Post on 18-Jan-2016
Lizards & Snakes & Tuatara Part III
VERTEBRATE ZOOLOGY (VZ Lecture19 – Spring 2012 Althoff - reference PJH Chapters 13 &
14)
Photo: Steve Huskey
Data from W. Hayes, Loma Linda U.
• 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 preyb) 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
Proteinases
Hyaluronidase
L-amino acid oxidase
Cholinesterase
Phospholipases
Phosphatases
Basic polypeptides
Venom components & effects
Tissue destruction
Increases tissue permeability
Attacks wide-variety of substrates, tissue destruction
Unknown
Destroys cell membranes
Breaksdown ATP, etc.
Blocks neuromuscular transmission
Data from W. Hayes, Loma Linda U.
Point:
Data from W. Hayes, Loma Linda U.
Point:
s. Pacific rattlesnake
cottonmouth
• Three basic foraging modes observed among lizards (summarized from Table 13.5, p384 PJH):
1) sit-and-wait
2) curising forager
3) widely foraging
Foraging Behaviors: Squamates
Sit-and
-wait
• Endurance• Sprint speed• Daily energy
expenditure• Size of home
range• Reproduction
(relative mass of clutch)
• Risk of predation
Cruisi
ng for
ager
Widely
fora
ging
?
?
intermediate
?
?
?
• 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
Risks and Predator-Escape Mechanisms
• 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
Caudal Autotomy of Squamates
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 Ricaillustrated in PJH Fig. 13-11, pg353)
SIMPLE COMPOUND COMPLEX
Simple
Compound
Complex
GULAR FANS
Green anole(Anolis carolinensis)
Gular fan…extendedsometimes known
as the____________
Brown anole(Anolis sagrei)
Fig. 13-12, p354 PJH
C
B
A
Green Anole behavioral displays
• ________________________MALE response to intruder to territorya) head bob b) dewlap extended c) nuchal & dorsal crests d) eyespot expanded
• __________________intruder in close proximity and is a MALEa) head bob b) dewlap extended c) nuchal & dorsal crests d) eyespot f) facing
• _____________ MALE “posturing” for femalea) head bob b) head high
c) dewlap extended d) no nuchal or dorsal crests e) no eyespot
A
B
C
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 ratesb) adult body massesc) efficiency of biomass conversion
chuckwallaFoothill yellow-legged frog