COMPARE/CONTRAST

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COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION
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COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION

• Amphibian Reproduction
• Complex Life Cycles
• Aquatic Larvae
• Gelatin Eggs

• Reptile Reproduction
• Simpler Life Cycles
• Amniotic Eggs
• Released From Aquatic
• Environments

3
COMPARE/CONSTACT AMHIBIAN AND REPTILE REPRODUCTION

• Amphibian Reproduction
• Complex Life Cycles
• Aquatic Larvae
• Gelatin Eggs

• Reptile Reproduction
• Simpler Life Cycles
• Amniotic Eggs
• Released From Aquatic
• Environments

Remember these are generalities.
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Caecilians

• Internal Fertilization via phalodeum
• Eggs attended by females
• Larvae hatch out at a fairly advanced stage
• Some show direct developments
• Overall remain poorly studied

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Salamanders

• Few primitive forms with external fertilization
• Internal Fertilization via spermatophore
• Variety of Parental Care
• Lay and Abandon
• Female Guards Eggs
• Larvae are basically aquatic adults
• Paedomorphosis is common result of Heterochrony
• Local Jeffersons/Smallmouth Hybrids
• Behavior Heavily Studied

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Salamander Sexual Behavior

• Variety of Male/Male Interactions
• Direct Aggression
• Mate Guarding (Amplexus)
• Lekking
• Females Choose Good Eaters
• Use Many Chemical Cues
• Alternate Male Strategies
• Satellite Males
• Spermatophore Dumping
• Result is Intense Sexual Selection
• Selection by one gender for a trait in the other.
  

14-5
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Frogs

• Most have external fertilization
• Tadpoles use very different resources than adults
• Variety of Parental Care
• Lay and Abandon
• Nest Building
• Female Guarding
• Male Guarding
• Adult Assistance
• Maturation of Larvae Depend
• on Reaching Minimum or Maximum Size

8
Frog Sexual Behavior

• Variety of Male/Male Interactions
• Direct Aggression
• Amplexus
• Inguinal (Primitive)
• Axillary
• Cephalic
• Long-term Guarding
• Chorusing
• Resource (Oviposition Sites) Defense
• Explosive Breeding
• Alternate Male Strategies
• Satellite Males
• Female Mimics

8-2 14-8 14-25
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Reptilian Reproduction

• Fertilization is Always InternalWhy???
• Where Do Males and Females Come From?
• Amniotic Egg Allows Divorce From Water
• Many Amphibians Have Found Other Ways to Do This
• Allows Reptiles to Cary The Pond With Them
• Desert Areas Are Very Important For Reptile
  Diversity
• Many Species Are Viviparous
• Intense Sexual Selection
• Presence of Unisexual Hybrid Species

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Temperature vs Genetic Sex Determination

• In many reptiles (and some amphibians)
• incubation temperature dictates sex of young
• Turtles lower temps produce males
• Some lizards get opposite
• Crocs, Turtles, and some lizards get females at
  extremes
• Can result in dramatic difference in sex ratios
• How will global warming impact this trait?
• Why did it evolve?
• How does it work
• Exact mechanism is unknown
• Enzyme that converts steroids may be temperature
  dependent.
• At male temperature T DHT
• At female temperature T E

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Sex Cycles

• Associated
• Seasonal Breeding
• Gonads Active During Mating
• Ex Most Local Herps
• Disassociated
• Seasonal Breeding
• .Gonads Active At Another Time
• Requires Sperm Storage
• Red-sided Garter Snakes
• Crotaline Snakes
• Continuous
• Constant Breeding
• Gonads Active All The Time
• Tropical Species

Fig 9-4
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Amniotic Egg

• Perhaps the most important development allowing
• vertebrates to invade dry land
• Outside covered by membranous (sometimes
  calcareous) shell
• 4 extra-embryonic membranes
• Yolk Sac
• Highly Vascularized
• Also present in amphibians
• Amnion
• Allentois
• Stores uric acid
• Chorion
• Latter 2 fuse into Chorioallentoic Membrane
• Responsible for gas exchange

(Fig 13-16 from Hickman et al, 1986 Biology of
Animals)
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Asexual Species

• Multiple species of squamates
• 30 Species Lizard
• 1 Snake
• Widely spread in flower pots
• 1 female starts a new population
• Best studied among Apidoscelis (formerly
  Cnemidophorus)
• Result of recent (100-1000 years) hybridization
• Reproduction via Parthenogenesis
• No meiotic Reduction
• Psuedocopulation between females
• Increases gonadal activity

Fig 9-1
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Turtle Reproduction

• Recognize males by convex plastron
• Mating accomplished via penis
• Competition between males common
• Male tortoises attempt to flip rivals
• Only share burrows during mating
• Larger males are successful in aquatic species
• All but 1 species lays eggs on dry land
• Recent efforts indicate these nests are not
  adequately protected

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Snake and Lizard Reproduction

• Most are viviparous except
• Natricidae
• Crotalinae
• Elapidae
• Some iguanas
• Male/male competition
• Direct competition
• Resource defense
• Diana Hewss work on Uta
• Lekking
• Mate guarding (ex Lacerta)
• Sperm competition
• Alternate male strategies (Uta)
• Intermittence via hemipenes
• Paired structures on cloaca
• L and R tracts are separate

Fig 14-10 Tree Cover 9-5
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Crocodile Reproduction

• All species show parental care
• Mating activities of Alligator
• Amazing recovery due to high reproductive rate

Fig 9-10