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VERTEBRATE ZOOLOGY
(VZ Lecture19 – Spring 2012 Althoff - reference PJH Chapters 13 & 14)
Lizards & Snakes & Tuatara
Part III
Photo: Steve Huskey
Data from W. Hayes, Loma Linda U.
Venom
• Two known species of ________ produce venom:
Gila monster (Heloderma suspectum )
beaded lizard (Heloderma horridum)
(venom is slowly delivered via grooved
teeth on bottom jaw)
• Two effects:
•
•
a) kills prey
b) speeds digestion after
swallowing prey
A complex mixture of enzymes & other
substances…with _________ amounts of toxicity
7 major groups of venomous compounds:
most are a “cocktail” of compounds
Venom components & effects
Proteinases
Hyaluronidase
L-amino acid oxidase
Cholinesterase
Phospholipases
Phosphatases
Basic polypeptides
Tissue destruction
Increases tissue permeability
Attacks wide-variety of
substrates, tissue
destruction
Unknown
Destroys cell membranes
Breaksdown ATP, etc.
Blocks neuromuscular
transmission
Point:
Data from W. Hayes, Loma Linda U.
s. Pacific rattlesnake
cottonmouth
Point:
Data from W. Hayes, Loma Linda U.
Foraging Behaviors: Squamates
• Three basic foraging modes observed among
lizards (summarized from Table 13.5, p384 PJH):
1) sit-and-wait
2) curising forager
3) widely foraging
• Endurance
• Sprint speed
• Daily energy
expenditure
• Size of home
range
• Reproduction
(relative mass
of clutch)
• Risk of
predation
?
?
?
intermediate
?
?
Risks and Predator-Escape Mechanisms
• Risk of predation is greatly elevated for the
•
•
•
•
cruising and widely foraging lizard species
compared to sit-and-wait hunters
Typically, they have slimer body design, slimer
tails, and more elongate tails. Also, many have
stripping patterns that produce optical illusions as
they move.
Like some salamanders…lizards, some snakes,
and the tuatara can exhibit ____________
_____________
…defined as “self-amputation” of the tail
It may be followed by regeneration of a new tail
Caudal Autotomy of Squamates
• Occurs at caudal (tail) vertebrate….usually all
•
•
•
caudal vertebrate can “fracture” except 4-9 most
anterior.
Actually have distinctive “fracture plane”
a) caudal muscles are segmental
b) w/ pointed processes (of vertebrae) that
are interdigitate
c) caudal arteries have sphincter muscles
just anterior to each fracture site & veins
have valves
Autotomized tail continues to twitch for several
minutes
Replaced tail portion lack “fracture” plane portions
Social Behavior
• Communication achieved using visual, auditory,
chemical, and tactile signals…resulting in
maintaning territories and choosing mates.
• Many species exhibit dominance hierarchies
• Territorial lizards using a) push-up, b) head
bobs, and/or c) displays of the gular fan.
• Combinations of these actions represents what
is called a _____________________ (DAP)
• DAPs can be species specific…as the case
with the Iguanian lizards in the genus Anolis
(8 species of which are found in Costa Rica illustrated
in PJH Fig. 13-11, pg353)
SIMPLE COMPOUND
COMPLEX
GULAR FANS
Simple 
Compound 
Complex 


Green anole
(Anolis carolinensis)
Gular fan…extended
sometimes known
as the
____________
Brown anole
(Anolis sagrei)
A
B
C
Fig. 13-12, p354 PJH
Green Anole behavioral displays
A• ________________________MALE response to
intruder to territory
a) head bob
b) dewlap extended
c) nuchal & dorsal crests d) eyespot expanded
B• __________________intruder in close proximity
and is a MALE
a) head bob
b) dewlap extended
c) nuchal & dorsal crests d) eyespot f) facing
C• _____________ MALE “posturing” for female
a) head bob
b) head high
c) dewlap extended
d) no nuchal or dorsal crests
e) no eyespot
Reproduction
• Wide range of modes: __________trophy 
_________trophy
• Viviparous species have chorioallantoic
placentae; in the Brazilian skink 99% of mass of
fetal size is achieved by transport of nutrients
across the placenta
• Some give live birth but usually few
young…eliminates possibility of multiple clutches
during a given year.
• Generally, beyond some presence at nests
during incubation there is no extended parental
care of young (much like salamanders)
Parthenogenesis
• Defined: reproduction by females ____________
fertilization by males
• ____________ species have been identified in 6
familes of lizards and 1 family of snakes
• Usually “test” this out by making reciprocal skin
grafts as…
…all young produced are genetically identical
to the the mother so there would be
no immune reaction and graft
would be
retained
• Common among whiptail lizards…especially
“hybrid” species
Parthenogenesis…con’t
• These hybrid species usually still found within
distribution of the two _________ “parent” species
distribution
• More commonly found where major ____________
(like floodplains) occur…with the disruptions being
frequent and “short-term” isolation allowing of a just
a few members of each “parent” species
• Because all from the hybrid species can reproduce,
they have twice the ______________ of the bisexual
species being a pathenogenetic species. Thus,
when a disturbance wipes out a large segment of the
lizard community…the parthenogenetic species can
repopulate the recovering habitat faster than the
parent species
Ectothermy – Chapter 14 PJH
(handout – inclass/take-home assignment)
• Dealing with dryness
• Coping with cold
• Vertebrate comparisons:
a) metabolic rates
b) adult body masses
c) efficiency of biomass conversion
chuckwalla
Foothill yellow-legged frog