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The 4 basic characteristics of chordates….
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Have a single, dorsal, hollow nerve chord
Gill or pharyngeal slits
a notochord
a post anal tail
Agnatha ("no jaws") is a superclass of
jawless fish in the phylum Chordata,
subphylum Vertebrata.
 gnathostomes- all vertebrates with jaws
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Has no paired fins or scales
Lampreys (30 species)
Temperate regions, primarily freshwater
breed in rivers/lakes
attach to other fish and suck their blood, or feed
on bottom invertebrates
 Hagfish/slime eels (20 Species)
 Feed on dead and dying things
 Bore into pray and eat them from the
inside out
 Live in burrows, in muddy bottoms
 Skin is used to make leather
 http://video.nationalgeographic.com/video/news
/animals-news/new-zealand-hagfish-slime-vin/
 Cartilaginous
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fishes
Includes: Sharks, rays and skates and ratfishes
Skeleton made of cartilage
Moveable jaws
Have paired lateral fins
Placoid scales
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Sharks
› fast swimming + predatory feeding
› living fossils (similar to the sharks that swam 100 mil yr
ago)
 Well developed caudal fin
› Heterocercal- upper lobe is longer than the lower lobe
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First dorsal fin longer and almost triangular
Paired pectoral fins, large and pointy
5-7 gill slits behind head
Lots of rows of teeth
› http://animal.discovery.com/tv-shows/other/videos/spy-on-
the-wild-basking-shark.htm
› http://www.youtube.com/watch?v=EukudEBC_hY
Hammerhead sharks (sphyrna)
Sawsharks (Pristiophorus)
Size varies
Pygmy shark
Whale shark
found in tropical waters, are filter feeders
Basking shark
Great White
Bull shark may live in rivers
Several sharks are only found in deep water
Shark meat is eaten round the world and overfishing is
common
Sharks still fished for oil and skin and fins used for
soup in the Orient
450-550 species
Dorsoventrally flattened bodies
demersal - fishes that live on the bottom
Have gills on their underside (located ventrally)
Stingrays:
Many species have a whiplike tail
Feed on clams, crabs, small fishes and small
animals in sediment
http://www.youtube.com/watch?v=ufxGw8EqY5
Q
 Electric
Rays have special organs, that
produce that produce electricity on
both sides of their head
› Romans and Greeks used them to help
headaches and other ailments
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Skates lay egg cases
 The larger species are hunted by humans for
food
 Similar to rays in appearance and feeding but
lack whip like tail and spines
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Ratfishes
 deep water fish, cartilaginous
 Feed on bottom dwelling crustations and
mollusks
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 http://www.youtube.com/watch?v=yCsa-YLTQVQ
Have cycloid or ctenoid scales - are flexible, thin, and overlap
cycloid scales- smooth
ctenoid scales- have many spikes on the exposed borders
The scales are made of bone, covered by a thin layer of skin and a
protective layer of mucus
They have an operculum- a gill cover which is a flap of bony
plates and tissue that protects the gills
The upper and lower lobes of the caudal fin are generally the
same size (homocercal )
Mouth is terminal (located at the anterior end )
Jaws are protrusible, b/c they can be projected outward from
the mouth
Have a swim bladder- gas filled sack, just above the stomach
and intestines
allows fish to adjust its buoyancy to keep it stable, compensates for
bone skeleton
Ichthyology- study of fishes
 Body shape is directly related to it's lifestyle
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› fast swimmers have a streamlined shape
› Laterally compressed seen on many inshore fish
› Many demersal fishes are dorsoventrally
flattened
 some are laterally flattened
› eels-like fishes - distinctly elongated
› slow fish- elongated vertically, triangular and
truncate or round
› And random shapes
› Body shapes can be used for camouflage
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Chromatophores - cells where pigments are found
structural colors- result when a special surface reflects a
certain type of light
› Mostly because of crystals that act like little mirrors
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Some change colors with mood, or reproductive
condition
› used to advertise that they're dangerous, taste bad,
poisonous
 know as warning coloration,
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Disruptive coloring- the presence of color stripes, bars or
spots used to break up the outline of the fish
› common in coral reef fish
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Open water and shallow water fish are rarely as colorful
Deep water fish tend to be either black or red, both are
extremely hard to see in the deep ocean
Swimming, its needed to... feed, reproduce,
escape, to get water through their gills
Swimming types….
Swim with side to side motion of either the body or
the tail
S-shaped contractions produced by bands of
muscle called myomeres, which run along the sides
the body, attached to the back bone for support
Sharks tend to sink, to fix this they have large stiff pectorals
that provide lift
Oil rich liver
Skates and Rays use the pectoral fins to provide the lift
Bony fishes have more maneuverability because of swim
bladder
Dorsal and anal fins are used as rudders and provide stability
Some fish like tuna just use sheer speed
most sharks are carnivores
Nurse shark
Cookie cutter shark
Lots of cartilaginous fish are filter feeders
filter water with gill rakers- slender projections on the inner surface of the gill arches
Digestion
food passes through the pharynx through the esophagus and into the stomach
stomach is typically J-shaped or elongated
Food then passes into the intestines
Other enzymes are secreted in the walls of the inner walls of the digestive track and in the
pancreas
Liver secretes bile needed to down fat
Carnivorous fish have short straight intestines
Fish that eat seaweed have coiled intestines
The intestines of cartilaginous fishes contain spiral valve which increases the internal
surface area of the intestine
the intestine is responsible for absorbing nutrients
Undigested material passes through the anus or the cloaca
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All fishes have a 2 chambered heart that is
located below the gills
› Sharks have to swim constantly to keep their heart
working
 Nurse shark doesn't have to do this (uses mouth opening
and closing to force water through their gills)
› In cartilaginous fish every gill lies in its own chamber
and each chamber opens to the outside through a
separate gill slit
 The 1st pair of gill slits is modified into spiracles- a pair of
round openings just behind each eye, located on the
dorsal surface of skates and rays
 Bony fishes: gills on each side share a common gill
chamber that opens to the outside, each opening is
covered by an operculum, when the mouth opens the
opercula close and the pharynx expands, sucking water in.
when the mouth this process is in reverse
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Gill arches support the gills and each
arch has 2 rows of fleshy projections
called gill filaments,
› Have a red ish color
› Each gill filaments have many rows of thin
plates called lamellae (they contain
capillaries)
 Surface area
Diffusion will only happen if oxygen is more
concentrated in the water than in the blood
 countercurrent system of flow- the blood in
the gills flows the opposite way as the water
 once the oxygen has entered the blood it is
carried through the body by hemoglobin,
which is a red protein. It is contained in
erythrocytes
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› Muscles also have myoglobin which is similar to
hemoglobin.
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Blood of bony fishes less salty than
› Lose water by osmosis, “drink” a lot of water.
 Salt is extracted by kidneys and chloride cells in the
gills. Small concentrated amounts of urine.
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Cartilaginous fishes making their blood
concentration closer to the
concentration of seawater.
› Retain a chemical called urea, amount in
blood is controlled by the kidneys.
› “drink” water
› Salts are excreted by kidneys, intestines and
special gland near anus called rectal gland.
 Vertebrates
have most complicated
and advanced nervous systems
› Central nervous system, brain and spinal chord
 coordinates body activities and stores
information.
› Olfactory sacs, on both sides of the head,
used to smell,
 Each sac opens to the outside through 1 or 2
openings (nares)
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Have LOTS of taste buds- located in their
mouth, lips, fins, and skin.
› Found on barbels in many bottom feeders.
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Eyes- focuses by moving closer or further
away from the subject
› bony fish depend more on eyesight than
cartilaginous fish.
 Bony fish have colored vision, cartilaginous fish
have none or vary little
 Some sharks have a nictating membrain
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Lateral line- detect vibrations in the water,
system of small canals that runs along head
and body, filled with sensory cells
(neuromasts) that are sensitive to vibrations.
 Cartilaginous fishes have ampullae of Lorenzini that
can detect weak magnetic electrical fields.
Fish also have inner ears- paired hearing organs
located to the sides of the brain, just besides the
eyes.
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Set of fluid filled canals that contain sensory
The swim bladder can amplify sound.
Gives equilibrium and balance.
Detect changes in body position from movement of
calcareous ear stones or otoliths that rest on sensory
hairs