•Application of a lampricide (TFM) - poured into streams known to harbor ammocoetes, specific to ammocoetes