Transcript Class osteichthyes Bony Fish

What is a Fish?
• ___________________
• Live in water
– 40% are freshwater
– 60% are marine
• Gills for breathing
• ___________________
• ___________________
Important Terms
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Ventral – bottom side
___________________– back side
Anterior – front end (head)
___________________– tail end
Fish Fins
• Caudal fin – ___________________ – forward
movement (in most)
– Heterocercal – upper lobe is longer than lower lobe
– Homocercal – upper and lower lobes are same size
• Dorsal Fin – ___________and stability
– Can have 1-3 dorsal fins
• Pectoral Fin – dynamic lift, “walking”,
___________________
– Forward movement in rays and skates
• Pelvic Fin – up/down movement, steering,
___________________
• Anal Fin – ___________________ and stability
Heterocercal Tail
Homocercal Tail
Fish Fins
Fish Fins – Sharks
Evolution
• The first fishes probably evolved in the ocean
around ___________________ million years ago.
• First fish are thought to be jawless, but did have
a digestive system and a chordate body plan.
• Early jawed fishes were far more successful at
eating invertebrates with shells or exoskeletons.
• These jawed fish were also equipped with paired
___________________ to stabilize movements
Evolution
• The numbers and types of jawed fishes increased
dramatically beginning about 410 million years ago.
• By the end of the Devonian period (aka the Age of the
Fishes), from 408 to 360 mya, jawed fishes had spread
into a vast number of ___________________
• The ancestral jawed fishes gave rise to cartilaginous
fishes and ___________________ fish.
Hagfish and Lampreys
CLASS AGNATHA
Class Agnatha
• ___________________(“A” = lacking, “gnathos” =
jaw)
• No paired appendages to aid in locomotion
• Gill slits
• Some have openings called ___________________
glands
• Round, sucking mouth surrounded by organs
sensitive to touch and smell.
• Degenerative eyes covered by a thick skin
• Body ends in a flattened ___________________
movement)
Sharks, Skates, Rays, and Ratfish
CLASS CHONDRICHTHYES
Chondrichthyes Basics
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“Chondros” = cartilage, “ichtyhs” = fish
Includes sharks, skates, rays, and ratfish
Skeleton is made of ___________________
Rough skin covered by placoid scales
Jaws with teeth
Paired lateral ___________________
Often active lifestyles
Sharks
• 350 species
• Nearly all are marine
• No gas ___________________ – will sink if
they stop swimming
• ___________________ (spindle shaped) –
hydrodynamic
• Caudal fin is well developed and powerful –
usually ___________________
• Usually two dorsal fins, first of which is
typically larger and triangular
• ___________________ gill slits
Sharks - Teeth
• Powerful jaws have rows of numerous sharp
___________________
• Lost or broken teeth are replaced by another, which
slowly shifts forward from the row behind it as if on a
conveyor belt
• Can have between 5 and 15 rows of teeth
• Some sharks are thought to go through 12000 50000 teeth in a ___________________
– Tiger sharks – 24000 teeth in a 10 year period
Sharks
• Sharks are in danger!
• Hunted for ___________________ , oil, skin
(leather, sandpaper), ___________________
(soup), cartilage (“joint nutrient”)
• US has a ban on shark finning
• Many countries have strict laws and regulations
pertaining to shark ___________________
Rays and Skates
• Approx 500 species
• Dorsoventrally flattened bodies
• Live on the ocean bottom for the most part –
called ___________________
• ___________________ of gill slits on the
ventral side
• Pectoral fins are flat and greatly expanded and
fused to the head
• ___________________ usually on top of head
Rays
• Stingrays, eagle, bat, manta, and cow-nosed rays
• Whip-like tail usually equipped with stinging
___________________ at the base for defense
– Some are poisonous
• Many bury themselves in the
___________________ , making them almost
invisible
• Feed on clams, crabs, small fish, and other small
animals that live in the sediments
– Teeth are modified into grinding plates that can crush
___________________
• Give birth to live young
Electric Rays
• Have specialized organs that produce
___________________ on each side of the head
• Can deliver shocks up to 200 volts that stun the
fishes they eat and discourage predators
Skates
• Lack a whip-like tail and stinging spines
• Some have electric organs
• Lay egg ___________________
Ratfish – aka Chimaeras
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About 30 species
Mostly found in ___________________ water
One pair of gill slits covered by a flap of skin
Some have a long rat-like tail
Feed on bottom-dwelling crustaceans and
___________________
Bony Fish
CLASS
OSTEICHTHYES
Class Osteichthyes – Bony Fish
• 23,000 species – 96% of all fishes and almost half of
all ___________________
– 75 – 100 new species are discovered every year!
• Skeleton made at least partially of
___________________
• Cycloid or ctenoid ___________________ , or no
scales at all
– Cycloid scales are smooth
– Ctenoid scales have many tiny spines along their exposed
borders
• The scales are made of bone and are covered by a
thin layer of skin as well as a protective
___________________
Scale
Types
Ctenoid Scales –
See the tiny little spines?
Placoid Scales –
Found in Sharks
Cycloid Scales
Osteichthyes Characteristics
• Operculum, or gill cover – flap of bony plates and
tissue that protects the ___________________
• ___________________ tail
• Fins generally consist of thin membranes that are
supported by bony spines, or fin rays
• Fin rays may consist of rigid spines that act as
rudders or are used for ___________________;
some are flexible and used for propulsion and
added maneuverability
Osteichthyes Characteristics
• ___________________ is typically located on the
anterior end (head)
• Jaws have much more freedom of movement
– Protrusible because they can be projected outward
from the mouth
• Teeth are generally attached to the jawbones
• Most have a swim ___________________ , a
gas-filled sac just above the stomach and
intestine
– Allows the fish to adjust buoyancy
– Significant development that compensates for the
relatively ___________________ bony skeleton
Physiology
BIOLOGY OF FISH
Biology of Fishes
• Ichthyology – the scientific study of
___________________
• Fishes are extraordinarily diverse in shape, size,
color, feeding habits, reproductive patterns, and
behavior.
• They have adapted to nearly every type of marine
environment and all land ___________________
evolved from them.
• For cartilaginous and bony fish, we will look at:
*Body Shape
*Coloration *Locomotion
*Feeding
*Digestion *Circulatory System
*Respiratory System
*Behavior
*Regulation of Internal Environment
*Nervous System and Sensory Organs
*Reproduction and Life History
Body Shape
• Streamlined body – ___________________
swimmers – helps move through water
• Laterally compressed body – good for leisurely
swimming around coral reefs, kelp beds, or rocky
reefs, but are still efficient enough to allow for
bursts of speed to escape ___________________ or
capture prey
• Dorsoventrally flattened body – adapted for life on
the ___________________
• Laterally flattened – also adapted for life on the
___________________ – begin life with one eye on
each side of head, but as they develop one eye
migrates up to lie next to the other one
• Elongated bodies – allow for shelter in small, narrow
spaces in rocks or ___________________
Coloration –Chromatophores
• Tropical bony fish tend to be brightly colored
• Chromatophores – special skin cells that contain
colored ___________________
• The amazing variety of colors and hues observed
among marine fishes results from combinations
of chromatophores with varying
___________________ of different pigments
• Many fishes can rapidly change color by
contracting and ___________________ the
pigment in the chromatophores.
Coloration
• Fishes may also have structural colors that result
when a special surface reflects only certain colors of
light.
– Most are the consequence of ___________________ that
act like tiny mirrors
– The crystals are contained in iridophores
Coloration
• Fish can change colors for:
– ___________________
– Reproductive condition
– Warning coloration – advertise danger, poison, or bad
taste
– Cryptic coloration – ___________________ to
deceive predators or prey
– Disruptive coloration – the presence of color stripes,
bars, or spots that help break up the outline of a fish
– ___________________ predator
• Color changes are common among coral reef
fishes!
Coloration - Countershading
• Open-water fishes and many shallow-water
predators are rarely colorful.
• Most have ___________________ – silver/white
ventral side, dark dorsal side
– Form of ___________________ in open waters
• Deep-water fishes tend to be black or red, both
of which are hard to see in the ocean depths.
Locomotion
• Fishes swim to obtain ___________________,
escape from predators, find mates, and, for
some, swimming flushes gills with water to
obtain oxygen.
• Most fishes swim with a rhythmic side-to-side
motion of the body or ___________________
• S-shaped waves of contractions moving from
head to tail push against the water and force the
body forward.
– Rhythmic contractions are produced by bands of
muscles called ___________________, which run
along the sides of the body.
Feeding – Cartilaginous Fish
• Most sharks are ___________________ !
• However, several species of cartilaginous fishes are
filter feeders – whale shark, basking shark, manta
and devil rays.
• Filter-feeding fish filter the ___________________
with their gill rakers, slender projections on the
inner surface of the gill arches.
• The width of space between the gill rakers
determines the size of food captured.
• Water is strained through the gill
___________________, and the fish swallows the
food that is left behind.
Feeding – Bony Fish
• Bony fish are very diverse when it comes to feeding
methods.
• Most are ___________________
• Capture their prey from sediments, the water
column, the surface of rocks, or from other
organisms, including other fishes.
• Some ___________________ their prey, others sit
and wait.
• Carnivorous bony fishes typically have welldeveloped ___________________ for catching,
grasping, and holding their prey which is usually
swallowed whole.
Feeding – Bony Fish
• ___________________– feed primarily on
seaweeds and plants
• Filter feeders – filter ___________________
using gill rakers.
– usually found in large schools
• Plankton feeders are the most abundant fishes in
the ocean
– Important food source for many types of
___________________
Digestion
• Pathway of food:
– swallow  pharynx  esophagus 
___________________ (digestion starts here) 
intestines  cloaca
• In bony fish, enzymes are realeased by:
– Pyloric caeca (anterior portion of intestine)
– ___________________
– Inner wall of intestines
• The liver is also important because it secretes bile
which is needed for the breakdown of fats.
– The liver is particularly large and oil-rich in sharks,
sometimes making up as much of
___________________ of their body weight.
– The liver also plays a huge role in detoxifying the
___________________ in all ___________________
Digestion - Intestines
• Carnivorous fishes have short, straight intestines.
• Herbivorous fishes have ___________________
intestines
• Many cartilaginous fish contain a spiraling portion
of the intestine called the spiral valve
– ___________________ the internal surface area
• The intestine is responsible for absorbing the
nutrients
– Nutrients pass into the ___________________ to be
distributed through the body.
• Undigested material exits through the anus, or
the ___________________ , the common
passage for the digestive, excretory, and
reproductive systems in cartilaginous fishes.
Circulatory System
• All fishes have a two-chambered
___________________ that is located below
the gills.
• Pathway of blood:
– Veins  1st chamber of heart  2nd chamber of
heart  ___________________  arteries 
capillaries  veins
• Gas exchange takes place in the gills
– Blood picks up ___________________ and
releases carbon dioxide
Respiratory System –
Cartilaginous Fish
• Irrigation of the Gills – Cartilaginous Fish
– ___________________ , plus the opening and closing
of the mouth, forces water through the mouth, over
the gills, and out through the gill slits.
– The first pair of gill slits of cartilaginous fishes is
modified into ___________________ (round
openings behind the eyes)
– Spiracles allow intake of ___________________ even
when the ventral mouth is buried in the sediments.
Respiratory System – Bony Fish
• Irrigation of the Gills – Bony Fish
– Bony fish have a more efficient mechanism.
– The gills on each side share a common gill
___________________ , which opens to the outside
through an opening on each side of the head.
– Each opening is covered by an
___________________
– When the mouth opens, the opercula close and the
pharynx expands, sucking water in.
– The opposite happens to pump the
___________________ out.
Respiratory System – Structure of the Gills
• Gills are supported by cartilaginous or bony structures,
called gill ___________________
• Each gill arch bears two rows of slender fleshy projections
called gill filaments.
• Gill rakers project along the inner surface of the gill arch
that prevent food particles from entering and injuring the
gill filaments or may even be specialized for filtering the
___________________ in filter-feeding fishes.
• The gill filaments have a rich supply of capillaries that
contain oxygen-rich blood, which gives gills their bright
___________________ color.
• Each gill filament contains many rows of thin plates called
lamellae, which also contain capillaries.
• Lamellae greatly ___________________ the surface area
through which gas exchange can take place.
Respiratory System – Gas Exchange
• Oxygen dissolved in the water diffuses into the
capillaries of the gill filaments to oxygenate
___________________
• Diffusion will take place only if oxygen is
___________________ concentrated in the water
than in the blood.
• As oxygen diffuses from the water to blood in the
capillaries, the amount of ___________________ in
the water decreases and that in the blood increases.
• Fishes have evolved an adaptation called a
countercurrent system of flow to
___________________ the efficiency of gas
exchange.
– The blood in the gills flows in the opposite direction to
the water passing over them.
Respiratory System – Gas Exchange
• The blood disposes of its carbon dioxide using the
same mechanism. Blood flowing into the gills from
the body has a high concentration of carbon dioxide,
while the water has a low concentration  The
carbon dioxide diffuses out of the
___________________ and into the water
• Once oxygen enters the blood it is carried through
the body by ___________________ , a red protein
that gives bloods its color.
• Hemoglobin carries oxygen to the tissues as it is
needed and picks up the carbon dioxide and takes it
to the gills.
• Muscles use a lot of oxygen during exertion so they
need to be able to store excess oxygen. Muscles
have a protein called ___________________
Regulation of the Internal Environment –
Bony fish
• The blood of marine bony fishes is less
___________________ than seawater.
• As a result they lose water by __________________
• Marine bony fishes therefore need to osmoregulate
to prevent dehydration.
• To replace lost water, they swallow seawater, which
contains excess salts, some of which pass straight
through the gut without being absorbed.
• Salts that are absorbed are excreted by the kidneys
(the most important excretory organs of
vertebrates) and specialized ___________________
cells in the gills.
• The ___________________ conserve water by
producing only small amounts of urine.
Regulation of the Internal Environment –
Cartilaginous fish
• Cartilaginous fish reduce ___________________ by
increasing the amount of dissolved molecules, or
solutes, in their blood, making the blood
concentration closer to that of seawater.
• They retain a chemical called urea, a waste product
that results from the breakdown of proteins.
• The amount of urea in the blood is controlled by the
___________________
• Cartilaginous fish also absorb water to prevent
___________________ , mostly through the gills
and from food.
• Excess salts are excreted by the
___________________ , intestine, and a special
gland near the anus called the rectal gland.
The Central Nervous System – In General
• Vertebrates have the most ___________________
and advanced nervous system of any animal group.
• At the heart of the nervous system is the central
nervous system (CNS), consisting of the
___________________ and spinal cord.
• The CNS coordinates and integrates all body
activities and stores information.
• The brain is divided into several regions each having
a particular function.
• The brain is protected by a cartilaginous or bony
skull and is connected to the rest of the body by
___________________
Can Fish Smell?
• Most fishes have a highly developed sense of
___________________ , which they use to detect
food, mates, and predators, and sometimes to find
their way home.
• Fishes do this with a special sensory cells located in
olfactory sacs on both sides of the head.
• Each sac opens to the outside through one or two
openings, the nostrils, or ___________________
• Sense of smell is well developed in
___________________ – They can detect blood in
concentrations as low as fractions of one part per
million!!!
Do fish have the ability to taste?
• Fishes detect some chemical stimuli with taste
buds located in the mouth and on the
___________________ , fins, and skin.
• Taste buds are also found on ________________,
whisker-like organs near the mouth of many
bottom feeders, such as marine catfishes.
How Do Fish See?
• Fishes have eyes that only
___________________ as they move closer and
further away from an object
– Most vertebrates change the shape of the lens to
focus!
• Bony fish rely on ___________________ more
than cartilaginous fish.
• Some sharks have a distinct
___________________ membrane that can be
drawn across the eye to reduce brightness and to
protect the eye during feeding.
The Lateral Line
• Fishes have a unique sense organ called a lateral line
that enables them to detect ___________________
in the water.
• It consists of a system of small canals that run along
the head and body.
• The canals lie in the skin and in the bone or cartilage
of the ___________________
• The canals are lined with clusters of sensory cells, or
neuromasts, that are sensitive to
___________________
• The lateral line picks up vibrations from the
swimming of other animals and from sound waves.
• This allows fish to avoid ___________________,
detect prey, orient to currents, and travel in a
___________________
Ampullae de Lorenzini
• Cartilaginous fish have sense organs in the head called
ampullae de Lorenzini that can detect weak
___________________ fields.
• Helps the fish detect and ___________________ prey
• Also thought to help in ___________________ used as
a sort of compass) and possibly even to detect currents.
The Inner Ears
• Fishes can perceive sound with inner ears, paired
hearing organs located to the sides of the brain just
behind the ___________________
• In some fishes the swim bladder amplifies the sound
by vibrating and transmitting sound waves to the
inner ear.
• Also involved in equilibrium and
___________________
• Many fishes detect changes in body
___________________ from movement of
calcareous ear stones, or otoliths, that rest on
sensory hairs, a mechanism similar to the statocytes
in invertebrates.
Behaviors
• Nearly all aspects of the lives of fishes involve
complex behavior to ___________________ to
light and currents, to find food and shelter, and
avoid predators.
• Behavior is also an important part of fish
___________________ and reproduction.
• In this section we will look at behaviors
pertaining to:
– Territoriality
– Schooling
– Migrations
Behavior: Territoriality
• Some fishes are known to establish _____________,
home areas that they defend against intruders.
• Some defend territories only during reproduction
while others defend their territory permanently
because they may use it for food and
___________________
• Territoriality is most common in
___________________ areas like coral reefs and kelp
Damselfish are particularly
beds.
nasty when it comes to
defending their territory.
Sometimes they attach
individuals much larger than
themselves, including divers!
Behavior: Territoriality
• Fishes use a variety of ___________________
behaviors to defend the territories.
• Its rare that a fish fight will actually break out – its
more of a bluffing game!
• Fishes have threatening ___________________ –
raised fins, an open mouth, and rapid darting about
are examples
• Other fish (mainly bony fish) make threatening
___________________ – grinding their teeth,
rubbing bones, or rubbing fin spines on other bones
• Some fishes “drum” by pulling muscles on the swim
bladder, and this sound is amplified by the air-filled
___________________
Behavior: Schooling
• Many fishes from well-defined groups, or
___________________
• It has been estimated that around 4,000 species,
both marine and freshwater, school as adults.
– Includes herrings, sardines, mullets, and some mackerels.
– Some cartilaginous fish school too – hammerheads and
manta rays
• Schools function as well coordinated units, though
they appear to have no ___________________
• The individual fishes tend to keep a constant
distance between themselves, turning, stopping,
and starting in near perfect ___________________
• Fish can use ___________________ , the lateral line,
olfaction, and sound to keep track of each other.
Behavior: Why Do Fishes School?
• Schooling offers ___________________ against
predation.
– Predators may be confused if the school circles or splits
up.
– It also makes it tough for predators to focus on one fish if
the school is shifting, and darting.
• Schooling increases the swimming efficiency of the
fish because the fish in front form an eddy that
reduces water ___________________ for those
behind.
• Schooling can also be advantageous in feeding or
___________________
• However, reasons probably vary from species to
species and may occur for multiple reasons.
Behavior: Migrations
• Another interesting behavior of marine fishes is
___________________, regular mass movements
from one place to another once a day, once a year,
or once in a lifetime.
• Schools can migrate onshore and offshore to
___________________
• Many open-water fishes migrate several hundred
meters up and down the water column every day to
feed.
• Other fishes make transoceanic migrations – tunas,
salmons, etc.
• ___________________ is usually the main reason
for migration.
Behavior: Migrations
• However, some migrations take place for
___________________ purposes.
• Some fishes migrate between sea and fresh water
for reproduction.
• Anadromous fishes spend most of their lives at sea
but migrate to ___________________ to breed.
– Examples: Sturgeons, lampreys, smelts, and salmon
• Catadromous fishes have a migratory pattern
opposite that of salmon – the breed at sea and then
migrate into ___________________ to grow and
mature.
– Examples – at least 16 species of eels
Salmon
• After several years at sea,
salmon mature sexually and
start migrating into rivers.
• Salmon find their home streams
with remarkable accuracy, using
a type of chemical
___________________
• They recognize the “smell” of
their home stream, along with
the “smells” of all the other
streams on their way.
• The ability to find their way
back to their home area is
called ___________________
behavior.
Reproductive System
• The sexes of fish are usually separate with both sexes
having paired ___________________ located in the body
cavity.
• In cartilaginous fishes, ducts lead from the ovaries and
testes into the ___________________, which opens to the
outside.
• Jawless and bony fishes have a separate opening for urine
and gametes, the urogenital opening, which is located just
behind the ___________________
• In many marine fishes the gonads produce gametes only
at certain times. The timing of this production is crucial –
Both sexes must be ready to ___________________ at the
same time.
• Spawning, as well as larval development, must take place
during the period with the most ___________________
conditions.
Reproductive System – Sex hormones
• The timing of reproduction is controlled mostly
by sex ___________________, which are
produced in the gonads and released in small
amounts into the blood.
• Sex hormones stimulate the maturation of
___________________ and may cause changes
in color, shape, and behavior before breeding.
• The release of these hormones is triggered by
environmental factors such as day length,
temperature, and the availability of
___________________
Reproductive System - Hermaphrodites
• A few marine fishes are ___________________
• Some are called simultaneous hermaphrodites
because they can produce sperm and eggs at the
same ___________________
– They are able to fertilize their own eggs. However,
they usually breed with one or more other individuals.
• Hermaphroditism is found more commonly
among ___________________ fishes, an
adaptation to the depths of the ocean where it
may be difficult to find members of the opposite
sex.
Reproductive System - Hermaphrodites
• Another variation of hermaphroditism is called
sex ___________________, or sequential
hermaphroditism.
– In this case, individuals begin life as males, but
change into ___________________ (protandry), or
females change into males (protogyny)
– These changes are controlled by sex hormones but
triggered by social cues such as the
___________________ of a dominant male.
– Commonly occurs in sea basses, groupers,
parrotfishes, and wrasses.
Reproductive Behaviors
• Many species ___________________ and congregate in
specific breeding grounds.
• Many bony fishes change ___________________ to
advertise their readiness to breed.
• Other physical changes may occur during mating season.
– Male sockeyes jaws grow into vicious-looking hooks
– Male salmon develop a large hump
• The first step in reproduction is ___________________, a
series of behaviors that serve to attract mates.
– May involve an exchange of active displays such as “dances,”
special postures that display colors, and swimming upside
down.
• Each species is unique in its courtship behaviors – prevents
breeding between two ___________________ species.
Reproduction – Internal Fertilization
• Some fishes have ___________________
fertilization of the eggs, in which the sperm is
directly transferred from males to females
through the act of copulation.
• Internal fertilization occurs mainly is
___________________ fishes.
• Not much is known about internal fertilization
and the sex life of these fishes.
• Male sharks, rays, and skates have a pair of
copulatory organs called ___________________
located along the inner edge of the pelvic fins.
Claspers are inserted into the female’s cloaca.
Reproduction – External Fertilization
• External fertilization, the release of ___________________ into
the water, or broadcast spawning, is more common in fishes.
• Open-water fishes and those living around coral reefs and other
inshore environments ___________________ directly into the
water after courtship.
• Females typically release many eggs
– Atlantic Cod – 1 m long female can release up to 5 million eggs
– Atlantic Tarpon – releases more than 100 million eggs every time it
spawns.
• Some eggs fertilized in the water column drift in currents and
develop as part of the ___________________ Others eggs sink to
the bottom. Other fish deposit their eggs on the surface of sea
grasses, sea weeds, and rocks. Others bury their
___________________
Reproduction – External Fertilization
• Most of the eggs that are released into the
___________________ don’t survive.
• Fishes that release eggs release as many as possible to ensure
that at least a few survive and make it to adulthood.
• Eggs require a lot of ___________________ to produce because
they must contain enough yolk to nourish the young until they
hatch and can feed.
Damselfish Eggs
Do Any Fish Actually Take Care Of Their
Eggs?
• Fishes that ___________________ fewer and larger
eggs have evolved ways to take care of them.
• Damselfish – Males establish and defend breeding
sites or ___________________ in holes among rocks
or coral, empty mollusc shells, an other shelters.
• Others that ___________________ are gobies,
blennies, and scuplins.
• Antarctic Plunderfish – the female prepares a
breeding site and guards it for four to five months
after ___________________ . If she disappears or is
removed, her job is taken over by a male.
Do Any Fish Actually Take Care Of Their
Eggs?
• Some fishes even carry their eggs after they have
been ___________________
• Male pipefishes carry the eggs attached in neat
rows to their ___________________
• A male seahorse literally becomes pregnant after
the female deposits eggs in a special pouch on
his belly!
• In some cardinalfishes, marine catfishes, and
other groups, males carry the fertilized eggs in
their ___________________
Early Development – Oviparous Fish
• Most fishes spawn eggs and are known as
___________________
– The embryo is enclosed by a large, leathery egg case that
drops to the bottom after spawning.
– Some sharks, skates, and other cartilaginous fish are
oviparous – about 43%
– The egg cases are rather large and often have thin
extensions that attach them to ___________________
– The eggs have a large amount of yolk in a yolk sac that is
attached to the embryo’s belly. Yolk provides
___________________ for several months of
development.
– Results in a well developed ___________________ when
the egg finally hatches.
Early Development - Ovoviviparous
• In ovoviviparous fish, the female retains the eggs
inside her reproductive tract for additional
___________________
– The eggs develop inside the female, which gives birth to
___________________ young.
– Most of these fish are cartilaginous, with only a few being
bony fish.
– In some sharks, the embryos rely on other sources of
___________________ once they have consumed the
yolk.
– Sandtiger shark – Only two pups, which are large (1 m)
and active, are born. Each survived in one of the two
branches of its mother’s reproductive tract by
___________________ its brothers and sisters.
Early Development - Viviparous
• In viviparous fish, embryos actually absorb
___________________ from the walls of the
mother’s reproductive tract.
– This is very similar to the development of the embryo
in ___________________
– Includes some sharks and rays. A few bony fish are
also included.
– These fish bear ___________________ young that
got their nutrition for development from direct
contact with the reproductive tract of the mother.
– The young have large fins that absorb nutrients from
the walls of the mother’s ___________________
Early Development – Bony Fish
• Development of the embryo proceeds rather quickly
in most bony fishes.
• The transparent outer envelope of the eggs, the
chorion, in thin, allowing ___________________ to
diffuse through.
• The embryo is supplied with nutrient-rich yolk.
• After one or more days of development, the eggs
___________________ into free-swimming larvae,
or fry.
• When they first hatch, the larvae still carry the yolk
in a yolk sac.
• The yolk is eventually consumed, and the larvae
begin ___________________