Download Fish Lecture - Jutzi

Fish
Class Agnatha,
Chondrichthyes, &
Osteichthyes
Subphylum Vertebrata
● All vertebrates are divided into
two Superclasses
● Superclass Agnatha - Jawless
vertebrates (2 living species)
● Superclass Gnathostomata Jawed vertebrates (all other
vertebrates)
Vertebrate Reproduction
● Oviparous
○ Lay eggs outside the body
so they may develop and
hatch
● Ovoviviparous
○ Egg remains in mother until
offspring hatch
○ The offspring are born alive
● Viviparous
○ Embryo receives
nourishment from mother
○ The offspring are born alive
Early Amphibian
(Ancestor of all Tetrapods)
Lungfish
Coelacanths
Ray-Finned Fish
Lobe-Finned Fish
Cartilaginous Fish
Bony Fish
Hagfish & Lampreys
Placoderms
Ostracoderms
Superclass Agnatha
● First appeared in the Cambrian
Period about 500 mya
● No jaws
● No paired appendages
● Notochord provides primary
protection and support for
nerve cord
● Fertilization & development
are carried out externally
Ostracoderms
● Earliest vertebrates
● Evolved just after the
Cambrian explosion
● Jawless - fed by filter
feeding
● Covered in armor made of
bony plates
● Totally extinct group of fish
(P-T extinction)
Hagfish and Lampreys
Lampreys
● Live mostly in coastal and
fresh waters
● Always return to freshwater
to reproduce
● Though jawless, the mouth
is lined with sharp teeth
able to tear flesh
● Ectoparasitic
Lampreys
● Begin life as burrowing,
toothless larvae
● After 5 to 7 years, they
undergo an incredible
metamorphosis to turn into
pelagic, adult parasites
● Attach to fish, secrete an
anticoagulant, and feed on
blood
Hagfish
● Jaw is partially movable
horizontally, but still
considered Agnathans
● Entirely marine - never
found in freshwater
● Able to change sex to meet
population needs - many
species exist in a 100:1
female-to-male ratio
● No larval stage
Hagfish
● Able to secrete copious
amounts of thick slime to
deter or evade predation
● Clean off the slime by tying
themselves in knots
● Endoparasites - feed by
burrowing into the mouth,
gills, or anus of a host fish
and consuming their prey
from the inside out
Superclass Gnathostomata
● Jaws
● Paired appendages
Early Amphibian
(Ancestor of all Tetrapods)
Lungfish
Coelacanths
Ray-Finned Fish
Lobe-Finned Fish
Cartilaginous Fish
Bony Fish
Hagfish & Lampreys
Placoderms
Ostracoderms
Class Placodermi
● Among the first jawed fish
along with the ancestors of
Class Chondrichthyes
● Went extinct along with the
Ostracoderms
● Head and thorax were
covered by bony plates
● 320 mya fossil shows
earliest example of
viviparous birth
Class Chondrichthyes
● Cartilaginous skeleton
● Notochord provides a large
portion of back support
● No operculum
○ Must swim constantly
to allow oxygenated
water to move across
gills
● No swim bladder
○ They are unable to
regulate their buoyancy
levels
Buoyancy
● Cartilaginous fish must also
constantly swim to keep from
sinking. They use dynamic lift
to maintain a constant level
in the water column
● Liver oil and the ability of
some sharks to swallow air
allow them to obtain some
level of buoyancy
Class Chondrichthyes
● Respire with the use of 5 to
7 exposed gill slits
● Skin covered with dermal
denticles - tooth-like
structures that protect the
skin and cause it to feel like
sandpaper when rubbed
against the grain
● Denticles also reduce small
vortices produced during
movement that cause
hydrodynamic drag increase swimming
efficiency
Sharks
● The largest of all fish is the
whale shark. It is a filter
feeder
● Most sharks are simple
carnivores
● Teeth are anchored into
flesh rather than bone and
they rip out and are
replaced very rapidly
Shark Anatomy
Sexual Dimorphism in Sharks
Sharks
● Although most fish are
exothermic, the shortfin
mako shark and the great
white shark are slightly
endothermic
● Most sharks are
ovoviviparous. They carry
their eggs internally until the
young hatch and are born
alive and fully functional
Sharks
● Sharks have
electroreceptor organs
called the Ampullae of
Lorenzini that detect the
electromagnetic fields
that all living things
produce. This assists
sharks in hunting and in
navigation
● Sharks also have a very
keen sense of smell and
can detect 1:1,000,000
blood in water
Skates & Rays
Skates & Rays
● Possess 5 gill slits that are
located underneath the
pectoral fins rather than on
the side of the head as in
sharks
● Eggs laid in little pouches
you may find on the beach
Skates & Rays
● Wide distribution of group
members. Tropical to coldwater species exist
● Most are benthic (live on the
seafloor) and respire by
moving water in through
their spiracles towards their
gills
● Manta ray is an example of a
rare pelagic ray
Skates & Rays
·Skates and rays are very similar. However, skates tend to have a
more shovel-shaped head than rays and they lack spines in their tails.
Early Amphibian
(Ancestor of all Tetrapods)
Lungfish
Coelacanths
Ray-Finned Fish
Lobe-Finned Fish
Cartilaginous Fish
Bony Fish
Hagfish & Lampreys
Placoderms
Ostracoderms
Class Osteichthyes
● Boney fish - Actually called
endochondral bone because it
is formed by the ossification of
cartilage
● Comprise the most various and
largest class of vertebrates on
Earth today
● Includes the vast majority of all
fish
Class Osteichthyes
● Swim bladder present Allows a fish to adjust its
buoyancy and thus its
position in the water
column
● Operculum present - Allows
fish to pump water across
the gills without having to
physically move through the
water
● Lateral line – senses
vibrations in the water
Oxygen Exchange at the Gills
Countercurrent Exchange
Osteichthyes Evolution
Osteichthyes Classification
Subclass Actinopterygii
● Ray-finned fish
● Comprised of most
members of class
Osteichthyes
● Fins attach to body of
the fish with multiple,
small bones
● All members have
homocercal tails
Caudal Fins
General Osteichthyes Anatomy
Subclass Actinopterygii
● Bichirs
● Also known as ropefish
● Live in freshwater
environments in Africa
and around the Nile delta
● Identified by noting the
unique 12+ dorsal fins
● Sister group of all other
ray-finned fish
Subclass Actinopterygii
● Sturgeon & Paddlefish
● The most ancient living bony
fish with shark-like
heterocercal tails & partially
cartilaginous skeletons
● Sturgeons lack normal scales
seen on other bony fish but
they have armor plates along
their sides
● Paddlefish lack the armor
plating but have paddle-like
rostrums the detect
electromagnetic fields
Subclass Actinopterygii
● Gar
● Fresh, brackish, & marine
fish of the Americas
● Almost as old and primitive
as the sturgeons &
paddlefish
● Thicker scales than other
bony fish but not as heavily
armored as the sturgeons
● Identifiable by noting the
long, skinny snout
Subclass Actinopterygii
● Bowfin
● Only a single surviving
species in this entire family
of fish is native to eastern
US & Canada
● Closest relative to the
teleost fish
● Known for their long dorsal
fins that cover most of their
back
● Considered a trash fish - not
very edible
Subclass Actinopterygii
● Teleost Fish
● The most advanced of all fish
● Almost 30,000 species - more
than all other vertebrate
species combined
● Almost any fish you can name
belongs to this group
● Extremely important as food
sources for humans and many
other animals
Subclass Sarcopterygii
● Lobed fins joined to the body
at a single bone
● Two dorsal fins with separate
bases and diphycercal caudal
fins
● There are only 8 living
species in this subclass
●
● These include lungfish and
coelacanths
Subclass Sarcopterygii
● Sauropterygians are able to
utilize a primitive lung to
breathe air when their ponds
dry out or the water becomes
anoxic
● Lungfish are known to use
their fleshy pectoral fins like
legs and crawl to new ponds
when their previous ponds dry
out
Structure of Lungs
● The Trachea leads
down to the lung
● Separates into two
bronchi leading to
each lung
● Tubing terminates
into little sacks called
ALVEOLI that allow
for gas exchange
Subclass Sarcopterygii
● ·The subclass split into two
main groups long ago with the
coelacanths staying in the
ocean and the lungfish &
tetrapodomorphs moving to
freshwater environments
● Tetrapodomorphs further
evolved into land vertebrates
Fish Scales
The End!