Amphibian reproduction

1. Amphibian ReproductionAmphibian Reproduction

2. AnamnioticAnamniotic eggs – eggs – no shell, require no shell, require moisture, moisture,
produce larval form – amphibians produce larval form – amphibians
Amniotic eggsAmniotic eggs – – have shell and embryonichave shell and embryonic
membranes, resistant to membranes, resistant to drying out, protect drying out, protect
embryo, stores wastes, produce adult form - embryo, stores wastes, produce adult form -
reptilesreptiles

3. Reproductive SystemReproductive System
Ovaries vs. testes:Ovaries vs. testes:

Development affected by hormonesDevelopment affected by hormones

Development influenced by temperatureDevelopment influenced by temperature
Potential to be male OR female present in most Potential to be male OR female present in most
amphibians amphibians
Fat bodies associated with gonads, supplies energyFat bodies associated with gonads, supplies energy
•

4. OvariesOvaries
Produce from 1 to thousands of ocytes atProduce from 1 to thousands of ocytes at a time under a time under
influence of pituitary, squeeze out into peritoneal influence of pituitary, squeeze out into peritoneal
cavity. cavity.
TestesTestes
Located near kidneys, produce sperm under pituitary Located near kidneys, produce sperm under pituitary
influence influence
Rudimentary ovary often nearbyRudimentary ovary often nearby

5. Female ductsFemale ducts – –
Oviduct covers egg with jellylike material Oviduct covers egg with jellylike material
Oviduct and ureter may be united through much of Oviduct and ureter may be united through much of
length length
 Male ductsMale ducts
Mesonephric ducts carry both sperm and excretory Mesonephric ducts carry both sperm and excretory
wasteswastes

6. Amphibian Urogenital TractAmphibian Urogenital Tract
Mating / fertilization Mating / fertilization
Embryo development Embryo development
 Parental investmentParental investment
 Sexes of population Sexes of population
Breeding seasons and habitats Breeding seasons and habitats

7. Amphibian Mating/FertilizationAmphibian Mating/Fertilization
External fertilizationExternal fertilization
Sperm fertilizes egg outside of female’s bodySperm fertilizes egg outside of female’s body

Eggs / sperm laid at same timeEggs / sperm laid at same time
Amplexus used in anurans Amplexus used in anurans

Found in all anurans except tailed frogFound in all anurans except tailed frog
Found in primitive salamander families Found in primitive salamander families

8. Amphibian Mating/FertilizationAmphibian Mating/Fertilization
Internal fertilizationInternal fertilization - - Spermatophore = packet Spermatophore = packet
with pedestal and sperm bubble deposited by male, with pedestal and sperm bubble deposited by male,
picked up by female – advancedpicked up by female – advanced salamanderssalamanders
Cloacal kiss = press cloacas together for sperm Cloacal kiss = press cloacas together for sperm
transfer – some salamanders transfer – some salamanders

9. Egg layingEgg laying

Oviparous species Oviparous species
1 to 25,000 laid – species dependent 1 to 25,000 laid – species dependent
Laid singly, in clusters, in strands – Laid singly, in clusters, in strands –
species dependent species dependent
Laid in a variety of moist environments – Laid in a variety of moist environments –
species dependent . species dependent .

10. Reptile Reproductive Reptile Reproductive
SystemSystem

11. Gonads -Gonads -
Paired, in abdominal cavity Paired, in abdominal cavity
Snakes/legless lizards: one gonad anterior, Snakes/legless lizards: one gonad anterior,
one posterior one posterior
Snakes/lizards: gonads are sacs with lymph Snakes/lizards: gonads are sacs with lymph
cavitiescavities
Turtles/crocs/tuatara: gonads are solid structures Turtles/crocs/tuatara: gonads are solid structures
Fewer Graafian follicles at a time than in amphibiansFewer Graafian follicles at a time than in amphibians

12. Reptile Egg StructureReptile Egg Structure
1.1.Embryo Embryo
2.2.Amnion= cushion membrane Amnion= cushion membrane
3.3.Yolk sac= nutrition Yolk sac= nutrition
4.4.Allantois= waste sac Allantois= waste sac
5.5.Chorion= membrane immediately inside Chorion= membrane immediately inside
shell shell

13. Sexes of PopulationSexes of Population
Most are bisexual Most are bisexual
2.2.A number of lizard species have parthenogenetic A number of lizard species have parthenogenetic
populations or whole species. populations or whole species.
Some parthonogenetic females mate with males of Some parthonogenetic females mate with males of
related species, result is triploid sterile offspringrelated species, result is triploid sterile offspring

14. Embryo Development Embryo Development
Most reptiles are oviparousMost reptiles are oviparous
Eggs larger and more easily hidden in Eggs larger and more easily hidden in
terrestrial environment so can have terrestrial environment so can have
fewer eggs than amphibians fewer eggs than amphibians
Some lizards and snakes are ovoviviparous Some lizards and snakes are ovoviviparous
or viviparousor viviparous

15. Length varies by temperature Length varies by temperature
1.1.Sex of offspring dependent on incubation Sex of offspring dependent on incubation
temperature of clutch in many reptiles. temperature of clutch in many reptiles.
Pivotal temperature= produces 50% of each Pivotal temperature= produces 50% of each
sex sex
Turtles: males below the PT Turtles: males below the PT
Lizards: females below the PT Lizards: females below the PT
Crocodilians: two PTs, males in between the Crocodilians: two PTs, males in between the
two two

16. Methods of Reproduction Methods of Reproduction
in Mammals in Mammals

17. The three living groups of The three living groups of
mammals vary in their methods of mammals vary in their methods of
reproductionreproduction
Placental MammalsPlacental Mammals,, like the cat, are viviparous like the cat, are viviparous
Viviparity, or birth of live young, has independently evolved Viviparity, or birth of live young, has independently evolved
more than one hundred times in vertebrates However, more than one hundred times in vertebrates However,
many vertebrates retain the shelled egg laying method of many vertebrates retain the shelled egg laying method of
giving birth due to the nutrients provided by the shell and giving birth due to the nutrients provided by the shell and
passed to the embyopassed to the embyo. .

18. MonotremesMonotremes – –
are the most primitive living mammals. are the most primitive living mammals.
They have retained the reptilian oviparous They have retained the reptilian oviparous
method of reproduction and lay shelled method of reproduction and lay shelled
eggs. eggs.

19. MarsupialsMarsupials - - undergo a distorted undergo a distorted
version of viviparity. They give birth to version of viviparity. They give birth to
underdeveloped live young. When the underdeveloped live young. When the
young are born, they make their own way young are born, they make their own way
to the permanent brood pouch, or to the permanent brood pouch, or
marsupium .Development of the young is marsupium .Development of the young is
completed in the pouch.completed in the pouch.