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COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION PowerPoint Presentation
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COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION

COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION

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COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION

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  1. COMPARE/CONTRAST AMHIBIAN AND REPTILE REPRODUCTION

  2. 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.

  4. 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

  5. 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

  6. 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

  7. 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

  9. 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

  10. 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

  11. 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

  12. 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)

  13. 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

  14. 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

  15. 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

  16. Crocodile Reproduction • All species show parental care • Mating activities of Alligator • Amazing recovery due to high reproductive rate Fig 9-10