Download Chapter 8 Mola mola or Sunfish Mola Mola Fish cardiovascular

Chapter 8
Marine Fishes
Mola mola or Sunfish
• Heaviest bony fish in the world, up to 2300
kg
• Enlarged anal and dorsal fins
• Much of the skeleton is cartilagenous
• Spinal column is very short (1 inch)
• Eats jellyfish
• http://www.youtube.com/watch?v=73iY8cE
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Mola Mola
• Related to pufferfishes and trigger fishes
Fish cardiovascular
physiology
Fish Gills
• The construction of the gill is the same in all fish – gill
arch supports the entire structure, gill rakers are on the
forward surface of the gill arch and gill filaments trail
behind the gill arch
• Like in the human lung, exchange of oxygen and carbon
dioxide takes place on these surfaces
• Gill rakers can also function in filter feeding
The Circulatory System
• Fish have a two chambered heart that
serves to pump blood throughout the body
(in contrast to the 4 chambered heart seen
in mammals)
• A system of arteries, veins and capillaries
takes blood to the body tissues and
returns it for rere-oxygenation by the gill
filaments
Swimming Patterns
Fish locomotion
• Fish exhibit an “s-shaped”
shaped” swimming
pattern
• Bands of muscle along the body called
myomeres drive this swimming motion
• Depending on the type of fish, different
fins may be used primarily for the forward
movement
Swim tunnel
http://www.youtube.com/watch?v=
P-c-EXmTmQY
• http://www.youtube.com/wa
tch?v=Uw13qOnDVLE
Eel anguilliform locomotion
Studying swimming hydrodynamics
Some biomechanics of swimming
Thunniform swimming
• Burst swimming is in the range of 5-10 body
lengths per second
• Drag increases as the square of velocity.
• Therefore a 2 m tuna swimming at 20 m/s
experiences 4 times more drag than a 1 m tuna
swimming at 10 m/s
• Drag on a rigid body is less than on a flexible
body
– “kick and glide” is a way to take advantage of this
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Billfishes, tunas, some sharks
Stiff caudal fins, high aspect ratio (crescent shaped)
90% of thrust comes from the caudal fin.
Stiff vertebral column
Head does not move side to side. Caudal fin acts like a
“propeller”
• Tendons attach body musculature to caudal peduncle in
some cases runs over the peduncle like a line over a
pulley
• Fins can be depressed into grooves and recesses.
• Bulge of eye is streamlined with “adipose eyelids”
Caudal peduncle
Bluefin thunniform swimming
• http://www.youtube.com/watch?v=s272wD
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Biochemical adaptation to fast
swimming
• Tunas have some of the highest levels of
enzymes for glycolysis and aerobic respiration
• Lactic acid is the endproduct of glycolysis and
sprinting, causes a drop in pH if sprinting is
prolonged
• In tunas the muscle pH is buffered by amino
acids, particularly histidine
• Marine animals in general are rich in free amino
acids including glutamate, glycine, and taurine.
MIT robotuna
• overall goal of developing a better
propulsion system for autonomous
underwater vehicles, or AUVs
Generating lift
Swimming Patterns
• In sharks, a swim bladder is absent (although
there is a large lipidlipid-rich liver to help in
buoyancy) – therefore, sharks tend to sink when
not in motion and there is no lift from the swim
bladder while swimming either
• Also their blood is full of urea
• While swimming, sharks are aided by the “lift”
lift”
provided by the position and stiffness of the
pectoral fins
Swimming Patterns
• In bony fish, pectoral fins are not needed for lift
and thus are normally not stiff in construction
(exception: fast swimming species like tuna,
billfish, etc)
• In contrast, the pectoral fins in many bony fins
are flexible and used for maneuverability
• In some slowerslower-swimming species, forward
movement is mainly provided primarily by the
pectoral fins
Billfishes
http://www.youtube.com/watch?v=B2kQF7eWkIs
Another cool type of fish:
Billfishes
Swordfishes also have heated
brains and eyes
Behaviors in Fish
• Schooling
– Schooling is used by a wide variety of fish
– Schooling makes it possible for a group of
smaller fish to appear much larger (as thus
avoid detection by predators), not the case in
the video
– May be hydrodynamically more efficient
– It also makes it harder for a predator to
capture any one fish
– Because of this, many fish school as juveniles
– About 4000 species school as adults
•
Specialized heating system warms brain and eye up to 10-15
degrees C above water temperature
Some deep sea fishes
• Also called midwater or mesopelagic
• Many filter plankton using their gill rakers
• Others are predators with extreme
adaptations for prey capture
Myctophids (lantern fishes)
• One of the most numerous of all fishes
Hatchet fish
• Large tubular eyes pointed upwards
Cyclothone (bristlemouths)
• This genus may
contain more
individuals and
biomass than any
other fish genus
Snipe eel
• Tiny hooked teeth entangle prey
• 5 ft specimen weighs a few ounces
Chiasmodon (black swallower)
viperfish
Dragonfish
Most Important Characteristics
of Marine Fish
• Red light organ under eye