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Amphibian Reproduction

Herpetoculture

Pensacola Jr College

Amphibians vs. Reptiles

w Major difference is egg structure:

• Anamniotic eggs – no shell, require moisture, produce larval form – amphibians

• Amniotic eggs – have shell and embryonic membranes, resistant to drying out, protect embryo, stores wastes, produce adult form - reptiles

Amphibian Urogenital System

w Excretory System

w Reproductive System

Excretory System

w Kidney types:

• Pronephric = drains coelom

• Mesonephric = filters wastes from BOTH coelom and blood

• True nephritic = extracts wastes from bloodstream only

w Amphibian larvae have pronephric kidneys, adults have mesonephric kidneys

Reproductive System

w Ovaries vs. testes:

• Development affected by hormones

• Development influenced by temperature

• Potential to be male OR female present in most amphibians

w Fat bodies associated with gonads, supplies energy

Reproductive System (cont’d)

w Ovaries

• Produce from 1 to thousands of oocytes at a time under influence of pituitary, squeeze out into peritoneal cavity

w Testes

• Located near kidneys, produce sperm under pituitary influence

• Rudimentary ovary often nearby

Reproductive System (cont’d)

w Female ducts:

• Oviduct covers egg with jellylike material

• Oviduct and ureter may be united through much of length

w Male ducts:

• Mesonephric ducts carry both sperm and excretory wastes

Amphibian Urogenital Tract

Reproductive Biology

w Mating / fertilization

w Embryo development

w Parental investment

w Sexes of population

w Breeding seasons and habitats

Amphibian Mating/Fertilization

w External fertilization

• Sperm fertilizes egg outside of female’s body

• Eggs / sperm laid at same time

• Amplexus used in anurans

• Found in all anurans except tailed frog

• Found in primitive salamander families

Amplexus

Mating/Fertilization (cont’d)

w Internal fertilization

• Spermatophore = packet with pedestal and sperm bubble deposited by male, picked up by female – advanced salamanders

• Cloacal kiss = press cloacas together for sperm transfer – some salamanders

Spermatophore

Mating/Fertilization (cont’d)

w Internal fertilization

• Copulatory organ = male has penetrating sperm delivery organ – tailed frogs and all caecilians

w Sperm may be stored up to years in spermatheca in female for later fertilization

Embryo development

w Oviparous = egg laying – most amphibians

w Ovoviviparous = retention of eggs/embryos in oviduct, young nourished by yolk sac – a few frogs & salamanders

w Viviparous = retention in oviduct, young nourished by oviduct – many caecilians

Egg laying

w Oviparous species

w 1 to 25,000 laid – species dependent

w Laid singly, in clusters, in strands – species dependent

w Laid in a variety of moist environments – species dependent

Giant Salamander Eggs

Tailed frog eggs

Woodhouse’s Toad eggs

Wood Frog eggs

Parental investment

w Little / none

• Many eggs with low survival

w Paternal care (external fert.)

• Clutch guarding

• Leg carrying of clutch

• Vocal sac brooding

• Tadpole carrying (on back)

Parental investment (cont’d)

w Maternal care (internal or external fert.):

• Internal development (ovoviviparous or viviparous)

• Pouch carrying of clutch

• Epidermal carrying of clutch

• Gastric brooding

• Deposit and return to provision with food (unfertilized eggs)

Sexes of populations

w Bisexual = male and female present, sperm+egg=embryo

w Gynogenesis = females only, mitosis without separation then meiosis, sperm needed to activate embryo

w Parthenogenesis = females only as above, self-activate

Breeding season/habitat

w Breeding season controlled by photoperiod, temperature, humidity, food availability

w Breeding habitats:

• Permanent bodies of water

• Temporary bodies of water

• Out of water in moist situations