Marine Fishes

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Marine Fishes

• Pelagic organisms that can actively swim (against
  a current) are known as nekton

• Nekton include some invertebrates such as
  cephalopods and pelagic arthropods such as shrimp
  and swimming crabs, but most nekton are
  vertebrates

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Phylum Chordata, Subphylum Vertebrata

• Vertebrates (subphylum Vertebrata) share four
  fundamental characteristics of the phylum
  Chordata with 2 invertebrate subphyla
• Subphylum Urochordata
• Subphylum Cephalochordata
• Vertebrates differ, however, in
  the presence of a backbone, or
  spine, and the presence of an
  endoskeleton

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Subphylum Vertebrata

• The vertebral backbone consists of a dorsal row
  of hollow skeletal elements, the vertebrae
• The vertebrae surround and protect the nerve
  cord, or spinal cord, which ends in a brain
  protected by a skull made of cartilage or bone
• Vertebrates exhibit bilateral symmetry and have a
  distinct head, and organ systems

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Subphylum Vertebrata
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Marine Fishes

• Fishes were the first vertebrates, appearing more
  than 500 million years ago

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Marine Fishes

• Fishes are the oldest and structurally-simplest
  of all living invertebrates
• Half of all vertebrates are fish!
• Most species of fish are marine
• Three groups are fish are currently recognized
• Jawless Fishes (superclass Agnatha)
• Cartilaginous Fishes (class Chondrichthyes)
• Bony Fishes (superclass Osteichthyes)

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General Fish Morphology
http//www.users.totalise.co.uk/darrenbarton/id11
9.htm
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Jawless Fishes (Agnatha)

• The most primitive of all living fish are the
  jawless fish (Agnatha)
• As they lack jaws, jawless fish must feed by
  suction with the aid of a round, muscular mouth
  and rows of teeth
• Body is cylindrical and elongated like that of an
  eel or snake no paired fins or scales
• lack true vertebral column!
• Cartilaginous skeleton

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Jawless Fish (Agnatha)

• Jawless fish include the hagfish and the lampreys
• Hagfish feed mostly on dead or dying fishes
  usually found on deep, muddy bottoms
• Exclusively marine
• Lampreys attach themselves to other living fishes
  and suck their blood and tissue matter
• Primarily freshwater

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Hagfish (left) vs. Lamprey (right)
http//chrisortlepp.com/photos/Hagfish-coiled.jpg
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Cartilaginous Fishes

• Cartilaginous fishes (Chondrichthyes) have a
  skeleton made not of bone, but of cartilage,
  which is lighter and more flexible than bone
• Cartilaginous fishes have well-developed jaws and
  paired fins for efficient swimming
• Most cartilaginous fish also have rough,
  sandpaper-like skin, the result of placoid scales

pointed tip directed backwards
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Cartilaginous Fishes

• Cartilaginous fishes include sharks, skates, rays
  and chimeras, or ratfishes
• Nearly all are marine
• 350 species of sharks 500 species of skates
  and rays 30 species of chimeras

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Sharks (cue scary, cello music)

• Sharks are often referred to as living fossils
  because many of the species alive today are
  similar to ones that swam the seas gt100 million
  years ago
• Sharks have powerful jaws with rows of numerous
  sharp, often triangular teeth
• Lost or broken teeth are quickly replaced by
  another, which shifts forward from the row behind
  it as if on a conveyor belt

http//www.evolutionnyc.com//ImgUpload/P_455917_96
4647.jpg
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Sharks

• Sharks have fusiform, spindle-shaped bodies,
  which cut easily through the water
• A well-developed, muscular caudal fin propels
  them through the water paired pectoral fins
  enable steering and dorsal fins provide stability

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Sharks are efficient predators

• Many sharks exhibit counter-shading, appearing
  dark on top and light on the bottom
• Camouflage from above and below
• Why?

flmnh.ufl.edu
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Sharks, dog bites, lightning strikes, and falling
coconuts, oh my!

• Sharks have five to seven gill slits which are
  located behind the head for respiration (well
  come back to this)
• More than 80 of all sharks are under 2 meters in
  length (less than 6.6 feet), and only a few of
  the remaining 20 are aggressive towards humans
• FACT You are more likely to die from a dog bite
  (or lightening strike) than a shark bite

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Fish are friends, not food

• In fact, sharks have WAY more to fear from humans
  than we do of sharks
• Shark populations are in considerable decline
  worldwide
• 80 global decline in shark populations!
• 26-73 million sharks killed every year for their
  fins!
• Potential increases in diseased,
  unfit, and unhealthy prey
  individuals

all-creatures.org
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Dramatic decline in shark populations
Myers, et al. 2007
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Is your dinner endangered?
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Rays and Skates

• Rays and skates have dorsoventrally flattened
  bodies, with 5 pairs of gill slits on the
  underside (ventral side) of their body
• Most are demersal, spending much of their lives
  on the sea floor
• Pectoral fins are
  greatly extended
  
  resembling wings

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Is it a ray, or a skate?

• Skates usually have 2 dorsal fins Rays lack
  dorsal fins altogether
• Skates have a muscular tail Rays have a
  whip-like tail, usually with a prominent stinger

Ray
Skate
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Chimeras, or ratfishes

• Approximately 30 species of deep-water,
  strange-looking cartilaginous fish are grouped
  separately as chimeras, or ratfishes
• Only one pair of gill slits, covered by a flap of
  skin
• Demersal (bottom-dwelling)
• Some with a long,
  rat-like tail

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To summarize.
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Bony Fishes (Osteichthyes)

• Bony fish (Osteichthyes) are the most successful
  and abundant of the 2 groups of fishes (96 of
  all fish 27,000 species)
• Osteichthyes possess a hard, strong - but
  lightweight - skeleton made of calcium that
  supports them and is responsible for their
  success (and diversity) as a group
• Bony fish include tuna, cod, flounder, goldfish,
  and other familiar species

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Bony Fishes (Osteichthyes)

• The composition of their skeleton is not the only
  distinguishing feature of bony fishes
• In contrast to the tiny, pointed placoid scales
  of cartilaginous fishes, bony fish usually have
  cycloid or ctenoid scales, which are thin,
  flexible, and overlapping
• Cycloid scales have a smooth outer edge
• Ctenoid scales have a toothed outer edge

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Bony Fishes (Osteichthyes)

• The scales are made of bone and are covered by a
  thin layer of skin and a protective mucus
• Bony fish are also characterized by the presence
  of a gill flap, or operculum

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Bony fish have a bony opeculumCartilaginous fish
have gill slits
kmle.co.kr
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Bony Fishes (Osteichthyes)

• Bony fish are subdivided into two major groups
• Lobe-finned fishes
• Ray-finned fishes
• Lobe-finned fishes are largely extinct, but
  include lungfishes and coelacanths
• Ray-finned fishes, in contrast, are far more
  successful, and can be further divided into
  soft-rayed and spiny-rayed bony fish

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Soft-rayed vs. Spiny-rayed

• Soft rayed fish representatives include
• Cod
• Trout
• Herring
• Spiny-rayed fish representatives include
• Bass
• Groupers
• Reef fish

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Fishes of Long Island
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Fishes of Long Island
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Flatfish (doormats) of Long Island
KEY Right-sided Left-sided
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Ontogeny recapitulates phylogeny?!!?
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