Kingdom – AnimaliaPhylum - ChordataClass Amphibia3 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

• 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/index.htm

• Salamanders • Newts (Efts)• Mudpuppies• Sirens

Click

Axolotl

adapted from http://gideon.k12.mo.us/teachers/jswilley/htdocs/Classification%20of%20Animals.ppt

Spanish Ribbed Newt

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.htm

Horror Frog

adapted from http://gideon.k12.mo.us/teachers/jswilley/htdocs/Classification%20of%20Animals.ppt

Body Plan• 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

• 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

Click:Rain Frog

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

• 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

Click!

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• MEDULLA OBLONGATA- controls autonomic body

organs, relays info from body • CEREBELLUM-muscle coordination & balance• OPTIC LOBES- process info from eyes and other senses• CEREBRUM- higher thinking, learning, memory,

reasoning, integrates behavior• 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

http://libarynth.org/_detail/imagescleaned_washed_fiji_tree_frog_eggs_close-up.jpg?id=when_nature_inflates

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.

Darwin’s Frog

Surinam Toad

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/2007/02/070220-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

Mimicry

Toxic

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/chytrid-fungus/ -Big problem for amphibians!

• http://news.nationalgeographic.com/news/2012/121217-chytrid-fungus-amphibian-frog-crayfish-science/

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/photogalleries/100810-ten-lost-extinct-amphibians-frogs-science-environment-pictures/

•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-frog-parasites-deformed-malformations-legs-animals-science/#/deformed-frogs-parasites-amphibians-holding-frog-snail_38100_600x450.jpg