Form versus Function in
Fishes
Megan Ennes
In conjunction with the North
Carolina Aquarium at Fort Fisher
Form versus Function
• Body shape fits the needs of the animal
• Outside (environmental) factors can
influence the development of an animal
Anatomical Directions
•
•
•
•
•
•
Dorsal
Ventral
Cranial
Caudal
Anterior
Posterior
Fish Parts
Mouth Shape
• A fish’s mouth tells
•
you where in the
water column it feeds
You can also tell how
it feeds
Superior Mouth
• Points up
• Feeds at the surface
• Often paired with a
flat back
Tarpon Megalops atlanticus
Terminal Mouth
• Located at the end of
•
•
•
the body
Usually feeds
midwater
“Normal” mouth
Eat things in front of
them
Yellow Tail Snapper
Ocyurus chrysurus
Inferior Mouth
• Located ventrally
• Usually bottom
•
•
feeders
Often accompanied
by barbels
Used for locating food
Atlantic Sturgeon
Acipenser oxyrhinchus
Elongated
• Greater surface area
to catch food with
Long Nose Gar
Lepisosteus osseus
http://rol.freenet.columbus.oh.us/aquatic_long.gif
Blue Ribbon Eel
Rhinomuraena quaesita
Tubular Mouth
•
•
•
•
Terminal mouth
Often fused
Suction feeding
Straw
Lined Seahorse
Hippocamus erectus
Body Shape
• By looking at the
overall shape of a
fish, you can get an
idea of where they
live within the aquatic
environment.
Body Shapes
• Fish that live at the surface usually have a
flattened back and an upturned mouth.
• Fish that live in slow-moving waters
usually have tall bodies and are laterally
compressed.
• Bottom-dwelling fish have flattened bellies
and inferior or down turned mouths
Surface swimmers
• Fish that live at the surface usually have a
flattened back and an upturned mouth.
• Flat Needlefish
Slow Moving Waters
• Fish that live in slow-
moving waters usually
have tall bodies and
are laterally
compressed.
Lookdowns
•
• Selene vomer
Bottom Feeders
• Bottom-dwelling fish often have flattened
bellies and inferior or down turned mouths
Southern Stingray Dasyatis americana
Fast Moving Water
• In fast moving waters
•
a slender, torpedo
shape is better
This body shape is
also good for fish who
live far from the reef:
speed
Atlantic Mackerel
Scomber scombrus
Fat and Wide Bodies
• Good maneuverability
• Better for close to the
•
reef
Easier to move
around corals
French Angelfish
Pomacanthus paru
Eel-like body
• This long body shape
•
is perfect for moving
through small spaces:
especially holes and
caves
The trunk is
undulated to provide
the propulsive force
Green Moray Eel
Gymnothorax prasinus
Caudal Fin: Tail
• The caudal fin, or tail, is used for
propulsion, or movement, in most fish
species.
Lunate Tails
• Fishes with lunate are
•
strong, fast
swimmers.
They are capable of
swimming for long
periods of time
Yellowfin Tuna Thunnus albacares
Forked Tails
• Fish that spend a lot
of time swimming
often have forked
tails
Channel Catfish
Ictalurus punctatus
Truncate and Rounded Tails
• Fishes with truncate
•
or rounded caudal
fins are usually
strong, slow
swimmers.
Fishes that live near
the reef often have
this type of tail
because it aids in
maneuverability.
Truncate
Rounded
Majestic Angelfish
Pomacanthus navarchus
Heterocercal Tail
• A tail with a long
•
upper lobe and a
shorter lower lobe
Common in Sharks
Juvenile Tiger Shark
Galeocerdo cuvier
http://www.flmnh.ufl.edu/fish/gallery/descript/TigerShark/juvenile.JPG
Eel-like Tail
• The propulsive force
•
for a fish with this
type of tail begins in
the trunk of the body
and moves as a wave
down through the tail.
This shape is great
for fitting into holes
and tunnels.
Ocellated Moray Eel
Gymnothorax saxicola
Create your own fish
• Use the second worksheet we gave you
• Cut out the different fish shapes
• Choose one of each and glue them to a
sheet of paper
• Color your fish and give it a design
• Name your fish
• Write a paragraph telling the function of
each part, where it lives, ect.
Examples of coloration
What’s next?
• Choose a tank
• Choose 3 fishes to sketch in your
notebook
• Find the name of your fishes
• Label that parts of your fish using the
worksheet we just made
For each fish answer the following
questions:
1. Where do you think this fish lives on the reef? What
about this fish leads you to that decision?
2. Where do you think the fish eats? What mouth shape
does it have?
3. Is it a schooling fish or does it appear to be solitary?
4. Is your fish territorial? How can you tell?
5. How does your fish swim? Is it built for speed?
Maneuverability? How can you tell?
6. Does your fish live close to the reef or far away? What
body shape does it have?
7. Is your fish well adapted to its environment? Why or
why not?
After your observations:
• We’ll come back to the room and talk
about what fish we chose.
• We’ll discuss as a group what we decided
for each fish.
• We do not expect you to be right, just be
able to explain why you made the decision
you did.