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AMHIBIAN AND REPTILE REPRODUCTION
COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION
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AMHIBIAN AND REPTILE REPRODUCTION
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
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AMHIBIAN AND REPTILE REPRODUCTION
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 Jefferson’s/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
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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 Internal—Why??? 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 .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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Perhaps the most important development allowing
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 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 ( 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 Hews’s 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
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