Class Agnatha
•80 species of hagfishes and lampreys
•Skin lacks scales and plates
•Cartilaginous skeleton, unpaired fins
•Notochord remains throughout life
•Some are parasitic
•Hagfishes are marine; most lampreys
live permanently in fresh water
•All lampreys reproduce in fresh water
Figure 34.8 A hagfish
Figure 34.9 A sea lamprey
Class Chondrichthyes
Includes:
Sharks
Rays
Skates
Figure 34.11 Cartilaginous fishes (class Chondrichthyes): Great white shark (top
left), silky shark (top right), southern stingray (bottom left), blue spotted stingray
(bottom right)
Class Chondrichthyes
•Skeletons are made of cartilage
•Skin is covered with placoid
scales
Sharks
•Mouth contains 6-20 rows of
teeth that point inward; when they break or wear
down, the others move forward
•Paired nostrils on the snout have specialized nerve
cells that connect
with olfactory bulbs of the brain
•Largest brain of all fish
Adaptations of Cartilaginous Fish
•Most pump water over their gills
by expanding and contracting their mouth cavity
and pharynx
•Rays and skates have spiracles
located behind their eyes
•Ammonia is converted to urea, which is much
less toxic
•Swimming generates lift and
many cartilaginous fish can store large amounts
of low-density lipids in their livers to maintain
buoyancy
Reproduction in Chondrichthyes
Fertilization is internal, a male transfers sperm using a
modified pelvic fin called a clasper.
Sensory Functions
•The lateral line system is present in
nearly all fish, which is a row of sensory structures that
runs the length of the fish to detect vibrations in the
water
Class Osteichthyes – Bony Fish
Characteristics:
•Bones
•Lungs or Swim Bladder
Lungfishes have gills and
lungs
** All bony fish have an operculum
a hard plate that opens at the rear
and covers and protects the gills
•Scales
Lobe-Finned Fishes
•Have fleshy fins that are supported by a
series of bones
•7 species of lungfishes and one species of
coelocanth exist today
• The lungfish
resembles a short
bodied eel. The
base color of the
fish is brown with
small spots all
over.
• They are
carnivores. The
dorsal and anal
fins are longbased.
Figure 34.14 A coelocanth (Latimeria), the only extant lobe-finned genus
Ray-Finned Fishes
•Have fins that are supported
by long, segmented, flexible
bony elements called rays.
•includes eels, perch, salmon,
guppies, bass
Figure 34.13 Anatomy of a trout, a representative ray-finned fish
Figure 34.12a Ray-finned fishes (class Actinopterygii): yellow perch
Respiratory and Circulatory Systems
•Water flows away from the head and
the blood flows toward the head. This countercurrent
flow allows more oxygen to diffuse into the gills
•Fish regulate their overall density by adjusting the
amount of gas in their swim bladders
•There are four chambers in the heart
Buoyancy in Fish
Squalene (liver oil)
Buoyancy in Fish
Buoyancy in Fish
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Respiration in Fish
Respiration in Fish
Osmoregulation in Fish
Reproduction
•Fertilization in most species is external
•If internal fertilization occurs, the male
inserts his sperm into the female using
a modified anal fin; the female carries
the eggs inside her until the young are
born
Fish Reproductive Adaptations
Diadromous - fish that make “two runs”
in their life to live and reproduce
Anadromous - fish that “run up” - salmon
Catadromous - fish that “run down” - eels
Parthenogenesis - no males required,
females produce diploid eggs - Amazon
molly