Lizards & Snakes & Tuatara Part III

1. 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.

2. 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

3. 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 Proteinases Hyaluronidase L-amino acid oxidase Cholinesterase Phospholipases Phosphatases Basic polypeptides

4. Point: Data from W. Hayes, Loma Linda U.

5. s. Pacific rattlesnake cottonmouth Point: Data from W. Hayes, Loma Linda U.

6. 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

7. Sit-and-wait Cruising forager Widely foraging ? • Endurance • Sprint speed • Daily energy expenditure • Size of home range • Reproduction (relative mass of clutch) • Risk of predation ? ? intermediate ? ?

8. 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

9. 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

10. 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)

11. SIMPLE COMPLEX COMPOUND GULAR FANS Simple Compound  Complex   

12. Green anole (Anolis carolinensis) Gular fan…extended sometimes known as the ____________ Brown anole (Anolis sagrei)

13. A B C Fig. 13-12, p354 PJH

14. Green Anole behavioral displays A • ________________________MALE response to intruder to territory a) head bob b) dewlap extended c) nuchal & dorsal crests d) eyespot expanded • __________________intruder in close proximity and is a MALE a) head bob b) dewlap extended c) nuchal & dorsal crests d) eyespot f) facing • _____________ MALE “posturing” for female a) head bob b) head high c) dewlap extended d) no nuchal or dorsal crests e) no eyespot B C

15. 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)

16. 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

17. 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

18. 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