Amphibian
Physiology
Herpetoculture
Pensacola Jr College
What is
physiology?
w The study of the functions
and processes of life (as opposed to structure)
w Geared towards maintenance
of homeostasis
State of stability,
equilibrium
w Dependent especially on
endocrine / nervous systems
Amphibian
Endocrine System
w Thyroid glands metabolism
w Parathyroid glands mineral
metabolism
w Adrenal tissue stress
responses, adrenaline
w Pancreas blood sugar
w Pituitary gland
reproduction
w Gonads egg/sperm
production and breeding
Amphibian nervous
system
w Central nervous system
Cerebral hemispheres of
brain are primarily olfactory centers
10 pairs of cranial nerves
(vs. 12 in higher vertebrates)
w Autonomic nervous system
Simpler than higher
vertebrates but same pattern
Nerves control other systems
Receptor Organs
w Lateral line system
In fish and larval / aquatic
amphibians only
Neuromast cells are
clustered in rows of pits on head / body
Respond to low freq
vibrations
w Cutaneous receptors
Well developed, respond to
mechanical stimulation
Tadpole w/ lateral
line
Lateral line pit
(SEM)
Receptor Organs
(contd)
w Ear
Only strongly developed in
those which can make sounds
Some salamanders sense
ground-borne vibrations through lower jaw / forelimbs
Frogs and toads (except
burrowers) have tympanic membrane on body surface
Receptor Organs
(contd)
w Eye
First eyelids anurans
First lacrimal duct to drain
excess fluids from eye
Lens hard and fixed like
fishes (move it to focus)
Photoreceptor cells rods
(b & w) and cones (color) present
w Pineal gland - photoreceptor
Receptor Organs
(contd)
w Chemical receptors
Spread throughout skin
unlike higher vertebrates
Scattered taste buds
Olfactory organs inside
nasal passages
Jacobsons organ olfactory
concentrated receptors in sac, first found in land amphibians
Metamorphosis
Amphibian Metamorphosis
w All amphibians undergo
changes between larvae and adult forms
w Larvae are all aquatic and
herbivorous
w Adults are aquatic or
terrestrial, and carnivorous
Amphibian Larvae
w Thin fragile vascularized
skin
w External gills
w Lidless eyes
w Muscular trunks and tails +
dorsal / ventral tail fins for swimming
w Cartilaginous skeleton
Amphibian Larvae
(contd)
w Well-developed lateral line
system
w Fishlike (single loop)
circulatory pattern
w Elongated digestive tract
Urodel
metamorphosis
w Larval salamanders and caecilians
are mini-adults except for gills and tail fins
w Paedomorphosis = retention
of juvenile traits in adults
Occurs in many aquatic
salamanders
w Terrestrial forms have
limited metamorphosis
Salamander Larva
Anuran tadpoles
w Tadpoles look nothing like adults,
concentrated for maximum feeding / growth
w Hind limbs visible late
w Front limbs begin to form
under operculum
w Have oral disc with keratin
scrapers and sensory bumps
w No teeth or tongue
Tadpole
Tadpole Mouth
Parts
Anuran Metamorphosis
w
Change skin structure
w Develop eyelids
w Lose lateral line system
w Resorb gills / develop lungs
w Shorten digestive tract
w Modify feeding mechanism
w Modify muscle and skeleton
Anuran
Metamorphosis (contd)
w Ossify skeleton
w Reconfigure circulatory
pattern for double circulation
Metamorphosis -
Control
w Thyroid gland produces
thyroxine
w Thyroxine triggers start of
metamorphosis
w Thyroxine and prolactin
(from pituitary) control the necessary changes
Metamorphosis
Control (contd)
w Body tissues in larvae are
insensitive to thyroxine until time of metamorphosis
w Triggers to tissue
sensitivity to thyroxine:
Increasing temperatures
Decreasing crowding