Transcript Lecture - Amphibians

Vertebrate Evolution
Chapter #1 – The Diversity, Classification, and Evolution of Vertebrates, pg. 2 – 15.
Chapter #2 – Vertebrates and Basic Structure, pg. 19 – 45.
Chapter #3 – Early Vertebrates, Jawless and Jawed Vertebrates, pg. 47 – 73.
Amphibians
What is a (Liss)Amphibian?
Liss = smooth (greek – referring to skin)
Amphibia = double life (greek – referring to metamorphosis)
Jurassic
Long hind limbs
(before break-up of Pangea)
HOP
Short, stiff bodies
Equal-sized limbs
Long, slender bodies
WADDLE
No limbs
Long, slender bodies
SLITHER
Figure 6.1 – Vertebrate Biology
Amphibians
Shared Derived Characteristics of Amphibians:
1) Smooth, Moist Skin:
• Absence of bony / keratinized scales (exception = caecilians)
• Absence of keratinized, true claws
• Mucous glands (prevent desiccation / slippery / disease-free)
Other Methods for Controlling Water Loss:
1) Behavioral Modifications:
Example:
Puerto Rican Coqui
Cool, wet nights
2) Pelvic Patch:
Highly vascularized skin;
absorbs majority of water
Warm, dry nights
3) Permeable Bladder:
Store dilute urine;
“Canteen” away from water
Amphibians
Shared Derived Characteristics of Amphibians:
1) Smooth, Moist Skin:
• Absence of bony / keratinized scales (exception = caecilians)
• Absence of keratinized, true claws
• Mucous glands (prevent desiccation / slippery / disease-free)
• Poison glands:
• Concentrated on
dorsal surface
Tarichatoxin
(newts)
Water-soluble alkaloid
(blocks Na+ channels)
• Produce diverse array
of chemicals
Epibatidine
(dart-poison frogs)
Lipid-soluble Alkaloid
(Blocks Ach receptors)
Non-addictive
painkiller
Batrachotoxin
(dart-poison frogs)
Lipid-soluble alkaloid
(Blocks closing of Na+ channels)
Sequestered via diet
Amphibians
Shared Derived Characteristics of Amphibians:
2) Multiple Methods of Respiration:
• Cutaneous – Gas exchange occurs across moist skin
• Buccopharyngeal – Gas exchange occurs in buccal cavity / pharynx
• Pulmonary – Gas exchange occurs in paired lungs (too small for all gas exchange)
• Gills – Larval forms and neotenics (neoteny = adults that retain juvenile characteristics)
3) Pedicellate Teeth:
• Crown and base of tooth separated by uncalcified dentine / fibrous tissue
• May allow for “flex” of tooth for prey handling (all carnivores)
4) Green Rods:
• Distinct type of retinal cell
• Hue discrimination in
dim light?
Teeth break easily – continuously replaced
Amphibians
Shared Derived Characteristics of Amphibians:
5) Unique Hearing Adaptations:
• Operculum – Columella Complex:
• Two bones in middle ear that transmit sound to inner ear (via oval window)
• Dual high / low frequency system
• High frequency (> 1000 Hz) = vibration of columella alone (air)
• Frogs (needs tympanum for amplification); Vocalization
• Low frequency (< 1000 Hz) = vibration of operculum-columella unit (ground)
• Vibration via leg bones / scapula (activated via opercularis muscle)
• Frogs & Salamanders; Predator / prey detection
• Inner Ear:
Basilar papillae:
Hair cell system – detects high
frequencies
Amphibian papillae:
Hair cell system – detects low
frequencies
Amphibians
Shared Derived Characteristics of Amphibians:
6) Levator bulbi muscle:
• Bulges eye outward; increases buccal cavity
Amphibians
Salamanders (10 families; ~ 515 species):
Diversity:
• First appearance in fossil record = Jurassic
Evolution associated w/ cool, wet forests
Order: Caudata (“Tailed Ones”)
* (~ 245 sp.)
• Primarily holarctic distribution:
North American = 9 of 10 families
(5 endemic)
• Neotropic = greatest # of species
All from single family
(Plethodontidae ~ 145 sp.)
Amphibians
Salamanders (10 families; ~ 515 species):
Morphology / Locomotion:
• Presence of tail (larvae / juveniles / adults)
• 4 equally-sized limbs (extend at right angle from body)
• Size range = 3 cm to >1 m
• Paedomorphosis widespread (aquatic life)
Chinese Giant Salamander
Respiration:
• Aquatic = primarily gills (some cutaneous)
• Cryptobrachidae = large skin folds
• Terrestrial = lungs (50%) / skin (50%)
Adults retain:
laterally compressed tail / flattened head
functional lateral line system
external gills (not always…)
• Anguilliform locomotion (walking-trot / swim)
Plethodontidae = lungless
skin (10%) & buccopharynx (90%)
Hypothesis:
Evolved in fast, cold water ( O2)
Lungs disadvantageous (buoyancy)
Amphibians
Salamanders (10 families; ~ 515 species):
Diet / Prey Capture:
• Generalist carnivores (primarily invertebrates)
• Aquatic = mouth gape
• Suction pulls prey into oral cavity
Cryptobrachus alleganiensis
movie
• Works will with gills / gill slits (one-way flow)
• Tongue = broad, flat, immobile
• Terrestrial = Thick, sticky tongue grabs prey
• Plethodontidae: Projective tongue
Why Plethodontids?
Buccal pump not necessary for breathing
Taricha torosa
movie
(no lungs)
Hyoid bone specialized for projecting
the tongue (elongated / lightened)
Hydromantes platycephalus
movie
http://autodax.net/feedingmovieindex.html
Amphibians
Salamanders (10 families; ~ 515 species):
Sensory Systems:
• Aquatic:
• “Taste” chemicals in water
• Vibrations – Retain lateral line system
• Terrestrial:
• Smell – Olfactory epithelium (volatile)
• Smell – Vomeronasal organ (Non-volatile)
• Sexually dimorphic (larger in males)
• Courtship / Identification (species / sex / individual)
• Highly advanced in Plethodontidae
• Nasolabial Grooves = Non-ciliated grooves; upper lip to nares
• Aids in collection / delivery of chemical cues (capillary action)
• Sexually dimorphic (esp. during reproductive season)
• Hearing – limited high frequency (no ear drum); primarily ground vibration
• Vision – acute; especially in plethodontidae
Amphibians
Sirenidae (sirens):
• Nocturnal
• Vocalization
Morphology:
• Eel-like; lack hind limbs (lack pelvic girdle)
• Paedomorphic; gills present
Habitat:
• Swamps / lakes / marshes (slow-moving water)
Reproduction:
• External fertilization; female nest guarding
Cryptobranchidae (Hellbenders):
Aquatic:
SE United States / NE Mexico
• largest individuals
• live 50+ years
Morphology:
• Dorsal-ventral compressed body (paedomorphic)
• Multiple folds in skin (cutaneous respiration)
Habitat:
• Clear, cold mountain streams / lakes
• Severely reduced ranges (loss of habitat)
Reproduction:
• External fertilization; Males = “den masters”
Aquatic:
Central China / Eastern United States
Amphibians
Amphiumidae (Amphiums):
• terrestrial egg-laying
• aestivate
Morphology:
• Eel-like; maintain four reduced limbs
• Paedomorphic; lack gills (lungs present)
Habitat:
• Sluggish streams / rivers; swamps
Reproduction:
• Internal fertilization; female nest guarding
Proteidae (Waterdogs):
Aquatic:
SE United States
• dissection specimen
• nocturnal
Morphology:
• Paedomorphic; feathery gills / caudal fins
Habitat:
• Lakes / streams
• Limestone caves (drastic reduction in numbers)
Reproduction:
• Internal fertilization; ♂ / ♀ nest guarding
Aquatic:
Eastern United States / SE Europe
Amphibians
Plethodontidae (example = Ensatina escholtzii):
Anatomy:
• Constriction at tail base = tail autotomy
• Very costly (tail = large fat reserve)
• ~ 10 – 12% tail regeneration (~ 2 years)
Habitat:
• Prefers cool forests with litter / dead trees
• Tolerates logging better than most plethodons
Terrestrial:
North / Central / South America & Europe
Reproduction:
• Mating begins (Nov.) and ends (March) with rains
• ♂ use hedonic glands / pheromones to attract ♀
• Methods of pheromone administration:
• Slap ♀ nares with hedonic gland (video)
• Innoculate ♀ with sharp teeth
• Elaborately patterned courtship “dance”
• “Tail straddle-walking” (unique to plethodons)
• ♂ repeats dance (~ 1 – 5 hours)
• Pathway / movement unique to each species
Pheromone:
Chemical cue that affects the
behavior and / or physiology
of a conspecific
Amphibians
Plethodontidae (example = Ensatina escholtzii):
Reproduction:
• ♂ lays down spermatophore; ♀ picks it up (video)
• ♀ lay 8 – 12 eggs (~ 5 mm)
• Terrestrial – in logs; under logs; in burrows
Terrestrial:
North / Central / South America & Europe
Sperm Cap
• ♀ guards eggs ( predation / fungal infection)
• Direct development of eggs (~60 – 120 days)
Growth / Maturation:
• Sexual Maturation ~ 4 years
• Life Span ~ 10 years (best guess)
Gelatinous Base
Amphibians
Rhyacotritonidae: (example = Rhyacotriton olympicus)
Anatomy:
• Full metamorphosis
• No operculum / opercular muscle ( hearing)
• Highly reduced lungs (cutaneous respiration)
Habitat:
• Cold, clear streams / seepages / waterfalls
• Very desiccation intolerant
• Low heat tolerance (susceptible to logging)
Reproduction:
• Internal fertilization
• Spermatophore deposition
• Tail-wagging display
• Aquatic egg-laying
• No nest guarding
Growth / Maturation:
• Sexual Maturation ~ 4 years
• Life Span ~ 10 years (best guess)
Anti-predator Display
Terrestrial:
NW United States
Amphibians
Larval Anatomical Specializations:
Pond Larvae
Ambystomatidae
Salamandridae
• High body profile
• broad tail fin extending up to head
• long, plume-like gills
• Only front legs at hatching
Stream Larvae
Dicamptodontidae
Rhyacotritonidae
Plethodontidae
• Depressed body profile
• Narrow tail fin (not onto trunk)
• Short, thread-like / curly gills
• All four legs at hatching
Amphibians
Salamandridae (example = Taricha granulosa):
Habitat:
• Prefer older growth forests during “newt” phase
Warning Coloration:
• Flashes tail & brightly colored stomach
Terrestrial:
Chemical Defense:
• Tarichatoxin (non-protein – VERY poisonous)
• Neurotoxin – blocks NA+ channels (paralysis)
• Small dose lethal to birds / mammals
• Large dose lethal to humans
Red-spotted Garter Snake
“The Arms Race”
North America / Europe / NW Africa / Asia
Assignment:
http://evolution.berkeley.edu/evolibrary/article/biowarfare_01
Questions Posted on Class Website…
Amphibians
Salamandridae (example = Taricha granulosa):
Reproduction:
• Adults migrate to ponds / lakes (1 – 3 weeks prior)
• Breeding from April – July (annual / biannual)
• ♂ release pheromone (hedonic gland)
• Amplex with ♀ (ward against rivals)
• ♀ signals willingness to mate by raising head
• ♂ lays down spermatophore
• ♀ lay 200 – 375 eggs
• Incubation ~ 20 – 35 days
Growth / Maturation:
• Metamorphosis ~ 4 – 5 months
• Sexual Maturation ~ 4 – 5 years
• Life Span ~ 20 – 25 years
Terrestrial:
North America / Europe / NW Africa / Asia
Amphibians
Dicamptodontidae: (example = Dicamptodon tenebronsus)
Anatomy:
• Full metamorphosis / facultative paedomorphosis
• Large (up to 30 cm SVL)
• Well-developed lungs / blade-like teeth
Habitat:
• Damp coniferous forests (near streams / seeps)
• Paedomorphic = moving water
• Diet: Opportunistic feeders (sit-and-wait)
Reproduction:
• Internal fertilization
• Breeding occurs in water
Will eat small mammals
• Eggs (~ 200) deposited singly
wood / rocks in water (female nest-guarding)
Growth / Maturation:
• Metamorphosis ~ 2 years
• Sexual Maturation ~ 2 years
• Life Span = long-lived…
Terrestrial:
NW United States / SW Canada
Amphibians
Ambystomatidae: (example = Ambystoma macrodactylum
Anatomy:
• Full metamorphosis / paedomorphosis (rare)
• Stout-bodied; thick-tailed
Habitat:
• Wide range of habitats (grasslands  forests)
• Subterranean (“mole” salamanders)
• Close to water (~ within 100 m)
Terrestrial:
Western North America
• Enter torpor during winter (below frost line)
Reproduction:
• Earliest amphibian breeders (Pacific Northwest)
• Migrate to breeding ponds (fidelity - ♂ arrive first)
• Eggs (~ 100 – 400) deposited in clusters
Growth / Maturation:
• Metamorphosis ~ 2 years
• Sexual Maturation ~ 3 – 5 years
• Life Span ~ 10 years
Cannibalistic
larvae
Amphibians
Caecilians (6 families; 180 species):
• Long, slender body; small dermal scales
• Legless; no post-anal tail
• Most species blind as adults
• Specialized sensory tentacles (snout)
• Diet = small insects / earthworms
Life History:
• Very little known about courtship
• Internal fertilization (via intromittent organ)
• 75% viviparous (live young - matrotrophic)
• Initial nutrition = yolk
• Subsequent nutrition = “uterine milk”
• Breath via fetal gills
• Young caecilians 30 – 60% adult BL!
• 25% oviparous (lay eggs – may brood eggs)
Order: Gymnophiona (“Naked snake”)
Tropics (S. America / Africa / S.E. Asia)
Fossorial / Aquatic
Amphibians
Frogs (29 families; ~ 4800 species):
Diversity:
First appearance in
fossil record = Jurassic
Order: Anura (“Without Tail”)
* (~ 1100 sp.)
• Ubiquitous (except Antarctica):
North American = 10 or 29 families
• Neotropic = greatest # of species
Most Diverse Family
Leptodactylidae ~ 1100 sp.
Amphibians
Frogs (29 families; ~ 4800 species):
Morphology:
• Body specialized for jumping:
• Hind legs elongated; tibia / fibula fused
• Large pelvis; short vertebral column
• Urostyle (Fused posterior vertebra)
• Size variable (1/2”  1 ‘)
Toe Pads:
Viscous mucus = “sticky”
Locomotion:
Jumping Frogs
Long hind limbs
Hopping Frogs
Short limbs / Robust body
Semi-aquatic Frogs
Webbed feet / stream-lined
Arboreal Frog
Slim waist / long legs
Amphibians
Pacific Tree Frog
Frogs (29 families; ~ 4800 species):
Bullfrog
Spadefoot Toad
Vocalization:
• Associated with reproduction (advertisement calls)
• Identify species / sex of caller
• Can function in mate choice (e.g., male size)
• Vocalization is a tradeoff:
• Costs:
1) Vocalization energetically expensive
2) Vocalization announces location
• Benefits:
Tungara Frogs:
“Whine – cluck”
Females prefer / bats prefer
“Whine”
Females / bats less preference
“Whine – cluck” only observed
when large choruses present
Amphibians
Frogs (29 families; ~ 4800 species):
Reproduction:
• Mating systems:
1) Explosive Breeders (season
= few days)
• Temporary aquatic habitats
• Large aggregations; limited mate choice
2) Prolonged Breeders (season = months)
• Males defend territories
• Males out-number females; strong mate choice
• Fertilization primarily external
• Amplexus: Embrace of male and female frog
• Brings cloacae in close proximity (fertilization)
Inguinal Amplexus
• May last hours to several days
Fertilization can
occur internally…
Axillary Amplexus
Amphibians
Frogs (29 families; ~ 4800 species):
Reproduction:
• Egg Development:
Directly in water
Direct Development
(egg protection)
(tadpole protection)
Guard Eggs
Vegetation over water
Foam Nest
(egg protection)
(egg protection)
Bromeliad Nest
(egg protection)
(tadpole protection)
• Parental Care (common):
Carry Eggs
(Mid-wife Toad  ♂)
Carry Eggs / tadpoles
(Sirinam Toad  ♀)
Internal Brooding
(♀  Gastric Brooders)
Viviparous
(Morogoro Tree Toad)
Amphibians
Still Water:
Ovoid bodies
Tails with large fins
Frogs (29 families; ~ 4800 species):
Tadpoles:
• Aquatic larval stage of frogs
• Advantages:
1) Exploit non-adult resources
• Tadpoles = aquatic / herbivores
• Adults = terrestrial / carnivores
2) Efficient eating machines (rapid growth)
Fast Water:
Stream-lined bodies
Small tail fins
Metamorphosis: (3 stages)
• Triggered by thyroid hormone
Premetamorphosis
Prometamorphosis
Metamorphic Climax
• Increase in size
• Little change in form
• Hind legs appear
• Rapid decline in growth
• Fore legs appear
• Tail regresses
• Mouth broadens; long  short gut; degeneration of gills; dermal gland formation
Amphibians
Rhinophrynidae: (Burrowing Toad)
• Single species
• Unique tongue
Morphology:
• Short, powerful limbs; tubercle present
• Robust body; pointed head (cornified tip)
Habitat:
• Sub-humid areas; surface after heavy rains
Fossorial
Reproduction:
• Explosive breeder; aquatic tadpole
North America / Central America
Leptodactylidae (Neotropical frogs):
• Among largest
Morphology:
• Highly variable (10 mm 
• Many nocturnal
250 mm)
Habitat:
• Variable:
• Leaf litter layer
• Fully aquatic
• Arid regions
• High plateaus
Reproduction:
• External / internal fertilization
• Aquatic tadpoles / direct development
Terrestrial
North / Central / South America
Amphibians
Microhylidae: (Microhylid frogs)
Morphology:
• Highly variable (10 mm 
• Commensal assoc.
with spiders
100 mm)
Habitat:
• Variable (Arid deserts  Wet rain forests)
Reproduction:
• Explosive breeders / prolonged breeders
• Aquatic tadpoles / direct development
Terrestrial / Fossorial / Arboreal
Ubiquitous
Dendrobatidae (Poison-dart frogs):
Morphology:
• Relatively small; highly aposematic
Habitat:
• Tropical rainforests
Reproduction:
• Most lack amplexus
• Small clutches; parental care
• Poisonous
• Introduced to
Hawaii
Terrestrial
Central / South America
Amphibians
Pipidae: (clawed frogs)
• Tongueless
• Model lab organism
Morphology:
• Dorso-ventrally compressed body
• Limbs splayed laterally; large, webbed feet
Habitat:
• Almost every type of body of water
Reproduction:
• Aquatic tadpoles / direct development
Aquatic
South America / Africa
Cane Toad (Bufo marinus)
“… one of the 100 worst invasive
Invasive Species
species worldwide.”
Specialist Group
1) Prolific breeders (~ 33,000 eggs)
2) Tolerance for temperature / salinity
3) All stages of life poisonous (bufotoxin)
4) Generalist diet (including cat food)
• Trap / hand catch frogs
• Biocontrol (virus)
No native toad species
1935
~ 100 Marine toad
released…
Amphibians
Ascaphidae (example = Ascaphus truei):
Anatomy:
• Males have tail-like intromittent organ
• Highly vascularized cloacal extension
• Tympana absent; do not call
Habitat:
• Swift mountain streams with cobbled substrate
• Primarily aquatic; terrestrial after heavy rains
Reproduction:
• Internal fertilization (only frog species…)
• Inguinal amplexus; ♂ “tail inserted into ♀ cloaca
• Small clutches of large eggs (place under rocks)
• Tadpoles have suction disks / reduced fins
Growth / Maturation:
• Metamorphosis ~ 2 – 3 years
• Sexual Maturation ~ 8 – 9 years
• Life Span ~ 12 – 20 years
Aquatic:
Northwest United States
Amphibians
Pelobatidae (example = Scaphiopus intermontana):
Anatomy:
• Keratinous, spade-like metatarsal tubercle
• Rotund body; short legs; large eyes
• Glandular, tuberculate skin
Habitat:
• Found in sagebrush country (shallow burrows)
• Over-winter in self-made burrows (~ 1 m deep)
• Survive osmotic stress via urea in body fluids
Reproduction:
• Explosive breeding; permanent / ephemeral waters
• 300 – 500 eggs / female; hatch = 2 – 4 days
Growth / Maturation:
• Metamorphosis ~ 1 month
• Sexual Maturation ~ 1 – 2 years
• Life Span ~ 10 – 13 years
Terrestrial:
North America / Europe / Asia / Africa
Amphibians
Bufonidae (example = Bufo boreas):
Anatomy:
• Bidder’s Organ: Rudimentary ovary (on male testis)
• Rotund body; dull coloration
• Prominent skin glands (toxic - peptides)
Habitat:
• Various elevations; Close water contact
• Over-winter in existing burrows near / in water
Reproduction:
• Prolonged breeders; ♂♂ actively search out ♀♀
• Males lack call; “chirp” = release call
• ~ 6000 eggs / clutch; laid in double row strings
Growth / Maturation:
• Metamorphosis ~ 1 – 2 months
• Sexual Maturation ~ 4 – 6 years
• Life Span ~ 10 – 15 years
Terrestrial:
Cosmopolitan
Amphibians
Hylidae (example = Hyla regilla):
Indicator
Species
Anatomy:
• Relatively small: 1 – 2 inches in length
• Toe discs present
• Polymorphic colors; change with temp / humidity
Habitat:
• Low shrubbery during wet season
• Over-winter in moist, cool retreats during winter
Reproduction:
• Migration to breeding ponds triggered by warm, winter rains
• ♂♂ enter pond, begin calling (attract ♀♀; warn ♂♂)
• ~ 500 - 750 eggs / clutch; ~ 3 clutches / season
Growth / Maturation:
• Metamorphosis ~ 2 months
• Sexual Maturation ~ 1 – 2 years
• Life Span ~ ???
Primarily Arboreal:
North / Central / South America
Amphibians
Ranidae (example = Rana Aurora ):
Red located on lower
abdomen / hind limbs
Anatomy:
• Mid-sized body: 2 - 3 inches in length
• Long rear legs; exceptional leaping ability
• Presence of vocal sacs dependent on sub-species
Habitat:
• Require riparian vegetation near ponds / streams
• Move into upland forest outside of breeding season
Terrestrial:
Cosmopolitan
Reproduction:
• Reproduction occurs November – April (assures cold water)
• Extensive migrations to breeding sites not uncommon
• ~ 200 - 1000 eggs / clutch; attached to aquatic vegetation
Growth / Maturation:
• Metamorphosis ~ 3 – 4 months
• Sexual Maturation ~ 2 – 3 years
• Life Span ~ 10 years
Believed to be inspiration for Twain’s
"The Notorious Jumping Frog
of Calveras Country"
Amphibians
Amphibian Decline:
• Nearly 1/3 of amphibian species
are threatened (~ 2000 species)
• ~ 150 species believed extinct over
the past several years
• 43% of all species declining in
population (< 1% show increases)
• Regions:
• Latin America (largest #)
• Caribbean (largest %)
• Madagascar
Global Distribution of Amphibians
• Eastern Australia
• Central / Southern China
• West Africa
Why are populations
declining?
(7 major hypotheses…)
Global Distribution of Threatened Amphibians
Amphibians
Amphibian Decline - Reasons:
1) Habitat Changes:
California redlegged frog
Habitat Destruction:
Complete elimination of ecosystem
leading to total loss of biological function
Habitat Fragmentation:
Populations isolated due to
removal of linking habitat
Habitat Alteration:
Changes to ecosystem that
adversely affect function
Amphibians
Amphibian Decline - Reasons:
1) Habitat Changes:
California redlegged frog
Habitat Destruction:
Complete elimination of ecosystem
leading to total loss of biological function
Habitat Fragmentation:
Populations isolated due to
removal of linking habitat
Habitat Alteration:
Changes to ecosystem that
adversely affect function
2) Introduced Species:
Sunfish vs. Red-legged Frog / Pacific Tree Frog
Bullfrog vs. Anything that moves
Amphibians
Amphibian Decline - Reasons:
3) Overexploitation:
• Education (e.g., dissection)
• Research
• Bait
Red-legged Frog:
Prized for legs
Illicit Pet Trade
(~ 80,000 harvested / year)
(Goliath Frog ~ $3000)
4) Climate Change:
Wood Frog – New York
Great-crested Newt
Breeding earlier than usual…
Drought
Amphibians
Amphibian Decline - Reasons:
5) UV Radiation:
6) Chemical Contamination:
Atrazine (herbicide):
Disrupts steroidogenesis resulting in
demasculanization and hermaphroditism
Acidification:
Reduced hatching success
Pacific Tree Frog:
Developmental and physiological
abnormalities and reduces larval
survival
Nitrogen Pollution:
Reduced feeding activity, swim less vigorously,
Display disequilibrium, development malformations
7) Disease:
Common Frog
Virus
Yellow-legged Frog
Bacteria
Western Toad
Water Mold
Pacific Tree Frog
Trematodes
Amphibians
Amphibian Decline - Reasons:
5) UV Radiation:
6) Chemical Contamination:
Atrazine (herbicide):
Disrupts steroidogenesis resulting in
demasculanization and hermaphroditism
Acidification:
Reduced hatching success
Pacific Tree Frog:
Developmental and physiological
abnormalities and reduces larval
survival
Nitrogen Pollution:
Reduced feeding activity, swim less vigorously,
Display disequilibrium, development malformations
Synergisms most likely at work…
7) Disease:
Common Frog
Virus
Yellow-legged Frog
Bacteria
Western Toad
Water Mold
Pacific Tree Frog
Trematodes