Hagfishes, Class Myxini, Order Myxiniformes. Hagfishes, Class Myxini, Order Myxiniformes. Hagfishes, Class Myxini, Order Myxiniformes

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1 Formerly classified with lampreys in Agnatha, or Cyclostomata-not a monophyletic grouping 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. 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 1

2 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 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) Myxini No trace of vertebrae One semicircular canal No mineralized tissues Isomolar with seawater No lateral line Three accessory hearts No stomach Fibrous cranium support All other vertebrates 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 2

3 Myxini No trace of vertebrae One semicircular canal No mineralized tissues Isomolar with seawater No lateral line Three accessory hearts No stomach Fibrous cranium support All other vertebrates Vertebrae 2-3 semicircular canals Mineralized tissues Hypotonic to seawater Lateral line No accessory hearts Stomach 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) H 2 O and ionfl in body fluids than in surrounding water Fish is constantly losing H 2 O and gaining ions thru diffusion Fish makes up for H 2 O loss by drinking water which is highly saline Fish excretes small amounts of highly concentrated urine 3

4 Osmoregulation in fishes Hyperosmotic fishes (freshwater species) H 2 O fl and ion in body fluids than in surrounding water Fish is constantly gaining H 2 O and losing ions thru diffusion Fish makes up for H 2 O gain and ion loss by not drinking water and excreting large amounts of dilute urine Osmoregulation in fishes Hyperosmotic fishes (freshwater species) H 2 O fl and ion in body fluids than in surrounding water Fish is constantly gaining H 2 O and losing ions thru diffusion Fish makes up for H 2 O 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) Myxini No trace of vertebrae One semicircular canal No mineralized tissues Isomolar with seawater No lateral line Three accessory hearts No stomach Fibrous cranium support All other vertebrates Vertebrae 2-3 semicircular canals Mineralized tissues Hypotonic to seawater Lateral line No accessory hearts Stomach Cranium of cartilage or bone 4

5 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 5

6 Knotting Behavior Lampreys, Class Cephalaspidomorphi, closely related species Lampreys, Class Cephalaspidomorphi, 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 6

7 Lampreys, Class Cephalaspidomorphi, 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, 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, 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 7

8 Lampreys, Class Cephalaspidomorphi, 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, Lamprey life cycle 8

9 Ammocoete stage Ammocoete stage Lamprey life cycle Eggs hatch in days Lamprey life cycle Eggs hatch in days 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 9

10 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 10

11 Sea Lamprey, Petromyzon marinus First reported in 1890 but may be native Niagara Falls served as barrier to dispersal 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 11