hagfishes, class myxini, order myxiniformeswwn.inhs.illinois.edu/~chrisp/lower vert/ib 496 lec...
TRANSCRIPT
1
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
2
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
3
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
4
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
5
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
6
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
7
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
8
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
9
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
10
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
11
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