Fish Physiology
Fish external physiology
Mouth types:
Caudal tails
• Lunate, crecent
• Forked
• Truncated, rounded
• Heterocercal
• Eel-like
Teeth:
• NO teeth or tiny
“sandpaper” teeth =
swallow whole, teeth
just keep it in
• Flat blunt =crushing
something’s shell
• Sharp but broad teeth
= chipping things off
• Carnivore teeth = duh
• Feathery teeth =
filtering tiny
plankton/algae/etc
FISH SCALES – 3 main types
PLACOID
GANOID
Magnified !
CTENOID
FISH SCALES – 3 main types
• Ganoid – armor
• Ctenoid –more flexible,
less tough – the most
common type of scale
• Placoid – sharks have this,
it is actually like tiny teeth
poking out of the skin
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Touch
Similar to our senses
Taste
Sight
Smell
Hear
Sense movement of water (lateral line)
“electrical” (not all fish)
Magnetic fields (some fish,. And whales)
Special
Fish senses
Fish hearing
Smelling and sight
• Nostril = water flows through, it isn’t
connected to anything.
Fish eye lens
• Fish eyes are small.
• Mammal eye
Fish eye
Lateral Line Organ
• Senses
movement
Electrical sensing
EVERY MUSCLE PRODUCES A LITTLE
ELECTRICITY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Some fish can sense that!
Electrical sensing
Electricity production
EVERY MUSCLE PRODUCES A LITTLE
ELECTRICITY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
200 Volts
500 Volts
http://www.youtube.com/watch?v=y9wktSQdyaE&feature=related
TASTE
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You have taste buds, so do Fish
They work the same way,
But some fish’s taste buds are ALL OVER HIS FACE!!!
A catfish has 10 X as many taste buds on his face than
in his mouth.
Gills = get dissolved oxygen
Gills
Gill rakers
Gill rakers
Human lungs
• At best, you can
only take out 50%
of the oxygen in
the air.
Gills can take out nearly 90 % of
oxygen of water that flow over it.
Getting the fuel
eat
Stomach (food
normally taken whole)
LIver
pancreas
Pyloric caeca
blood
Fats, proteins, carbs,
All get broken down,
Goal = glucose
Gall bladder
Intestines
poop
Fish digestive system
Transporting the fuel and oxygen
to the muscles – fish have two
chambers, we have four
Fish heart and circulatory system
Do fish drink?
• Fresh water fish never need to drink
water, it soaks in all their cells all the time.
• Salt water fish have to replace water all
the time, so they drink A LOT! (and have
a specialized way to pump the salt back
out)
Swim bladder.. Where does the air
come from?
Three basic
reproductive/development
strategies:
• Egg layers – embryo nurtured by
Oviparous
a yolk, waste builds up in egg till
hatching
Ovoviparous
• Mixture of both – typically eggs
Viviparous
• Live birth – embryo nurtured by
held inside, till hatched
mother in uterus via placenta,
which also takes away waste
from baby
Oviparous – egg layers still have
various spawning behaviors
• Broadcast
• Just sprayed out there
• Substrate
• Put on something specifically
• Nest
• A nest is made and the other is
• Brooders
• Eggs held in pouch or mouth
invited in
Ovovivparity – eggs held in, not
laid until they actually hatch IN the
mom first
• Guppies
• Mosquito fish
• Many sharks
ovoviviparous sand tiger shark
• Mom has two uteri
• 100s of eggs are held inside,
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about 50 per uterus
Baby has a yolk like any other.
After hatching, they just stay in the mom for a
while, they are very small. (NO PLACENTA)
…. Only one, about 1ft shark comes out of each
uterus a few months later…fat and happy!!!!...
Why?
Sand tiger shark
• Marine bio trip picture.
Viviporous – momma provides
nourishment and takes away waste
via a placenta… not just a yolk
• This is common in mammals, (us, whales,
etc.) but extremely rare in fish
• Great white sharks have a mammalianlike placenta to nourish the babies till
strong
Reproduction summary
Oviparity, viviparity, ovoviparity
Egg: yolk or placenta, plopped out as egg or live
Oviparity
• Place where egg laid: broadcast, substrate, etc.
Ovoviparity:
• Held in till hatched, guppies
• even “uterus canabalism” in some sharks
Viviparity:
• Extremely rare in fish, only in sharks most likely
Fish Sex (gender)
Fish are NOT genetically determined to be
male or female.
They, like reptiles, are male or female based
on external forces
Gender in fish
1) “normal” - Some fish grow up to be male
or female and just stay that way
regardless – temperature of the egg
often determines male vs female
2) “Sequential hermaphrodite” – fish all start
out as one gender and then switch with
size or age
3) “Simultaneous hermaphrodite” – Fish
perform as male or female at the same
Gender in fish
1) “normal” - Most sharks and many fish
are “normal”
Gender in fish
“Sequential hermaphrodite” – fish all start
out as one gender and then switch with
size or age
Clown fish all start out male –
turn female only later if
big enough and paired
correctly.
Put two males together and
the older/bigger will be
come female
Gender in fish
“Sequential hermaphrodite” – fish all start
out as one gender and then switch with
size or age
Blue head wrasses
Most start as females,
and there are a few
“dominant” males that
run the harem.
Take out the dominant blue
head male – largest
female will turn into a
male and run the harem.
Gender in fish
“Simultaneous hermaphrodite” – Fish
perform as male or female at the same
time.
Hamlets – another reef fish is
both male and female at
the same time… he/she
can mate with any fish
that happens to come by
(They do not seem to
mate with themselves)
Thursday we dissect
Some things to keep in mind
1) Participation is required
2) Safe behavior is important.
3) Fish are preserved – smell is going to be
strong – just get over it.