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VERTEBRATE ZOOLOGY
(VZ Lecture16 – Fall 2012 Althoff - reference PJH Chapter 12)
Turtles
Beyond Amphibians….or not???
• Turtles essentially lack diversity in life history
strategies compared to salamanders…
a) ____ lay eggs (vs. some eggs, some live
livebirth, etc.)
b) ____ exhibit parental care of hatchling
(vs. some that stay with
eggs, young)
c) generally low reproductive productivity
(later maturity, few young
per effort for turtle)
Not much change…terrestrial & aquatic forms
• Thought to have emerged in the Triassic (~_____
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MYA)
Little change suspected in design/function from
early versions
Shell morphology reflects the ecology of this group:
Large terrestrial tortoises: high domed
shells & elephant-like feet
Small tortoises: front legs flattened for
burrowing
Pancake tortoise: flat shell, agile
Box turtles: moderately domed, flexible
plastron
Etc. See Fig. 12-1, pg305 PJH
Classification
• Class: Anapsida
• Order: Testudomorpha (~ 300 species)
• Suborders
______________ (10 families)
______________ (3 familes)
Suborder: Cryptodira
• Cryptodires
• Greek crypto =
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dire =
Retract head into the shell by bending the
neck in a _________ S shape
10 families
all turtle species find in ____________ are from
this suborder
None found in Australia
Marine turtles fall into this suborder
Pelvic girdle _____ fused to carapace
External adductor tendon “over” trochlear
process that is part of otic capsule
Suborder: Pleurodira
• Pleurodires
• Greek pleuro =
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dire = neck
Retract head into the shell by bending the
neck ________________
3 families
Species found in South America, Africa,
Madagascar, Australia
All extant species are at least semi-aquatic
Pelvic girdle ____ fused to carapace
External adductor tendon “over” trochlear
process that is separate from of otic capsule
Phylogenetic Relationships of Turtles
• Two “twists” here for this group
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a) many ancestral features
b) many highly specialized characters ____
shared with any other group of
vertebrates
Turtles have anapsid skulls….but
a) ______ unique
b) _____________ skeletons are unique
Result two competing hypotheses:
A) origin from ______________
B) origin with ___________ reptiles
Amniotes
Sauropods
Diapsids
Lepidosaurs
Squamates
Archosaurs
B
A
DIAPSID REPTILES
PARAREPTILES
Fig. 12-3, p307 PJH
• Position of the
ancestral
parareptiles
trochlear
process
cryptodirans
pleurodirans
trochlear
process
EXTERNAL
ADDUCTOR
TENDON—
__________
vs.
__________
suborder
differences—
TROCHLER
PROCESS
Fig. 12-4, p308 PJH
Structure & Function - Highlights
• Covered in bone
• Limbs inside ribs
• Horny beaks instead of teeth
• Lungs attached to carapace dorsally and
ventrally
loggerhead sea turtle
Snapping turtle
Carapace – “foundation”
A
• Composed of _____________ that grows from
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59 separate centers of ossification
8 ________ along the dorsal midline
a) forms “neural” series
b) fused to neural arches of vertebrae
8 paired costal bones, lateral to neural bones,
fused to broadened ribs
Ribs are EXTERNAL to the girdles (unique
among vertebrates)
11 pairs of peripheral bones plus 2 unpaired
bones (uchal & pygal) form margin of carapace
CARAPACE
“foundation”
A
Fig. 12-5, p309 PJH
Carapace – “covering”
B
• Composed of ______________ that originate
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from _____________ layer.
These scutes do NOT coincide with the position
of the underlying bones
5 rows of central scutes
4 rows of lateral scutes border central scutes
12 marginal scutes (marginals) on each side
turn under the edge of the carapace
B
CARAPACE
“covering”
horny
covering
Fig. 12-5, p309 PJH
Carapace – “inside view”
C
• 10 trunk vertebrae (8 in neck)
• Pleurodires: pelvic girdle fused to dermal
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carapace (i.e., bony portion)
vs.
Cryptodires: 2 sacral vertebrae have broadened
ribs that meet ilia of the pelvis (hence, not
“fused” to carapace)
CARAPACE
“inside view”
horny
covering
C
Fig. 12-5, p309 PJH
Respiration
• Primitive amniotes used movements of the rib
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cage to draw air into the lungs and force it out.
Because ribs are fused in turtles to their rigid
shells, they cannot use that method to breath
Lungs attached to carapace dorsally and
laterally. On the ventral side, they are attached
to a sheet of ______________ connective tissue
that is itself attached to the viscera. Weight of
this tissue keep this area stretched downward
So, turtles produce pressure changes by
contracting muscles that force the viscera
upward (compress), then other muscles that
increase volume of the visceral cavity
Transverse
abdominus
USED IN EXHALATION
Fig. 12-7, p312 PJH
SERRATUS
ABDOMINAL
OBLIQUE
USED IN INHALATION
PECTORALIS
Fig. 12-7, p312 PJH
Respiration…con’t
• Bottomline, turtles have done without ribs to help
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with ventilation
Some variations noted among turtle species:
a) aquatic turtles can use hydrostatic
pressure of water to help move air in
and out of lungs
b) many aquatic turtle species capable of
absorbing 02 and releasing CO2 to
the water, mainly via the ___________
and
____________
Soft-shelled turtles have been observed to use
hyoid apparatus to move water in and out of the
pharynx…resulting in most 02 coming in that way
Australian turtle almost exclusively uses “______”
respirationpumps H20 in and out
Respiration & Circulation
• Turtles: 3-chambered heart
• Turtles exhibit “right-to-left intracardiac shunt”
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process at times:
a) result is some deoxygenated blood
bypasses the lungs and flows into
systemic system
b) “shift” occurs in heart (i.e., “intra”) rather
than between major blood vessels
Right-to-left intracardiac shunting is not unique to
turtles…snakes, lizards, and crocodilians known
to do this, too.
May help match lung ventilation with pulmonary
gas flow, may be helpful for those species that
dive (i.e., aquatic species)…results in more
effective use of O2 in lungs.
Basking: Temperature & Etc. Benefits
• Some species exhibit basking behavior.
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The
result/need raise body temperature. Raising
body temperature can result in:
a)
b)
c)
….otherwise these processes
go very slowly or halt altogether
Other benefits:
a) rid themselves of algae & leeches
b) activate Vit D, impacting Ca deposition
Social Behavior & Courtship
• Social interactions usually facilitated by tactile,
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visual, and olfactory signals
Many pond turtle species have distinctive stripes
of color on their head, neck, forelimbs, hindlimbs,
and tail.
Among terrestrial turtles, tortoises known for
vocalizations (grunts, moans, and bellows)
during courtship. Some produce pheromones
during breeding period—species and sex specific
Herds of tortoises have social hierarchies,
determined by aggressive behaviors, impact
access to food, mates, and nesting sites
Nesting Behavior
• All turtle species are _____________
• Females use hind limbs to excavate a nest in
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sand or soil.
_______ species typically: 4-5 eggs
_______ species typically: 100+ eggs
Some species lay soft eggs, some hard eggs
Typically embryonic development takes 40-60
days, with soft-shelled eggs usually developing
______ rapidly than hard-shelled eggs.
Some lay eggs in spring, others in late summer
and fall (diapause) that hatch next spring….
What would be an advantage of such a strategy?
Environmental Effects on Egg Development
• Temperature, wetness, O2 and CO2 concentrations
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impact embryonic development
For many species, sex of hatchlings is determined
by temperature (also known to occur for
crocodilians, tuatara, and some lizard species)
Temperature usually influences size of individuals,
as it relates to sex. For most species, females
larger than males. Thus, under higher tempregimes, more females are result (just opposite in
other taxa). Usually a 3-4OC difference results in
these patterns
Implications are critical to conservation of
endangered species
European pond turtle species
NA Map Turtle
NA Map Turtle
Lizard Agama agama
Fig. 12-10, p317 PJH