Exam II
Thurs Nov. 18th (Energetics /Performance
through through Foraging)
Feeding
Most amphibians and reptiles are carnivores
Feeding in Crocodilians
Arthropods are the main
prey source
Many species lie somewhere
along the continuum between
strict herbivory and strict
carnivory
Rigid skull and hinged lower jaw (akinetic)
Open their mouths by lifting their heads not lowering
their jaws.
Virtually no opening force but a powerful crushing
force
Feeding in Crocodilians
Often use rotational feeding on large prey,
AKA the “death roll”
Secondary palate allows crocs to breathe
through their nostrils while floating
Use hyoid apparatus to push food through
the oral seal
Ingest stones, potentially to help grind
hard food items and/or for ballast
Dispatch food by drowning it, therefore
must be able to outlast prey
underwater…highly acidic blood
(as low as 6.1), the lowest blood pH in
the animal kingdom
http://www.youtube.com/watch?v=wZdWRR5tRmc
hence ability to feed on turtles
Step right up and see the strongest
jaws in the animal kingdom:
Salty – 5,000 lbs/in2
Hyena – 1,000 lbs/in2
Great White – 400
lbs/in2
Rottweiler – 335
lbs/in2
Bill “Superfoot” Wallace
can deliver a kick with
1,500 lbs/in2 of force
behind it
Human – 200 lbs/in2
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Tuatara are carnivores
Vertebrate and invertebrate prey
Two rows of teeth on the upper jaw and
one on the lower jaw. Teeth on upper
jaw overlap bottom teeth, unique among
extent animals
Small insect prey are captured with the
tuatara’s sticky tongue
Larger prey are
impaled on front
teeth and mashed
and sliced by the
rear teeth
Projectile feeding in salamanders
Seizing prey by tongue projection…
Tongue projection has evolved independently in many reptile
and amphibian lineages
frogs, several salamander groups, and chameleons
Requires stereo vision
Tongue can shoot out 40 – 80% the length of the animal’s body
in just 10 milliseconds (~50 times faster than the blink of an
eye) – needless to say, too fast to see.
Ballistic tongue projection
“Like shooting a watermelon seed from between your
fingers”
Pedastal-like tongue tip on floor of mouth (attached to
hyoid apparatus)
Paired hyoid arms lie flat on floor of mouth
Hyoid muscles contract and “fire” hyoid rod forward with
tongue tip at the end
Power output peaks at values greater than for any
vertebrate muscle recorded by more than 10 times
Ballistic tongue projection
See http://autodax.net/feedingmovieindex.html
Stephen Deban
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And the award for most powerful muscle in
the Animal Kingdom goes too…
Chameleons have similar
projectile feeding mechanisms
The giant palm salamander
(Bolitoglossa dofleini )
18,000 watts/kg of muscle
Former champion the
Colorado River toad (Bufo alvarius)
9,600 watts/kg of muscle
Can project tongues twice their body length
Tongue tip is a sticky pad with a powerful accelerator muscle
At rest this muscle is wrapped around a long extension of the
hyobranchial skeleton
Tongue is projected using the hyoid apparatus
Can capture insects, small lizards, and even the occasional bird
or mammal
http://www.youtube.com/watch?v=lNzsGiVvOgA
http://www.youtube.com/watch?v=hlrzM_fl534&featu
re=related
http://autodax.net/animalmoviesdeba.html
Chameleo calyptratus
Mobile and independent eyes
Vision in Chameleons is not stereo-based but is based on
independently operating eyes
Measure distance by focusing,
not by binocular vision
Chameleo
deremensis
Processus entoglossus
Projectile feeding in Anurans
Use a "flick tongue" mechanism
The tongue is attached to the front part of
the mouth where two sides of jaw join
Frog yanks attachment point downward and
"flips" posterior part of tongue forwards
Tongue weight stretches it to twice its length
and slaps down on prey, which is secured
with mucous and withdrawn back into mouth
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Feeding mechanisms in anurans
In basal clades the tongue is flipped out by contraction of
the genioglossus muscle and is aided by a fulcrum-like
action from the submentalis (mechanical pulling)
In derived clades the submentalis propells the
genioglossus muscle forward (inertial elongation)
The hyoglossus muscle retracts the tongue.
Swallowing in
adult anurans
Many anurans (and
salamanders) depress their
eyes while swallowing
Eyeballs are firm and
surfaces extend into the
mouth and onto the palate
Lowering them may help
crush prey and force prey
down throat
Rana pipiens
Feeding in Ceratophrys and Pyxicephalus
Highly carnivorous South
American horned frogs and
African bullfrogs
Large heads, heavily ossified
skulls, sharp teeth
Capture prey directly with
the jaws
Feeding in water: Suction feeding
Aquatic salamanders and larvae, aquatic
frogs and tadpoles, some turtles
Feeding in water has advantages
Like bobbing for apples….or poodles
Food buoyant and swallowing needs no
saliva
But pressure waves can push food away
…
"gape and suck" mechanisms
Require:
Accurate alignment of head to prey
Good timing
Rapid expansion of the buccal cavity to build up
negative pressure and suction forces.
Via the hyoid apparatus (musculature) = the floor of the
mouth
When hyoid suddenly depressed, creates the volume
increase that draws water suddenly into mouth cavity.
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Suction Feeding in Tadpoles
Diets of tadpoles consist of algae and bacteria = microphagy.
Requires both a suction mechanism to draw particles in and a
filtering apparatus to capture them.
Tadpoles use mouth, buccopharyngeal cavity, and gills
simultaneously for respiration and feeding.
Suction feeding in Salamanders
Cryptobranchus are able to capture
their prey alongside and not just
directly in front of head.
Depends on asymmetrical movement
of lower jaw
Permitted by a ligamentous
attachment of the left and right
dentaries at front of jaw.
Hymenochirus boettgeri
http://autodax.net/
http://www.youtube.com/watch?v=aF6PGPJhgYU
Some species use prey attraction, tongue
wiggling, with suction feeding, e.g., the
alligator snapper (Macroclemys temminckii).
Suction Feeding in Turtles
Head shoots forward, nostrils close, mouth
gapes, esophagus opens to maintain inward flow
of water as mouth closes
Excess water filtered out through keratinized
beak sheath (rhamphotheca) that rings mouth
and serves as “teeth.”
This is a continuously growing structure.
Mata mata feeding movie:
http://www.youtube.com/watch?v=LB3IlHxSwho
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Tadpole Feeding Structures
Herbivory
Not widespread in
amphibians with one
prominent exception
Anuran tadpoles
Eat the bacterial and algal scum that
covers all objects in water.
Typically specialize on selected
portion of water column and style of
harvesting.
Sirens are the only salamanders
known to regularly eat plants (mainly
Elodea).
Microparticles are scraped or rasped from surfaces
Use several rows of keratinized teeth (labial teeth)
on a oral disk about the mouth.
Extremely useful in identification of tadpoles
Siren lacertina
Herbivory - Reptiles
Among lizards
Among turtles:
Iguanines
a few agamids
a few skinks
tortoises (testudinids)
some emydids
Mainly consume plant foliage and occasionally
take some animal matter.
Gray treefrog tadpole
Sea turtle herbivory
A good example is the
green turtle (Chelonia
mydas)
Eats either algae or
seagrass but not both
owing to need for
different gut floras to
digest these foods.
Create carefully grazed
and maintained seagrass
pastures of new growth
that are harvested daily.
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Symbionts and herbivory...
No vertebrate produces the cellulase needed to
breakdown cellulose in the cell-wall fiber of
vascular plants
Depend on gut microflora of cellulolytic bacteria
Ferment plant material and liberate nutrients that
the animal absorbs.
Gut often includes an enlarged colon with many
chambers -- a big fermentation vat.
Requisites for herbivory…
To function well, needs:
a constant food supply,
slow passage time to permit digestion,
appropriate gut pH,
removal of fermentation waste by-products.
challenge for temperate-zone species that undergo
aestivation
must restore microflora each spring or retain a
microflora bolus.
Restoring microflora…
Restoring microflora…
Gopher tortoises (Gopherus polyphemus) apparently
intentionally deposit droppings in den entrance in fall
and reconsume them in spring.
Carnivory is
more
common
than
herbivory
Green Iguana (Iguana iguana) hatchlings leave
soils and seek out in just a few days adults in
tops of trees -- find droppings and inoculate
themselves with the correct microflora.
VENOMOUS REPTILES
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Venomous reptiles
Found in < 20% of snake species
Evolved independently in several distinct lineages
of snakes
Viperidae
Elapidae
some colubrids (1% of venomous snakes)
Venomous lizards
Difference between venomous and poisonous
Venom compounds used to immobilize large
prey
Cardiotoxins – affect the heart and may cause heart
failure (elapids and vipers)
Neurotoxins – lead to respiratory collapse- quick
immobilization
Hemotoxins - destroy capillary walls, causing
hemorrhages (vipers, pitvipers, cobra, boomslang)
Others foster clot formation throughout the
circulatory system (vipers) or destroy blood cells
Venom Delivery- front-fanged
Depends on highly evolved saliva
glands and modified teeth
Very much like a hypodermic needle
a gland to produce the venom,
a duct to transport venom to injection
system,
fangs (modified teeth with hollow canals
or grooves).
Venom continually produced and
stored in a venom-gland chamber.
When prey bitten, muscles around
venom chamber contract and send
venom down duct to fang canal.
Venomous snakes in the U.S.
Every state in the U.S. except Maine, Alaska and
Hawaii is home to at least one venomous species
20 venomous snake species in the U.S.
Most are pit vipers (subfamily Crotalinae), which
include rattlesnakes, copperheads and
cottonmouths
Correlation of venom type and
prey type
Two species of coral snakes
(family Elapidae)
Venom Delivery – Front fanged
Front-fanged: vipers
(solenoglyph) and elapids
(proteroglyph)
In elapids the fangs are
shorter and remain vertical
when the mouth is closed
In vipers the fangs are long
and lie against the roof
of the mouth when closed
Thin neck, thick body, fecal
matter as ballast!
Elapid venom (front-fanged)
Polypeptides interfere with
neuromuscular transmission to
rapidly immobilize prey
Most eat elongate prey – snakes,
lizards, eels
Include:
mambas (Dendroaspis) of Africa;
cobras (Naja and other genera) of Asia
and Africa;
kraits (Bungarus) of Asia;
coral snakes (Micrurus) of the
Americas;
Australian elapids
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Venom Delivery – Rear fanged
Viperid venom (front-fanged)
Venom contains toxins and enzymes
Enzymes begin digestive process
Generally take large prey
(up to 150% of their own mass)
Have an extremely wide gape
Vipers include:
rattlesnakes (Crotalus) moccasins (Agkistrodon), and lance-headed
vipers (Bothrops) of the Americas;
Russell's viper (Daboia russellii) of Asia;
puff adder (Bitis arietans) and Gaboon viper (Bitis gabonica) of Africa.
Colubrids are rear-fanged
NY: Hognose snake (Heterodon platirhinos)
Venomous colubrids deliver small amounts of
venom slowly
Less effective than
venom delivery in
vipers and elapids
Duvernoy’s gland
Macrophistodon flaviceps
Orange-necked keelback snake
THE HARRIS POLL #49, August 18,
1999 WHAT WE ARE AFRAID OF
Snakes top the list of the
most common fears, with
more than a third (36%) of
all adults saying they are very
afraid of them.
Harris Poll of 1,015 adults
surveyed between July 15
and 20, 1999.
A rational fear?
White males had the highest (76%) incidence of
death by reptile envenomation (comprising only
41% of the US population)
Males 25 to 34 years old had the most deaths
(19.6%, but 7.1% of US population)
Large proportion of snake bite victims
are intoxicated
Young, white male Southerners
appear to be at greatest risk
A rational fear?
Most snakebites in the U. S. are
caused by individuals who are
trying to catch, kill, or handle the
snake, often a captive specimen.
How many people in the U.S. die from snakebite
each year?
10 deaths
How many are bitten by venomous snakes?
Venom is expensive – snakes do not always inject
venom when they bite (dry bites)
~1500
A rational fear?
Worldwide as many as 30,000 – 40,000
deaths from snake bites per year
Concentrated in tropical regions
King Cobra – Longest venomous snake
Black Mamba – World’s deadliest snake?
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Antivenom (antivenin?)
Step 1: milk the snake
Step 2: inject venom into
a large domestic animal
Step 3: tap lymphatic
system and harvest
antibodies
Step 4: freeze and inject
when needed
Antibodies bind and
detoxify venom
Venomous lizards
Gila monster
Heloderma suspectum
Southwest U.S.
Venom causes blood
pressure to drop and
affects breathing
Beaded lizard H. horridum
Mexico - Guatemala
Securing Prey: Constriction
Just another way to subdue prey before eating…
Feeding specializations in SNAKES
Securing Prey: Constriction
Snakes use constriction to kill mammals from mice to antelopes.
Involves wrapping loops of the body around a prey animal to restrain it
so that it cannot escape or injure the snake
Appears to involve continuous squeezing, but often is actually
intermittent
Assumed to kill prey by suffocation, however, constriction
often kills small mammals faster than would be expected if
suffocation were the immediate cause of death
In many snakes, constriction may be strong enough to
collapse the blood vessels in small prey, and stop the heart
from working
Tentacled snake can predict the future
location of its prey!
Aquatic, sit-and-wait predator from southeast
Asia
(What are the tentacles for??)
Exploits a common escape response (C-start) of
its fish prey (Catania 2009)
http://www.youtube.com/watch?v=urBp2X5mBmQ
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Sensory organs in pit vipers
Cranial Kinesis - Highly flexible skull
Common in snakes and many lizards
Cranial Kinesis in Snakes
How is swallowing achieved?
Snake advances all tooth-bearing bones on one side
of the head out, over, and then against the prey item
to engage the teeth
Then other side advances
Cycle repeated
“Walks" its head over
and around the prey item
Sensitive infrared receptors
Allows the snake to ‘see’ with a
combination of heat and light
Can easily locate ectothermic prey
in the dark
Any other
uses?
Usually a joint in the middle of each
mandible, enabling the jaw to expand
outward.
Mandibles themselves can be
disarticulated from skull (snake resets
jaws by yawning-like movements).
Each mandible covered with sharp,
curved teeth
How is swallowing achieved?
Extra bone growth protects snake's brain from
struggling prey
Snakes have no pectoral girdles or sternum so ribs
are not fused and large prey items can pass
unobstructed.
Once in throat, peristaltic contractions of esophagus
move prey backward to snake's stomach.
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Opening to the trachea is at the front end
rather than in the back of the throat
Egg eating snakes
Climb into a nest, locate an egg as big as snake’s
head, and pushes head over egg.
The backbone is arched over the egg
At the back of the throat are sharp projections of
the snake's vertebrae
The egg is cracked when muscles are tensed and
the egg contents are moved back to stomach
Undulations reverse, snake gapes, and egg-shell
packet ejected from mouth.
http://www.youtube.com/watch?v=LLk4rsCNFFU
Snakes can eat large prey,
but how large is too large?
Snakes can eat large prey,
but how large is too large?
Python Bursts After Trying to Eat Gator!
(Associated Press Oct 5th 2006)
A 13-foot Burmese python burst after it apparently
tried to swallow a live, 6-foot alligator
Burmese pythons have been abandoned in the
Everglades by pet owners
Seems to be a thriving population in the Everglades…
Coda…
“The Adventures of Owen and Mzee”
Here’s Owen the hippo and Mzee the tortoise. Owen was orphaned after the
great 2004 Tsunami hit Kenya. The rangers who saved him sent Owen to live
at the zoo where he bonded with Mzee, a 130-year-old male tortoise.
End: Feeding
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Owen followed Mzee as if the tortoise was his mother. At first Mzee was
annoyed, but he eventually accepted Owen. Now they are inseparable.
They eat together.
And play together.
And even nap together.
They protect each other if anyone gets too close.
Until Owen got hungry.
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Just kidding!
They are still friends today.
Keep up on Owen and Mzee – watch a documentary about the friends at http://www.owenandmzee.com/omweb/
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