Transcript Amphibians

Amphibians
Movement onto Land
• In order for animals to live on land they:
– Need to support their own weight (deal with
gravity)
– Resist drying
• Important during reproductive stages (egg) since
they can not do anything actively to prevent water
loss
• Constant problem in daily life
– Deal with rapid temperature changes
– Be able to extract oxygen from air
• living a double life
• frogs, toads, salamanders, and caecilians
• either moves in and out of water or spends
part of life cycle in water
• Tetrapods – presence of four muscular
limbs and feet with toes and fingers (digits)
Phylogenic Relationships
• 400 million year old “Ichthyostegalia”
• From an evolutionary point of view, the
Sarcopterygians were the last of the fishes. The next
chordates to evolve were true tetrapods and thus were
considered Amphibians. By the end of the Devonian
period, there was an animal present that had the
rudiments of the Amphibian structure. This animal was
an Ichthyostegalia. The main difference between this
animal and the lobe-finned fishes was the
development of the girdles; skeletal bones that
connected the axial skeleton of the vertebral column
with the bones of the lateral appendages. Other
skeletal strengthening involved the rib cage and the
cranium. The Ichthyostegalia still retained the caudal
fin (with fin rays) and scales of its fish ancestors. The
median fin still remains in the larval forms of the
Amphibians.
Ichthyostegalia
Survey of Amphibians
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- Everywhere but Antartica and many
oceanic islands
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Order Caudata – salamanders
http://www.npwrc.usgs.gov/narcam/idguide/
atigrin.htm
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Tail throughout life
Moist forest litter and have aquatic larvae
Family plethodontidae – eggs laid on land,
young hatch as minature adults
Order Caudata – salamanders
• The Gray Tiger Salamander (Ambystoma tigrinum
diaboli) are easily recognized with their dark green to
gray background speckled with tiny black dots. It breeds
in the early spring, migrating to ponds as soon as the ice
on them begins to melt.
Order Caudata – salamanders
• In the Blotched Tiger Salamander (Ambystoma tigrinum
melanostictum) the background color is dull yellow and is lighter
than in the Gray Tiger Salamander. The dark markings are also
larger but usually take up less area than the background color.
These irregular markings often form a network-like pattern. The
Blotched Tiger Salamnader is also an early spring breeder.
Salamander eggs
Family Plethodontidae
265 species of lungless aquatic and terrestrial salamanders
• lungs were lost in forms inhabiting cool, swift running streams; disadvantage
of too much buoyancy
• Small size of terrestrial species high surface/volume ratio provides adequate
surface for gaseous exchange to take place across the skin.
• absence of lung and hypobranchial apparatus leaves room for a large
protrusible tongue; especially well-developed in the bolitoglossines [fig 9-2]
Family salamandridae
– newts most life in water and retain a caudal fin largest 65 cm –
hellbender
Kissing a Hellbender - YouTube
Most internal fertilization
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Males drop pouch females pick up with the cloaca and store sperm
in special pouch
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Eggs fertilized as pass through cloaca
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Larvae similar to adults but smaller
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Some posses external gills, tailfin
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“incomplete metamorphosis” and are paedomorphic – become
sexually mature while still showing larval characteristics
Hellbenders
• Where Do They
Live?
• Since
hellbenders
spend their
entire lives in
water they need
to have streams
that are cool
enough and
which have
enough oxygen
to sustain them.
• Hellbenders are not the largest salamanders in the world, but
they're pretty close. The largest hellbender ever recorded was just
over 29 inches long! Hellbenders can weigh up to about 4 - 5 lbs.
Their close relatives in Japan and China, salamanders in the
genus Andrias, can reach lengths over 5 feet and may weigh as
much as 100 lbs.
• Hellbenders have a flat body and head, a large, very keeled tail
that helps to propel them through the water, and tiny eyes. They
have fleshy folds of skin along the sides of their body which help to
take in oxygen from the water. The arms and legs are very large
and muscular and they have 5 fingers on their rear feet and 4 on
the front feet. Hellbenders can range in color from dull brown or
gray to bright orange or red. They usually have some sort of
darker spots or blotches on their bodies, but the belly is usually
only one color. If you pick up a hellbender you will find out very
quickly that they are extremely slimy! This makes them very
difficult to catch and to handle, but it probably serves the purpose
of keeping them free from infections and may help to cut down on
the friction of the very fast flowing water they live in. Hellbenders
do have many, tiny teeth, but they rarely attempt to bite. I have
handled hundreds of hellbenders and I've only been bitten once -and I deserved it. The bite of a hellbender is not venomous!
The skin secretions are toxic to other animals, but as long as you
don't try to eat a hellbender, you're ok.
Hellbenders
Order Gymnophiona
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The Caecilian - YouTube
Caecilians
Gym – naked, ophineos – like a snake
Wormlike burrowers, feed on worms and other
invertebraes in soil
Skin covers eyes/ nearly blind
Internal fertilization
Order Gymnophiona
Order Gymnophiona
Order Anura (salientia)
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A- without, nura – tail
Frogs and toads
Most moist environments
External fertilization
Larvae typically aquatic
Larvae herbivores and posses a proteinaceous –
beaklike structure used in feeding
Toad – dry, worty skin
COMPARISONS OF SPECIES
1. What is the difference between frogs and toads?
• Frogs have:
smooth or slimy skin
• Toads have:
warty and dry skin
• strong, long legs
webbed hind feet
• stubby bodies with short
hind legs
• two bulging eyes
• paratoid glands behind
eyes
• lay eggs in clusters a
group of frogs is called an
ARMY of frogs
• lay eggs in long chains
a group of toads is called
a
KNOT of toads
Anura
Evolutionary Pressure
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Water – support water buoyant properties
exchange gases and face osmoregularity
problems as fresh water fish
– Land – support against gravity exchange
gases with air
• Loses water to air
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during extensive periods of heat or drought,
frogs can enter a period of dormancy similar to
hibernation called estivation
External structure and locomotion
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Skin – protects against infective microorganisms,
uv light, dessication, and injury
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Used as gas exchange, temperature regulation,
absorption and storage of water
No scales, feathers or hair
Secretions aid in protection, keep skin moist and
sticky substance that helps male adhere to female
during mating and produce toxic chemicals
Chromatophores
Support and movement
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Skull lighter to be supported out of water
Pelvic girdle – 3 bones for support on land
(ilium, ischium, pubis)
Limbs – four (tetrapod); some are legless
Unlike frogs and toads, salamanders and newts have
elongated bodies, more like the earliest fossil amphibian.
They move with a side-to-side (S-shape) motion like that of
a fish.
Nutrition and the digestive system
– Most eat a variety of small invertebrae
– Anurans – mammals, small birds, and other
anurans
– Salamanders – just use tongue to capture
prey
– Anurans and plethodontid salamanders use
tongue, jaw in a flip-n-grab mechanism
– .05 - .15 seconds
– eyes sink downward during swallowing to help
force food to the esophagus
Circulation
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The circulation system of amphibians
shows remarkable adaptations for a life
divided between aquatic and terrestrial
habits
Adults – 3 chambered heart
Circulation to lungs and skin separated
from circulation to rest of body; makes
respiration more efficient
Larvae – 2 chambered heart
Gas Exchange
Air contains 20X more oxygen than water does
– Skin functions as a respitory organ – many capillarie beds
and moist skin
– Cutaneous respiration – gas exchange across the skin
• Allows frog to spend winter in mud at bottom of pond
– 30 -90% of gas exchange occurs across the skin,
• mouth and pharynx exchange gas (Buccal) also – 1-7% of gas
exchange
– plethodontid salamanders – no lungs
– during metamorphosis, the gills are reabsorbed, pharyngeal
slits close and the lungs become functional
– No lungs in early stages
Gas exchange occurs across the thin, moist skin of
amphibians. Unlike other tetrapods, amphibians have little
waterproofing with keratin. There are many mucous and
poison glands in the skin.
Frogs ventilate their lungs
by a positive pressure
system. Air is forced into
the lungs when the floor of
the mouth is raised. Air is
expelled by contraction of
body wall muscles and
elastic recoil of the lungs.
Temperature Regulation
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Ectothermic – depend on external head
source to maintain body temperature.
Temperature regulation is behavioral
(water, sun)
Nervous & Sensory
– Similar to the other vertebrates
– Lateral-line system similar to fish
• Low frequency vibrations in water and movements of water
relative to the animal
• On land less important
– Chemoreceptors
– Vision important – sight feeders movement of prey
• Exception? Caecilians
– Eyes in front – depth percetion
– Color vision – unknown
– Sounds – mating – highfrequency, low – warning
approaching predators
Amphibians were the
first vertebrates to
use the ear for
hearing. All
vertebrates have an
inner ear with
semicircular canals
and other structures
for motion and
gravity detection;
tetrapods have at
least one middle ear
bone for conduction
of sound waves from
the tympanic
membrane (ear
drum) to the inner
Excretion & Osmoregulation
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Excrete ammonia or urea
Water update across skin
Protective covering to reduce water loss
No scales; smooth skin, moist with
many glands
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Skin color due to chromatophores located
in dermis
Reproduction
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Dioecious
Fertilization usually external
Eggs develop in water or moist environment
10% salamanders have external fertilization
all caecilians have internal fertilization
reduction of competition – larvae/adult
breeding – rainy season, spring/summer
amplexus – male dorsal to female – mating
position
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male releases sperm as female releases
Regeneration found in all
Regeneration In Urodeles
• Amphibians accomplish
fertilization of their eggs in a
variety of ways. External
fertilization, employed by most
frogs and toads, involves a
male holding a female in a pose
called amplexus. In amplexus,
the male releases sperm over
the female's eggs as they are
laid. Less risky is the method
employed by many
salamanders whereby the male
deposits a packet of sperm
called a spermatophore onto
the ground. The female then
pulls it into her cloaca where
fertilization occurs internally. By
contrast, caecilians and tailed
frogs use internal fertilization
just like reptiles, birds and
mammals. The male deposits
sperm directly into the female's
cloaca via an intromittent organ.
Although most frogs and toads (Order Anura) lay their externally fertilized eggs
in water and leave them to hatch into tadpoles and develop on their own, some
species exhibit a great deal of parental care, as in the examples shown here.
There are also species that lay eggs on land and stay with them
until they hatch. Larval development is completed within the egg.
Caecilians (Order Apoda) are limbless, predatory,
burrowing amphibians. All have internal fertilization. Some
stay with their eggs; others give birth to live young with
nourishment provided by the mother during development.
Gastric Brooding Frog
• The gastric brooding frog
of Australia swallows her
fertilized eggs. The
tadpoles remain in her
stomach for up to 8
weeks, until finally
hopping out of her mouth
as little frogs. During the
brooding period, gastric
secretions cease-otherwise she would
digest her own offspring.
The Gastric Brooding
Frog was found in
Australia. Sadly, not long
after their discovery they
dissapeared and are now
believed to be extinct.
Surinam Toad
http://www.youtube.com/watch?v=mZ7b4spjXhw
Vocalization
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Sound mainly for reproductive of
male anurans
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Attract females warn males the
territory is occupied
Release calls – given by males if
male attempts amplexus on another
male
Distress call – pain or seized by
predator
Parental Care
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Increases the chances of any one egg
developing
Carry on back
In stomachs
In vocal pouch
Metamorphosis
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A series of abrupt structural, physiological,
and behavioral changes that transform a
larva into an adult
Crowding and food availability can
influence the time required for
metamorphosis (mostly due to hormones)
Tail is reabsorbed, gills are lost, caudal fin
is lost, reproductive structures develop,
skin thickens, limbs and lungs develop,
chanes in head and digestive tract.
Salamanders (Order Caudata) have internal fertilization
and many species lay their eggs in water. Like anurans,
they have an aquatic, gilled larval stage. No vocal cords
Amphibians in peril
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Disappearing at an alarming rate
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Mining, drilling, industry, destroying habitat, acid
deposition and uv radiation, ph levels in water,
• Three sets of evolutionary changes in amphibian
lineages allowed movements onto land. Two of these
occurred early enough that they are found in all
amphibians. One was the set of changes in the skeleton
and muscles that allowed greater mobility on land. A
second change involved a jaw mechanism and movable
head that jaw-muscle arrangement that permitted
rhipidistian fishes to snap, grab, and hold prey was
adaptive when early tetrapods began feeding on insects
in terrestrial environments. The third set of changes
occurred in the amniote lineage the development of an
egg that was resistant to drying.
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Goliath Frog
from east Africa.
World’s largest
Anuran.
Many brought into the
USA for zoos and
jumping competitions.
• No breeding. None
survive.
• Recently bred in
Europe by hobbyist in
3 x 1 m box.
Smallest Frog
Funny Frogs
• Top 10 Coolest and Weird Frogs –
YouTube
• Unbelievable Funny FROG Video EVER
Seen 2012 - YouTube