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