Herp Reproduction
Animal Breeding
Pensacola Jr College
Amphibian
Reproduction
w Similar to fishes, widely
varying strategies
w Fertilization:
• Caecilians – internal with
phallodeum
• Salamanders – external, or
internal with spermatophore
• Anurans – external with
amplexus
Repro Tracts
Caecilians:
phallodeum
Salamanders: spermatophore
Anurans: amplexus
Amphibian
Reproduction
w Development – oviparous,
ovoviviparous, or viviparous
w Sex determination:
• Genetic and environmental
• May have distinct sexes
• May change sex thru lifespan
• May have all female groups –
gynogenesis / parthenogenesis
Amphibian
Reproduction
w Sex identification:
• Caecilians – shape of
cloacal opening
• Urodels – males typically
larger and more colorful; breeding behaviors
• Anurans – males typically
smaller, nuptial pads, vocalizations, breeding behaviors
Reptile
Reproduction
w Internal fertilization:
• Single penis in turtles /
crocs
• Hemipenes in squamates
• Cloacal kiss in tuataras
w Mostly oviparous (some
squamates live-bearing)
w Distinct sexes or all female
populations / species
Box Turtle penis
Kingsnake
hemipenes
Iguana hemipenes -
retracted
Reptile
Reproduction
w Temperature dependent sex
determination (no sex chromosomes) in all crocs, many turtles, some lizards
Female Repro Tract
w Symmetrically paired ovaries
with extensive vitellogenesis
w Oviducts
w Uterus
• Thick and muscled
• has eggshell glands
• Secretes eggshell membrane
• Retains eggs or has placenta
w Vagina
Female Repro Tract
w Lizards: ovaries may be
symmetrical or not
w Snakes: right ovary larger
and anterior to left ovary
w Crocs: 2 part uterus
• First part similar to other
reptiles (egg membrane deposition)
• Second part has glands for
calcareous eggshell
Female Repro Tract
w Hormonal controls mostly
similar to mammals
w Addition of arginine
vasotocin (AVT):
• Produced by hypothalamus /
posterior pituitary
• Stimulates uterine
contractions for egg-laying or parturition
Male Repro Tract
w Paired testes (do not
descend)
w Epididymides
w Single vas deferens
w Penis or hemipenes held
internally within genital cavity
w No accessory sex glands
Repro Tracts
Sex Identification
w Turtles:
• Males have longer tails
• Males have longer front
claws
• Males have concave plastron
w Lizards:
• Males usually visually
dimorphic (color, ornaments)
• Males have enlarged postanal
scales and femoral pores
• Probing not recommended
Turtle Sexing
Sex Identification
w Snakes:
• Males may have longer tail
with thicker base (for hemipenes)
• Sexing by palpation in young
snakes
• Sexing by metal sexing
probes in adult (3 – 6 scales in females and more than 12 scales in males)
Sexing Juvenile
Snakes
Sexing Adult
Snakes: probes
Lubricated probe
in cloaca
Rotate forward
first
Move probe into
tail until stops
Female depth
Male depth
Sex Identification
w Crocodylians:
• Larger males at any age
• Only gharials are otherwise
dimorphic (growth on snout tip in males)
Male gharial with
ghara
Temperature
Dependent Sex Determination (TDSD)
w Most studied in American
alligator and saltwater croc
w Two pivotal temps in crocs
TDSD Case Study:
The American Alligator
w Incubation at 30oC:
• All females
• Hatch at 74 days
w Incubation at 33oC:
• All males
• Hatch at 62 days
w Incubation at 34.5oC:
• All females, fast hatch
TDSD Control
Hypotheses
w Sex-determining genes?
• No known chromosome
differences
• Perhaps a gene switched on
or off by temperature?
w Sex hormones?
• Evidence through experimentation
TDSD Experiments
w Inject estrogen into eggs
incubated at male temps à females
w Inject estrogen inhibitors
into eggs incubated at female temps à males
w Inject testosterone into
eggs incubated at female temps à STILL females
Sex Steroid
Synthesis (simplified)
Enzymes Involved:
w 3B-HSD
• Produced in adrenal gland at
both male and female incubation temperatures
w Aromatase
• Produced in gonads of
embryos only at low and high temperatures in crocodylians
• Still questionable factor