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Topic 18: Feeding

� Why are there different feeding modes?

� What are the different ways of feeding in water?

� Suction feeding

� Non-suction feeding

� What are the different ways of feeding in air?

� Akinetic feeding

� Projectile feeding

� Kinetic feeding

� What are some specializations for prey capture?

Why are there different feeding modes?

� Most herps are ___________

� Eat wide variety of prey

� Also a wide variety of ways of

eating it

� Feeding modes depend on:

� _______________________

� _______________________

� _______________________

_______________________

C Harrison, vietnamtravelnotes.com, SM Deban, AmadeoPhotography, erodent.co.uk

� There is a huge difference between feeding in ______ versus _________

� Drag is much higher in water

� Ventilation of lungs and gills can create different problems

� Water: Primarily Suction feeding

� Air: Large diversity of feeding modes

Photos: © JEB, N Kley

Why are there different

feeding modes?

� Agkistrodon piscivorus eats fish in water and rodents in air

� How does the strike behavior differ in air and in water?

� What aspects are similar/same?

� Why do we see these differences in a (venomous) viper?

Photo © M Redmer; Vincent et al. 2005

Why are there different feeding modes?

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How do herps feed in water?

� __________ can be uni- or bi-directional

� Gilled animals are preadapted for

____________________________

� Water flows in through mouth, out through gill slits

� Feeding and gas exchange simultaneous

� Animals without gill slits must

use _______________________

� Water, air, food must flow in and out through mouth

� Need coordination of functions

� Cannot eat and breathe at the same time

Pough et al. 2004, Fig 11-1

Filter Feeding

� Common in tadpoles

� ______________ is raised and lowered using muscles

� Intake of water when buccal floor is ____________

� Water outtake when buccal floor is ____________

� Food is filtered from the water with elaborations of the gill slits and secreted mucus

Pough et al. 2004, Fig 11-6

Suction Feeding

� Extreme expansion of the buccal cavity

� Mouth opens

� Water and prey floods in

� Buccal expansion associated with the _________________

Pough et al. 2004, Fig 11-2, 11-13

Suction Feeding

� Occurs in some Testudines as well

� e.g. Pleurodira: Side-neck turtles, matamata

Photo © Pethelper.net; Pough et al. 2004, Fig 11-13

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Feeding in water

� Tadpole mouth part position

� Similar situation seen in many fishes

� Tadpoles feed on stream bottoms, in bromeliads, skim the water surface, and feed off rocks in ponds

� Based on mouth position

� Which one does what?

Pough et al. 2004, Fig 11-8

Terminal

Dorsal

Ventral

Subterminal

How do herps feed in air?

� What are key differences between the skulls of these animals?

� How do these differences influence feeding?

� Cranial kinesis� Akinetic

� Gymnophiona, Testudines, Amphisbaenia, Scolecophidia, Crocodylia

� Skulls highly fused, little motion other than between skull and mandible

� Kinetic� Squamata, especially snakes� Many moveable joints

www.digimorph.org

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Akinetic Feeding� ________________________

� Turtles have a very solid skull

� Not much space for muscles

� Emargination provides space for muscles by creating a _____________________

� Muscles fill the notch, but are positioned posteriorly

� Force of adductor mandibulae is directed

parallel to body axis

� Trochlear process redirects muscle fibers

� Evolved twice independently

Pough et al. 2004, Fig 11-15, 11-16

______________ Feeding

� Typically akinetic skull

� Tongue is long and mobile

� Independently evolved

� Urodela (most)

� Anura (some)

� Chamaeleonidae (all)

� Origin from a ________ __________________

� Subsequent elongation

Photos © SM Deban, Getty Images

Projectile Feeding

� In Urodela

� Short, sticky tongue diversified to various sticky ends

� Highly developed in ___________________

� Lack of lungs � buccal floor and hyoid free to evolve for

feeding

� Typical of salamanders in fast flowing streams, where buoyancy from lungs would negatively impact locomotion

Pough et al. 2004, Fig 11-19

Projectile Feeding

� In Chamaeleonidae

� Can project tongue 2x SVL!

� Associated with binocular vision for gauging distance

� Tongue moves fast, so the chameleon doesn’t have to

Photos © KP Bergmann, Getty Images

Projectile Feeding in Chamaeleons

� Also involves ______________ and a number of specialized muscles

� ___________________is wrapped around the processus entoglossus

� As accelerator muscle contracts, it squeezes off the PE and shoots out� Velocity: 5.8 ms-1

� Acceleration: 486 ms-2

� m. _______________ retracts the tongue after projection

Pough et al. 2004, Fig 11-24

Kinetic Feeding

� Seen in Squamata

� Extra joints in the skull

� Allow more mobility

� Allow more complexity

� “Lizards” have up to 3 joints in addition to the mandibular one

� ___________________

� Quadrate-Squamosal joint

� Loss of lower temporal bar allows more quadrate motion

� Leads to increased gape

� May increase bite force by lengthening mandibular in-lever

� ___________________

� Frontal-parietal joint

� Increased gape via elevation of snout

� Faster mouth closing, inc. bite force

� ___________________

� Parietal-supraoccipital joint

� Similar to mesokinetic

Pough et al. 2004, Fig 11-26

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Kinetic feeding

� Reduction in cranial kinesis

� ___________________

� Projectile feeding instead

� Lost meso & metakinetic

joints

� Dracaena (Teiidae)

� _________________

� Same reductions as in Chamaeleonidae

� Also specialized teeth for

crushing snail shells

� Various herbivores

www.digimorph.com; dinosaurcorporation.com

Kinetic feeding

� Static feeding

� Most lizards

� grasp prey and manipulate using tongue or environment

� ______________________

� Varanidae use the prey’s weight for ingestion

� Recall Newton’s first law:

� A body at rest will remain at rest

until a force acts on it

� Mouth moved relative to prey using jerking motions

Pough et al. 2004, Fig 11-28

Kinetic feeding

in snakes

� Large problem:� Small head relative to body

weight

� Need to take in a lot of food

� Solution: ________________� Allows eating of large prey

� Have extra skull and mandibular joints

� Increased connective tissue

� Decreased bone fusion

� Ability to move each side of the jaw independently

� Palatal teeth hold prey while jaws walk up it

???

Kinetic feeding in snakes

� A braincase has formed to protect brain from forces from prey� Down-growth of _____________ and ___________________

� Loss of meso & metakinetic joints

� New joints evolved� _______________ joint between frontals and nasals raises snout

� ________________ joint – drops toothrow

Pough et al. 2004, Fig 11-32

� Loss of mandibular symphesis

� Allows lateral spreading of lower jaw

Kinetic feeding in snakes

� Low cranial kinesis in some

� __________________

� Need rigid skull for burrowing

� Streptostylic

� ______________________

� Use teeth on lower jaw for “madibular raking” to overcome prey

� Eat small prey, but lots of them (e.g. termite pupae)

Pough et al. 2004, Fig 4-28

Prey capture

� Egg-eating snake (Dasypeltis)

� Use modified hypapophysis to crush shell & cut membranes

� Regurgitate shell

Anterior

DA Northcott-Corbis; Pough et al. 2004, Fig 11-37

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Prey capture

� Aglyphous snakes hold prey with teeth and ____________

� Morelia viridis and Corallus caninus have long teeth to ________________________

� Fish eaters just hold prey with teeth

� Most venomous snakes do not constrict

� __________________

� Often let go of prey after strike to avoid injury

Wikipedia

Envenomation

� High cranial kinesis has facilitated the evolution of __________________

� Opisthoglyphs have relatively short fangs

� Anterior shift in proteroglyphs and solenoglyphs provides space for longer fangs

Pough et al. 2004, Fig 11-42, www.digimorph.org

� Rotating maxilla in solenoglyphs

Envenomation

� Venomous snakes:

� Opisthoglyphs

� Solenoglyphs

� Proteroglyphs

� Muscles compressing the venom gland are not homologous

� Proteroglyphs: m. adductor superficialis

� Solenoglyphs: m. compressor glandulae

� Also different venom composition

� Proteroglyphs: primarily ____________

� Solenoglyphs: primarily ____________

� What does this tell us?

Pough et al. 2004, Fig 11-X

Origin of Envenomation

� Outside of Serpentes, only the ____________________ were considered venomous

� Some elements of derived venom are found elsewhere:

� Anguidae

� Varanidae

� Iguania

� New molecular phylogenies suggest that all of these groups form a clade

Pough et al. 2004, Fig 11-40

Envenomation

� 9 venom proteins are shared by the venom clade� Anguiforms have one unique protein, Helodermatidae have 2 more

� Serpentes have 16 derived proteins that have been sequenced

Fry et al. 2006

� Glands:

� Mucus

� Ancestral protein

� Anguimorph mandibular

� Derived, upper gland