Marine Fishes

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Marine Fishes

• Chapter 12

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General Info on Fish

• They are the most common and diverse group of
  animals with backbones in the ocean and in the
  world
• They are an ancient group their origins date
  back more than 500 million years
• There are about 20,000 different species of fish
  found worldwide in both marine and freshwater
  ecosystems
• They appear in a wide variety of shapes, sizes,
  colors

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Protochordates and Jawless Fishes

• Animals with backbones (spinal chords) are called
  chordates
• Fish have a hollow, dorsal nerve chord called a
  notochord
• A notochord is a flexible, rodlike structure that
  supports the spinal chord
• Protochordates are organisms that have a
  notochord, but lack certain advanced structures
  that other fish have, so they are called
  primitive chordates

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Protochordates and Jawless Fishes

• Fish that are higher chordates are also the first
  vertebrates
• Vertebrates are animals characterized by having a
  skeleton, backbone, skull and brain
• The higher chordates include all the vertebrates
  fish, amphibians, reptiles, birds, and mammals
• Protochordates are interesting to scientists
  because their ancestors seem to represent the
  evolutionary link between invertebrates and
  vertebrates!

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Jawless Fishes

• Most fish, as you can observe, have movable mouth
  parts called JAWS
• There are a few species of fish, however, that do
  not
• Hundreds of millions of years ago, the oceans
  were inhabited by jawless fishes
• These were the first types of fish to evolve
• Jawless fishes are the most primitive of the
  vertebrates because they have no jaws and dont
  have a true backbone

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Jawless Fishes

• There are only 2 types of jawless fishes alive
  today
• They are the hagfish and the lamprey
• They are in a class called Agnatha (it means
  without jaws
• Some can grow up to 1m in length
• These fish live as parasites
• The lamprey inhabits estuaries from Maine to
  Florida
• It uses a sucking disk on its mouth to attach to
  living fish in rivers
• It feeds by using its teeth and rasping tongue to
  make a hole in the body of the host fish
• The lamprey then sucks blood out of its tissues

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Hagfish
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Lamprey
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Cartilaginous Fish

• Feel the tip of your nose and your ears. Go
  ahead, Ill wait!
• They feel soft because they are made from
  cartilage, a flexible connective tissue made of
  cells and protein
• Cartilaginous fishes have bodies whose entire
  skeletons are made of cartilage
• They are in the class Chondrichthyes (it means
  cartilage fishes
• This class include such fishes as sharks, skates,
  and rays

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Whale Shark
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Great White Shark
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Tiger Shark
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Skates
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Rays
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Characteristics of Cart. Fish

• There are fewer than 700 species, as opposed to
  more than 25,000 species of bony fish
• These were the first jawed fish to evolve
• Cart. Fish have placoid scales, which are
  actually tiny teeth that are deeply embedded in
  the skin (and they point backwards)
• If you were to pet a shark from head to tail, it
  would feel like rough sandpaper
• However, I strongly suggest that you NEVER
  attempt to pet a shark!
• Cart. Fish have visible gill slits for breathing,
  while bony fish have theirs concealed by a skin
  flap

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Skates and Rays

• Most are bottom dwellers
• They have very well developed pectoral fins
• The up and down movements of these fins resemble
  the wings of a bird in flight
• Stingrays are often found concealed in the sands
  of the Gulf of Mexico and along the Atlantic
  coast from the Carolinas to Brazil
• A sharp spine near the base of its tail can
  inflict a painful, sometimes deadly stab wound

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R.I.P. Steve Irwin!
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Sharks!

• There are about 350 known species of sharks
• The smallest is the pigmy shark, which is about
  25cm long
• The biggest shark (in fact, the biggest fish) is
  the whale shark, which can be more than 15m in
  length
• The whale shark is harmless because they are
  filter feeders that consume plankton
• Some sharks are bottom dwellers that have
  crushing teeth and eat mollusks
• Nurse sharks and leopard sharks are examples of
  this

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Shark Anatomy
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Shark Internal Anatomy
Nostrils
Mouth
Heart
Gill Slits
Pectoral Fin
Gall Bladder
Testis
Liver
Liver
Stomach
Pylorus
Spleen
Rectal Gland
Spiral Valve Intestine
Pelvic Fin
Claspers
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Nurse Shark
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Leopard Shark
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Great Whites

• This is one species of shark that can be
  dangerous to humans
• Though it feeds on marine mammals such as seals
  and sea lions, great whites have attacked and
  killed humans before
• The biggest great whites ever caught weighed over
  1200kg and measured from 5 to nearly 6.5m long
• While great whites have killed humans in the
  past, these deaths are accidental in nature
• What do you think this means?

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Sharks

• Other sharks that have killed humans are the
  tiger shark, the bull shark, and the hammerhead
• Tiger sharks prey on sea turtles, seals, and
  other smaller sharks
• Bull sharks are an aggressive species of shark
  that are found in some freshwater areas as well
• Hammerheads have 2 lateral projections on their
  heads with eyes at the end
• The more predatory sharks like these have sharp,
  serrated teeth for catching and cutting up their
  prey

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Bull Shark
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Sharks

• Sharks have been on this planet for more than 300
  million years
• They closely resemble their ancestral forms, and
  havent needed to evolve
• They are sometimes called evolutionary
  dead-ends or living fossils
• What structures do they possess that have allowed
  them to remain on this planet for so long, never
  needing to change?

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Shark Structures and Behavior

• Sharks have very sensitive receptors for the
  detection of stimuli
• The lateral line organ, along each side of a
  sharks body, can pick up sound vibrations over
  great distances
• The sharks sense of smell is so sensitive and
  acute that it can detect a drop of blood nearly
  half a km away
• In fact, nearly 2/3 of a sharks brain is devoted
  to its sense of smell
• Sharks also have receptors called ampullae of
  Lorenzini in their snout these can detect
  electric fields given off by prey in their muscle
  movement

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Shark Anatomy
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Sharks

• After detecting prey, sharks are more than well
  equipped to catch and eat them
• Sharks can move very quickly through the water
  because of their body shape
• They also have several rows of sharp teeth the
  rows at times move forward to replace lost teeth
• At any given time, sharks can have hundreds of
  teeth in its mouth!

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Great White Shark Teeth
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Bony Fishes!

• More than 95 of all fish on Earth belong to the
  class Osteichthyes (meaning bony fishes)
• These fish have a skeleton of bone, rather than
  cartilage
• They have a backbone with a chain of vertebrae,
  just like humans!
• They are found in every type of aquatic
  environment
• They all have protective scales which are
  attached loosely to the skin and may even rub off
  on your hands!
• Fish feel slimy because they secrete a protective
  mucous that helps fight infection, and also
  allows them to move quicker through the water

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Bony Fishes

• The gills of bony fish are located in the head
  region, on either side of the body
• The gills are covered with a flap of tissue
  called an operculum, which opens and closes every
  time the fish breathes
• Fish breathe by taking water into its mouth
• The water contains Dissolved oxygen, and the
  water moves from the mouth over the gills
• The gills have filaments attached to them that
  allows the oxygen to diffuse into them
• The DO is then passed into the blood

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Bony Fish

• One of the defining characteristics of fish is
  the fact that they have fins
• These are mainly used for swimming, and any
  marine animal that has the ability to swim is
  called nekton
• Swimming can be tiring, so fish need the ability
  to be able to rest to float in place
• They do this by a gas filled organ called a swim
  bladder
• By regulating the volume of gas in its swim
  bladder, a fish can rise, sink, or stay in
  position in the water
• What is the ability to stay afloat in water
  called?

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Interesting Fish Facts

• Fish have been on the earth for more than 450
  million years
• Eggs of Seahorses are fertilized and reared by
  the males!
• Some fish like sharks don't posses an air bladder
  to help keep them afloat and must either swim
  continually or rest on the bottom
• Fish feel pain and suffer stress just like
  mammals and birds
• Tropical fish are one of the most popular pets in
  the U.S.
• Every year, fish scales grow and growth rings are
  produced so you can tell how old a fish is by
  counting the rings! (just like with trees)