Amphibian diversity Flashcards
Which Superclass do the Amphibia exist within?
The Tetrapods
Who are the Lissamphibia
Extant amphibia
Describe the Lissamphibia
- permeable skin
- extensive vascularisation
- smooth mucus-covered thin skin with dermal glands (for active water and active salt uptake)
- wide diversity of body forms
- diverse reproductive strategies
- carnivorous feeding
- habitats from deserts to caves to trees to ponds
- NEVER back in the sea.
Give the 3 Orders of Lissamphibia
- Urodela (salamanders)
- Anura (frogs and toads)
- Caecilians
Describe the tadpole
- aquatic early developmental stage
- ancestral
Describe the life of a tadpole
- eggs fertilised by attending male as they are being laid in the water
- tadpole feeds first on algae; later on insects
- grows and develops gills
- in the later tadpole, the hind legs grow and lungs develop,
forelegs appear and the tail regresses - froglet becomes terrestrial
- grow on land
- return to water to breed several years later
Describe Lissamphibian slimy skin
- epidermis soft with local horny regions
- dermis contains numerous glands opening to the surface
- chromatophores expand to change skin colour
- mucous glands secrete mucus to cover the skin
- poison glands release alkaloids under active control
- fibrous connective tissue overlaying muscle
Describe a frog’s horny regions
- keratinous
- protective
- moulted
Describe Lissamphibian skin secretions
- batrachotoxin
- bufotoxin
- Epipedobates produces a potent painkiller
batrachotoxin
- deadly alkaloid
- 0.2 mg is fatal to humans
- Phyllobates terribilis
bufotoxin
- noxious irritant
- produced by toads
Epipedobates
Central-American frog
Describe the epidermal chromatophores
- used in camouflage: Peron’s tree frog (Litoria peronii)
- used in aposematism (Dendrobates azureus)
Describe Amphibian gas exchange
- lungs
- many aquatic salamanders have external gills too
- plethodontid salamanders have neither lungs nor gills
Describe Amphibian lungs
- relatively small
- simple sacs or with a few septa to increase the blood to air exchange area
- large alveoli
- slow diffusion
- OK with low BMR
Describe Amphibian inspiration
- hyoid lowered, filling buccal cavity
- air into open nostrils
- nostrils close and glottis opens
- hyoid raises
- air forced into lungs
Describe Lissamphibian expiration
- nostrils and glottis open
- trunk muscles contract, emptying the lungs
- hyoid fluttering purges lungs before re-filling
Describe Lissamphibian cutaneous exchange
- skin is richly vascularised
- exchange through the lungs
and the skin of a toad in air depends on temperature
What happens to Lissamphibian gas exchange at low temperatures?
- more exchange occurs via skin than via the lungs.
- in winter, a toad relies almost completely
on cutaneous exchange.
What happens to Lissamphibian gas exchange at high temperatures?
- lungs become more important for O2
- skin becomes more important for CO2 exchange
Describe the amphibian heart
- dual system
- three-chambered
Label an amphibian heart
- left carotid arch
- left systemic arch
- left pulmocutaneous arch
- systemic veins
- left pulmonary vein
- right atrium
- aorta
- left atrium
- interatrial septum
- atrioventricular valve
- ventricle
- right atrium
- spiral valve
- opening of left pulmocutaneous arch
- right pulmocutaneous arch
- right systemic arch
- right carotid arch
- right pulmonary vein
Air and water have different refractive indices
1.0 v. 1.33
Describe Lissamphibian vision
- must be able to accommodate air and water
- lens is rigid and of high refractive index (more spherical in aquatic amphibians)
- lens muscle pulls the lens forwards to accommodate nearer objects
- distance perception relies on the angle of convergence of the two eyes: binocular overlap in fields of the two eyes
- foveal region
- retina has purple and green rods
- nictitating membrane ‘blinks’ to keep the cornea moist
Describe green rods
- unique to amphibians
- more sensitive to movement
Describe Urodela - the basics
- newts and salamanders
- 515spp
- Eurasia and North America to Central America (neither Africa nor Australia)
- e.g. Neurergus kaiseri
Describe Anura - the basics
- frogs and toads
- 4800+ spp
- all continents except Antarctica
- e.g. Tree frog
Describe Caecilia - the basics
- otherwise known as “caecilians”
- 180+ spp.
- tropics around the world
- e.g. Ichthyophis glutinosis
Describe Urodela - the specifics
- long tails
- least derived of the lissamphibians
- confined to the northern hemisphere
- greatest diversity is in the southern U.S. and tropical N. America
- range in adult body size from c.50 mm long to over 1.5 m long
Give an example of a 50mm Urodel
some plethodontid salamanders
Give an example of 1.5m long Urodel
Japanese giant salamander
Describe the typical Urodel lifestyle
only aquatic in breeding season
Describe Ambystoma
- can breed either as the adult salamander form, or in gill-bearing, permanently-aquatic “larval” axolotl form
Describe Megalobatrachus or Andrius
- live in cold mountain streams of China and Japan
- grow to 1.5m length
Describe Cryptobranchus
- large US relative
- highly folded large area skins
Describe Amphiuma
- vestigial legs
- aquatic
- lives in muddy swamps
Describe Siren
- lost its hind legs
- retains larval gills
- acquatic
Describe Proteus and Typhlomolge
- live in caves
- permanently aquatic with external gills
- colourless
Describe Urodele skeletons
- bones of the skull are weak and reduced,
with large open orbits - ribs are short, extend beyond the trunk and do not form a rib-cage
- long tail used in both swimming and walking
- both pairs of legs are short and weak: the wrist and ankle are weakly ossified: four fingers and five toes
- only a single weak sacral vertebra
Describe Urodele swimming
- tall long tail fin undulates but lacks fin rays
- fin is reduced or absent in terrestrial phases
- short legs minor contribution
- myotomes in both trunk and tail cause lateral body undulation
Descrive Urodele walking
- bending of body increases effective arc of leg swing
- bending at wrist and elbow as well as ankle and knee
- body bent to side of leg overlap
- body straightens in mid stride
- body bent to opposite side
- body rises and falls
Describe the position of a Urodel’s hands and feet
feet first
As a newt tries to run faster, the body
- sags
- is dragged along the substrate
Describe the Urodel sprawling gait
- associated with complex leg movements
- up-down and side-to-side body undulation
Describe the mechanics of Urodel walking
- femur swings approx. in horizontal plane
- rotation of tibia on fibula
Describe Urodel courtship
- elaborately patterned male dorsal fin and tail enlarge
- become coloured in the breeding season
- mating usually occurs in water
- male may hold the
female, transferring pheromones - visual displays
Describe Urodel fertilisation
- bag of sperm joined to gelatinous basal attachment
- occurs in the oviduct
- zygotes/embryos may be retained.
Describe Urodel development
- eggs often deposited singly on vegetation
- develop as tadpoles with external gills
Describe European newts
front legs are the first to grow.
Describe the Mexican axolotl
- neotenous salamander that retains its larval gills
- lives and breeds in water
- similar to Siren and Necturus
Describe Order Anura
- lack tails
- specialised for walking and jumping
- greatest diversity in the wet tropics
- found in deserts and tundra
- range in adult body size from c. 10 mm to over 30 cm long and over 3 kg weight
Give the 3kg frog
Goliath frog; Conraua goliath
Describe Triadobatrachus
- 5 toes on front feet
- 14 presacral vertebrae
- short ilium
- no urostyle
- short hind limbs and toes
Describe modern Bufo
- 4 toes on front feet
- 5 to 9 presacral vertebrae
- elongated ilium
- urostyle
- long hind limbs and toes
What are the well-known toad and frog genera of Europe?
Bufo and Rana
Describe Anuran diversity
- Hyla: large genus of tree frogs. - Pipa and Xenopus: totally
aquatic tropical toads that lack tongues. - Pipa, Alytes and Gastrotheca: interesting parental care strategies
- Breviceps: desert frog specialised for burrowing.
- Ascaphus, the “tailed frog”: internal fertilisation and an extended urostyle
Canadian wood frog (Rana sylvatica)
frogsicles!
Describe anuran skeletons
- spine very short
- hind legs long
- no tail
- flimsy skull, large orbits
- shock-absorbent shoulders, arms and hands
- long ilium, femur, tibio-fibula and foot
Describe anuran jumping
- after take-off, hind legs are fully extended
- many small frog spp. can clear over 1.5 m
- 10m triple jump
Describe the skeletal movement during frog jumping
leg extension occurs at four hinges:
- sacro-iliac joint
- ilio-femoral joint
- femoro-tibial joint
- tibio-tarsal joint
Describe Anuran landing
- front legs fully extended
- kinetic energy absorbed by bending arms, and separation of the flexible ventral parts of the pectoral girdle
- hind legs re-flexed after landing
Describe Anuran tree climbing
- curling digits
- adhesive toe-pads
- e.g. Hylidae
Describe Anuran acoustic communication
- ear drums
- lungs grossly dilated
- vocal sac collapsed
- air forced from lungs
- vocal sac inflates
Describe the Anuran ear drum
- connected by the columella to the inner ear
- hear from c. 50 Hz to 8 kHz
- can locate sources to ±10 degrees
columella
or stapes
Urodels are
mute and deaf
Inflating the vocal sac via the larynx produces sound as
single pulses
or a train of pulses.
Describe the skin of the vocal sac
- elastic
- lungs are re-filled as it collapses
- silent phase
Describe Anuran songs
- species specific
- used in mate-attraction, territorial marking, aggression and as alarm signals
Describe Alytes, the midwife toad
produces long pure-tone pulses at about 1.3 kHz
to call females to his territory
Describe Dendrobates
poison-arrow frog
Describe Anuran fertilisation
- external
Describe Anuran constraints
- cannot lay large egg-batches
- produce a few relatively large eggs that develop directly in the damp leaf litter
Describe Anuran size
- froglets and toadlets of most European species are only 10-15mm long
- vulnerable to desiccation.
- many tropical species only 10-15mm long when adult;
can only survive in rain forests, tend to live on or within the wet undergrowth (where they hide during the heat of the day)
Describe the “conventional” frog/toad strategy
- many eggs, pond-dwelling tadpole that feeds on pond-life and grows to a size at which it can safely become a froglet
- only valid where there is a rich, comparatively safe seasonal niche
Describe Anuran post- oviposition parental care
- buccal and gastric brooders swallow newly-laid eggs which develop into froglets.
Describe the Gastrotheca male
- eggs in dorsal pouch
- pouch opening
Describe Pipa pipa
- large fully-aquatic Surinam toad
- females carry eggs in pouches that form in the dorsal skin where they develop into froglets.
Describe Rhinoderma darwinii male
incubates the eggs in his vocal sac where they develop into froglets
Describe Rheobatrachus
- Australian gastric-brooding frog
- female incubates eggs in stomach
Describe Anuran successes
- nearly 5,000 spp.
- adept at gaining water and tolerating water loss
- parental-care mechanisms that emancipate them from the conventional egg-tadpole-frog life cycle
- within the tropics, they include the smallest tetrapods
- can hop, swim and climb, thereby widening their range of habitats and ecological horizons
- low BMR and being water-tolerant enables them to exploit impoverished niches that cannot support others
- many are too toxic to eat
- cryptic and agile
How many species of tree frog are there?
700+
How many species of poisonous Anuran are there?
- 450 spp of toads
- 200+ spp. of poison arrow frogs
How many species of land and swamp frogs are there?
700+
Why are Anuran in decline?
- human-influenced climate and habitat change such as intensive farming and de-forestation
- spread of fungal infections
- increasing use of herbicides & fertilisers.
Describe the Order Caecilia
- alternative name: Apoda
- lack legs
- specialised burrowers
- inhabit soil & water in the wet tropics excluding Australia.
- range in adult body size from c. 100 mm to over 0.5 m long
- only 160 spp.
Describe the morphology of the Order Caecilia
- small weak eyes covered with skin
- long cylindrical trunk
- long right lung
- very short post-anal tail
- no ears
- retractible chemo-sensory tentacles
- skin thrown into rings; rings of small scales used to grip the
walls of a burrow - ## smooth rounded head for pushing through soil
Describe Ichthyophis
- southern Asia
- Caecilian
- burrows in damp soil
Describe the Caecilia skull
- large nasal openings
- tentacle cavity
- many sharp pedicellate teeth
- small orbits and eyes
- robust and heavily ossified
- strong lower jaw
- atlas
- rib
- V2
Describe Dermophis
- central American
- Caecilian
- burrows in damp soil
Describe Caecilian concertina burrowing
- concertina forms an anchor, from which the front of the body can be pushed forwards
- part of the trunk is made rigid by muscles acting on helical fibres in the skin
- new concertina forms an anterior anchor, allowing rear of the body to be pulled forwards
- robust spear-shaped head acts as a ram
- part of the trunk is drawn-up passively into the anterior concertina
Describe Caecilian reproduction
- fertilisation is internal via a male intromittent organ inflated from the cloaca
- development is essentially direct without a metamorphosis
Characteristic feature of Lissamphibia
slimy skin
Describe archaism in Caecilia
- full set of teeth,
- complete rib cage
- no sternum
- scales
- a strong skull
Describe the parallels between Caecilia and snakes/legless lizards
- loss of all limbs and girdles
- spade-like penetrating skull
- long rib-bearing trunk
- short tail
- concertina locomotion
- a single long (R) lung;
- loss of ears
- vestigial eyes with permanent covers, used mainly as light detectors
- other unique sense organs
- internal fertilisation -> viviparity in some
