Download Amphibians

Kingdom – Animalia
Phylum - Chordata
Class Amphibia
3 Orders
• Anura (Frogs & Toads)
• Caudata(Salamanders)
• Gymnophiona(Caecilians)
Movement onto Land
• Life began in the water, animals are made of
mostly water, and all cellular functions occur
in water.
• Invasion onto land required modification of
almost every system in the vertebrate body.
The Amphibian is an example of this
terrestrial transition.
• They are tetrapods-presence of 4 muscular
limbs and feet with toes and fingers
Accommodations to be considered
when moving to land
• Oxygen content
– Oxygen diffuses more readily in air then water
– 20 times more oxygen per unit volume in air
• Development of lungs
• Terrestrial animals use much less energy acquiring air
• Support
– Provides little support against gravity
• Requires the development of strong skeleton and
muscular limbs to get around
• Lighter skull w/jaw that can crush prey held in mouth
Accommodations to be considered when
moving to land
• Temperature regulation
– Air fluctuates in temperature more then water
– Amphibians are ectothermic-depend on external heat
sources to regulate body temp
• Requires (mainly) behavioral and physiological strategies to
protect themselves from thermal extremes
• Habitat diversity
– Diverse biomes to live in and adjust to
– Found on all continents except Antarctica and absent
from some oceanic islands
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Ectothermic
3-chambered heart (Double circulation)
Smooth skin, lacks scales (Desiccation if dry)
Cutaneous respiration
Lungs (Positive pressure mouth breathing)
Excretes urea
Lack claws on toes
Characteristics of
Class: Amphibia—on both sides
• Over 5,000 species
• Require a metamorphosis from water to land
during development
• Skin is thin and requires moisture
• Ectothermic—body temperature varies with
outside changing temperature (cold blooded)
• Eggs lack multicellular membranes or shells,
usually externally fertilized and laid in water
Order Gymnophiona
“caecilians”
• Limbless (naked snake)
• Tropical forests of South America, Africa, and
South East Asia
• Most species totally blind
• Mostly burrow or aquatic
• Carnivores
• All thought to have internal fertilization
• Some lay eggs (female guards), others develop
inside female
New caecilian:
click pic
Interesting meal!
Click
Order Caudata
“salamanders”
• Having a tail
• Some fully aquatic, fully terrestrial, or
amphibious
• Found in all North America, tropical areas
of Central and northern south America
• Carnivorous both as larva and adult
• Some have no lungs (respire through skin),
some keep gills
• http://srelherp.uga.edu/salamanders/inde
x.htm
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Salamanders
Newts (Efts)
Mudpuppies
Sirens
Click
Axolotl
Spanish Ribbed Newt
adapted from
http://gideon.k12.mo.us/teachers/jswilley/
htdocs/Classification%20of%20Animals.ppt
Click
Order Anura
“frogs and toads”
• Without tail
• Carnivores (adults) and herbivores (larvae)
• Some fully aquatic, fully terrestrial, or
amphibious
• Found in temperate and tropical regions
throughout the world except New Zealand
• http://srelherp.uga.edu/anurans/index.ht
m
Horror Frog
adapted from
http://gideon.k12.mo.us/teachers/jswilley/
htdocs/Classification%20of%20Animals.ppt
Body Plan
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Bilateral symmetry
Skeleton mostly bony
Most have small teeth
Segmentation-head normally distinct from
body
• Four limbs (except caecilians)
• Some have webbed feet
– no nails or claws, 4-5 digits
Skin
Click:
Rain
Frog
• Made of Keratin a tough protein that helps protect
against abrasions and water loss
• Moist
• Two layers—epidermis and dermis
• With many glands
– Granular glands- secretions are noxious or toxic to varying
degrees from species to species
– Some exhibit antibacterial, antifungal, and anticancer effects
– Mucous glands waterproof the skin
• Pigment cells—Chromatophores affect skin color and
color changes
Respiration
• Air is forced into the lungs with mouth muscles
[positive pressure]
• Air can be diffused through skin (cutaneous
respiration) and the inside of the mouth
(buccopharyngeal respiration)
• The majority of carbon dioxide is released through
the skin
• Sound is created by forcing air over vocal cords and
a large pair of sacs in the floor of the mouth
Circulation
• Closed system
• Origin of the Systemic and Pulmonary Circuits
– PULMONARY circulation- carries deoxygenated blood from heart
to lungs and oxygenated blood back to heart
– SYSTEMIC circulation-carries oxygenated blood from heart to
body and deoxygenated blood back to heart
• 3 chambered heart
– 2 atria
– 1 ventricle
– Spiral valve helps separate the flows of oxygenated vs
deoxygenated blood
In amphibians, the blood makes two passes through the heart.
Heart ---> lungs --> heart ---> body
Nutrition
Click!
• Carnivores feeding on insects, spiders, worms
slugs, snails, millipedes
– Bullfrogs may even feed on small mammals,
birds, and other anurans
• Many have a protrusive tongue is attached at
the anterior/front of the mouth- with sticky
secretions
• Eyes are pushed down against roof of mouth to
aid in swallowing
Digestion
• Complete digestive system
• Cloaca with vent (exit opening)
Excretion
• Tadpoles excrete as AMMONIA through gills and
kidneys like a fish
• ADULTS: 2 KIDNEYS- remove nitrogen waste from
blood and dilute with water to make urine
Adults worry about drying out so excrete as UREA
= less toxic than Ammonia & needs less water to
dilute;
• Urine flows through urinary ducts to CLOACA;
URINARY BLADDER (pouch off cloaca) stores urine;
BLADDER also stores water in dry periods (can
reabsorb water from urine)
Nervous System
• DORSAL SPINAL CORD covered
with bone (VERTEBRAE)
• SENSES:
– Smell—olfactory epithelium
– EYES- important in hunting and avoiding
predators; covered by transparent
NICTITATING membrane
– EARS- TYMPANIC MEMBRANE=eardrums
on side of head; sound receptors in inner
ear inside skull;
COLUMELLA-small bone transmits sound
between tympanic membrane and inner
ears
• BRAIN covered by skull (CRANIUM), about same size as fish
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MEDULLA OBLONGATA- controls autonomic body
organs, relays info from body
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CEREBELLUM-muscle coordination & balance
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OPTIC LOBES- process info from eyes and other senses
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CEREBRUM- higher thinking, learning, memory,
reasoning, integrates behavior
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OLFACTORY LOBES- for smell, larger than in fish
Reproduction
• Sexual with external fertilization
• In the spring, male frogs and toads vocally attract
females to mate with
• Eggs are laid in large masses and can be anchored to
vegetation, simply float in water, or laid under logs in
moist ground
– Packet of sperm may be left on vegetation and
then inserted by the female herself
– Male may force eggs to be evacuated from the
female as he discharges his sperm over the eggs—
amplexus
Click!
Development
• Eggs hatch into aquatic larva having
external gills and tail (similar to fish)
• Indirect development=
Metamorphosis
Tadpoles
Frogs
Herbivorous
Carnivorous
Aquatic
Aquatic & Terrestrial
Single loop circulation
Double loop circulation
Gills
Lungs
Parental Care FYI
• Overall, amphibians have a high fecundity and little or
no parental care. Parental care has been reported for
some species such as the gastric-brooding frog
(Rheobatrachus silus) from Australia. Female of the
gastric-brooding frog swallows the eggs after they are
fertilized and they develop in her stomach. When fully
developed into frogs, they are released through the
female’s mouth.
The Strawberry Poison-dart frog (Oophaga pumilio)
from Central America exhibits strong parental care as
well. Once the eggs are laid, the male ensures that they
are kept hydrated by transporting water. Then when
eggs finally hatch into tadpoles, the female transport
them on her back to suitable water-retaining location.
Surinam Toad
Darwin’s Frog
Environmental Interaction
• Require a somewhat cool environment
• Most amphibians hibernate during winter
months in soft mud of the bottoms of pools
and streams
• Some can tolerate freezing temperatures by
making a type of antifreeze by accumulating
glucose and glycerol in body fluids
• http://news.nationalgeographic.com/news/2
007/02/070220-frog-antifreeze.html
Environmental Interaction
• Are both predators and prey to others, for
protection amphibians have developed
– Poison glands
– Urinate
– Strong legs for leaping away
– Biting at predators
– Inflate lungs to avoid being swallowed
– Camouflage
Aposematic- warning
coloration
Toxic
Mimicry
Nontoxic
Yikes
• Worldwide, populations of frogs have
been decreasing and experiencing
mutations.
– Pollution, acid rain, ozone depletion,
pesticides/chemicals, introduction of exotic
predators, habitat destruction are a few
contributing factors
Click pic for vid on
Kihansi Spray Toad
• http://www.amphibianark.org/the-crisis/chytridfungus/ -Big problem for amphibians!
• http://news.nationalgeographic.com/news/2012/1
21217-chytrid-fungus-amphibian-frog-crayfishscience/
Golden Frog (Panama)
Click: Part 1
Click: Part 2
• Extinctions can be highly difficult to confirm due to the
need of long term intensive field surveys. Using the most
conservative approach to documenting extinctions, 34
amphibians are known to have vanished for ever since the
year 1500 as a result of human activities. The majority of
amphibian extinctions occurred during the last 100 years.
However, the real number of extinct species is very likely to
be an underestimate since amphibian inventories and
monitoring are lacking in most parts of the world. Most
scientists believe that more than 120 species are
suspected to be extinct since the 1980s. Many of those
“possibly extinct” amphibians have never been seen in the
wild for decades!
• http://news.nationalgeographic.com/news/2010/08/photo
galleries/100810-ten-lost-extinct-amphibians-frogs-
•Nearly one-third (32 %) of the world's amphibian species are known to be
threatened or extinct, 43 % are known to not be threatened, and 25 % have
insufficient data to determine their threat status.
•As many as 159 amphibian species may already be extinct. At least 38
amphibian species are known to be Extinct; one is Extinct in the Wild; while
at least another 120 species have not been found in recent years and are
possibly extinct.
•At least 42 % of all species are declining in population, indicating that the
number of threatened species can be expected to rise in the future. In contrast,
less than one percent of species show population increases.
•The largest numbers of threatened species occur in Latin American countries
such as Colombia (214), Mexico (211), and Ecuador (171). However, the
highest levels of threat are in the Caribbean, where more than 80 % of
amphibians are threatened or extinct in the Dominican Republic, Cuba, and
Jamaica, and a staggering 92 % in Haiti.
•Although habitat loss clearly poses the greatest threat to amphibians, a newly
recognized fungal disease is seriously affecting an increasing number of
species. Perhaps most disturbing, many species are declining for unknown
reasons, complicating efforts to design and implement effective conservation
strategies.
Map of threatened species
worldwide.
http://news.nationalgeographic.com/news/2011/08/pictures/110803-frogparasites-deformed-malformations-legs-animals-science/#/deformed-frogsparasites-amphibians-holding-frog-snail_38100_600x450.jpg