COMPARE/CONTRASTAMHIBIAN AND REPTILE REPRODUCTION

Amphibian Reproduction

•Complex Life Cycles

•Aquatic Larvae

•Gelatin Eggs

Reptile Reproduction

•Simpler Life Cycles

• Amniotic Eggs

•Released From Aquatic Environments

COMPARE/CONTRASTAMHIBIAN AND REPTILE REPRODUCTION

COMPARE/CONSTACTAMHIBIAN 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.

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

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

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

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

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

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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

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

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

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)

•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

Asexual Species

Fig9-1

•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

Turtle 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

Snake and Lizard Reproduction

Fig14-10Tree Cover9-5

•All species show parental care

•Mating activities of Alligator

•Amazing recovery due to high reproductive rate

Crocodile Reproduction

Fig9-10