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
Myxini
• No trace of vertebrae
All other vertebrates
• Vertebrae (rudimentary arch
• One semicircular canal
strucutes in lampreys
• No mineralized tissues
• 2-3 semicircular canals
• Isomolar with seawater
• Mineralized tissues
• No lateral line
• Hypotonic to seawater
• Three accessory hearts
• Lateral line (pores in lamprey)
• No stomach
• No accessory hearts
• Fibrous cranium support
• Stomach
• Cranium of cartilage or bone
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Hagfishes, Class Myxini, Order Myxiniformes
All other vertebrates
Myxini
• No trace of vertebrae
• Vertebrae
• One semicircular canal
• 2-3 semicircular canals
• No mineralized tissues
• Mineralized tissues
• Isomolar with seawater
• Hypotonic to seawater
• No lateral line
• Lateral line
• Three accessory hearts
• No accessory hearts
• No stomach
• Stomach
• Fibrous cranium support
• Cranium of cartilage or bone
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 H 2O and gaining ions thru
diffusion
•Fish makes up for H 2O loss by drinking water which is
highly saline
•Fish excretes small amounts of highly concentrated
urine
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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 H 2O and losing ions thru
diffusion
•Fish makes up for H 2O gain and ion loss by not drinking
water 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 H 2O and losing ions thru
diffusion
•Fish makes up for H 2O gain and ion loss by not drinking
water 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
Myxini
All other vertebrates
• No trace of vertebrae
• Vertebrae
• One semicircular canal
• 2-3 semicircular canals
• No mineralized tissues
• Mineralized tissues
• Isomolar with seawater
• Hypotonic to seawater
• No lateral line
• Lateral line
• Three accessory hearts
• No accessory hearts
• No stomach
• Stomach
• Fibrous cranium support
• Cranium of cartilage or bone
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Lateral line in fishes
A system of mechanoreptors that detect water
movement or pressure change near fish’s body
Neuromasts - made up of individual hair cells
Lateral line in fishes
A system of mechanoreptors that detect water
movement 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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Lamprey life cycle
Eggs hatch in
12-14 days
Ammocoete stage
Lamprey life cycle
Eggs hatch in
12-14 days
Ammocoete stage
Free living species metamorph into adults and immediately
return to spawning site to mate and then die
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 1890
but may be native
Sea Lamprey, Petromyzon marinus
First reported in 1890
but may be native
Niagara Falls served as
barrier to dispersal
Welland Canal was built to allow ships to get
around Niagara Falls
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Sea Lamprey, Petromyzon marinus
First reported in 1890
but may be native
1946
1936
Niagara Falls served as
barrier to dispersal
1921
Sea Lamprey, Petromyzon marinus
Sea Lamprey, Petromyzon marinus
Control measures
•Physical barriers to spawning streams
•Releasing sterilized males
•Application of a lampricide (TFM) - poured into streams
known to harbor ammocoetes, specific to ammocoetes
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