Topic 6: Amphibian Diversity What are Amphibians? What are

Topic 6: Amphibian Diversity
What are amphibians?
What are the three major amphibian clades?
What are some trends in amphibian
evolution?
* Introduction to the biology of each clade:
Gymnophiona
Urodela
Anura
What are Amphibians?
The Amphibia
is a diverse
clade, with
many
__________
groups
Extant (crown)
amphibians
make up the
____________
Benton 1997, Fig 4.21
What are Amphibians?
Synapomorphies
What are Amphibians?
Pedicellate, bicuspid teeth
Ear with stapes and operculum
Synapomorphies
Skin with _________ and ________
glands
Green rod receptor cells in eyes
Lost in Gymnophiona
Short, straight ________ that do not
encircle the body
Reduction of skull bones via
__________________
Metamorphosis is unique among
tetrapods but plesiomorphic
Pough et al 2004, Fig 2-6
Pough et al 2004, Fig 2-5
Paedomorphosis
Paedo ~ child (Gr), morph ~ form (Gr)
A type of heterochrony, which is a _______________
_______________________
The retention of juvenile (child-like) characteristics
into adulthood/sexual maturity
Non-herp example:
Paedomorphosis
Paedomorphosis is
prevalent in the _______
Retention of gills in adult
axolotl
Missing late-developing
bones
Large orbits – form early
during development
Relative hairlessness and upright face of humans
1
What are the three major amphibian clades?
What are the three major amphibian clades?
Lissamphibia
Many synapomorphies
~5,300 extant species
Three Major clades
More than Mammalia
______________: 167 spp
______________: 516 spp
___________: ~4,800 spp
Photos: KP Bergmann, Pough et al. Fig 3-8
Photos: KP Bergmann, Pough et al. Fig 3-8
Gymnophiona
Major Trends in Lissamphibian Evolution
Gymnophiona are caecilians
Body ____________
and limb reduction
Highly derived
Strange morphology
Elongate and limbless
Gymnophiona
Urodela
Microsaur
Body ____________
and stiffening
Anura
Pough et al 2004, Fig 3-8
Gymnophiona – General Features
Elongate bodies
____________, terrestrial, or aquatic
Aquatic habits are derived
Many structures are reduced
Gymnophiona - Synapomorphies
Annulated bodies
Annulus – Ring L.
Homologous with ______________ in Urodela
Male Typhlonectes
(cloaca)
___________
Limbs
__________ reduced or absent
Typhlonectes
Pough et al 2004, Fig 3-8
2
Gymnophiona - Synapomorphies
Gymnophiona - Synapomorphies
_______________ reduced or absent
Associated with body elongation
This is the same side lung as is reduced in snakes
Gymnophiona includes the largest lungless tetrapod (Typhlonectes)
_________________
Involved in chemoreception
Contains glands, ducts, and muscles
Located between eyes and nostrils
Protrusible from the skull
nostril
Why would caecilians be less reliant on their lungs than snakes?
Its position is phylogenetically informative
Tentacle
foramen orbit
Pough et al 2004, Fig 3-9
Gymnophiona - Synapomorphies
_________________
Gymnophiona - Reproduction
A projection of skin from the cloaca in males
Used as an intromittent organ
_______________ fertilization
Internal fertilization
Male Typhlonectes
(cloaca)
What is the intromittent organ called?
~70% oviparous, rest are viviparous
______________ species
Eggs can be aquatic or terrestrial
When terrestrial, there is parental care
______________ species
Young are nourished by secretions from oviduct
After birth, mother’s skin produces edible secretions
Typhlonectes
(mating)
Gymnophiona – Scales?
Deep scales in dermis
Only in some species – not a synapomorphy
Only amphibians with scales
surrounded by poison and mucous glands
Pough et al 2004, Fig 3-10
3
Gymnophiona - Synapomorphies
Fusion of bones in skull
Skulls are highly ossified and bones are closely associated
Very solid, akinetic structure
Fusion into os basale and maxilopalatine
Pough et al 2004, Fig 3-9
Gymnophiona - Synapomorphies
Three types of amphibian skulls
______________
______________
______________
• Temporal region
open
• Skull is
intermediate
• Skull is
completely roofed
• Anura & Urodela
• Gymniophiona
• Gymnophiona
Pough et al 2004, Fig 2-6, 3-9
1
Gymnophiona - Fossoriality
Caecilians have many adaptations to a fossorial existence
Non-fossorial forms are derived
What are some of these adaptations?
http://digimorph.org/specimens/Dermophis_mexicanus/
Adaptations for fossoriality
______________________
______________________
______________________
______________________
______________________
______________________ is a result of a
fossorial existence
2
Gymnophiona - Distribution
Gymnophiona – Diversity & Phylogeny
6 major clades
Don’t worry about
their names
33 genera, 167 spp.
109 spp. Are
“Caeciliidae”, a
paraphyletic group
Northern S. America
Central Africa
SE Asia
Not a lot known
about most of these
animals
Pough et al 2004, Fig 3-12
Pough et al 2004, Fig 3-13
Three Major Clades
Urodela
Photos: KP Bergmann, Pough et al. Fig 3-8
Pough et al 2004, Fig 3-2, 3-5
Urodela
Urodela – refers to crown group salamanders
_________________ – refers to stem group
What species would be included in the
Caudata that are excluded from the Urodela?
Salamanders and newts
Urodela - Synapomorphies
Many obscure
osteological
synapomorphies
Fusion of some bones in
digits I and II
Operculum is fused to
the ear capsule
Quadratojugals are
absent
2nd Ceratobranchial
bone is lost at
metamorphosis
Duellman & Trueb 1994, Fig. 13.1
1
Urodela – General features
Most species have a
generalized
morphology:
Urodela – General features
Four limbs
______________
Long tail
______________
Some trends towards
limb reduction and
body elongation
(Sirenidae,
Amphiumidae)
Most species are
terrestrial
Some arboreal, some
aquatic
All rely on water for
reproduction
Have mucous & poison
glands
Ambystoma californiense
Glands also produce
________________
___________ glands
are used in courtship
Stebbins and Cohen, 1995, Fig. 17.3
Urodela – Reproduction
Often have elaborate
courtship rituals
Most have internal
fertilization
Urodela – Reproduction
female
Larvae similar to
adults (compared to
other amphibians)
Larvae have external
gills and slits
How are these larvae
adapted to their
habitats?
male
Pond Dweller
Use a ______________
No intromittent organ
Larval stage as well as
direct development
(Plethodontindae) are
common
Stream Dweller
Terrestrial Direct – Developer
Duellman and Trueb, 1986
Stebbin & Cohn 1995, Fig 17.16
2
Urodela – Defense
Urodela – Other Information
Many behavioral antipredator adaptations
Large _____________
_________________
Paedomorphosis is
common
Echinotriton chinhaiensis © Max Sparreboom
10 major clades
516 species
4 species in SE USA
______________ lineage
___________ & limb reduced
Fully ______________
Prey on insects, crayfish, worms
Oviparous – lay eggs
Synapomorphies
Reanalysis of rRNA
and morphological
data
Uncertainty of
position of Sirenidae
Urodela – Sirenidae
Paedomorphic features
Phylogeny
controversial
In some species, all
adults retain larval
characters
In others, only some
adults retain larval
characters
Duellman and Trueb, 1986
Urodela – Phylogeny & Diversity
Largest among
vertebrates
Cells are large to
contain all the DNA
Basal vs. near
Proteidae
No pelvic girdle or hind limbs
Keratinized beak replaces
premaxillary teeth
Non-pedicellate teeth
Pough et al. 2004, Fig 3-1
Pough et al. 2004, Fig 3-2a
Urodela – Cryptobranchoidea
Includes
Urodela – Cryptobranchidae
Cryptobranchidae
Hynobiidae
3 species in Japan, China, and
Eastern USA
Hellbender
Synapomorphies
Sister to
Salamandroidea
Synapomorphies
_____________ ribs
_________ that secrete
into cloaca
Fusion of some hyoid
bones
Pough et al. 2004, Fig 3-1
No ______________
External gills
Reduced number of toes
on the front limbs
Have ___________ bodies
and heads
_____________
Largest – up to 1.8 m!
Males make nests and guard
nests
Live in cold mountain streams
Rely on _______________
respiration (skin folds)
Lack eye lids
One set of _________
These are
paedomorphic traits
**Lateral skin folds
© Dr. Eric J. Routman
1
Urodela – Salamandroidea
Includes all other
Urodela
3 species in SE USA
Elongate and limb-reduced
Paedomorphic
Have remnants of all 4 limbs
Synapomorphy
Urodela – Amphiumidae
Lack eyelids
Have gill slits (but lack external
gills – distinguish from Sirenids
Females have a
________________,
which stores sperm
after insemination
Aquatic ________________
Vertebrates and inverts
Powerful, muscular jaws
Oviparous
Large – up to over a meter
Pough et al. 2004, Fig 3-1
Duellman & Trueb 1994, Fig. 13-6
Urodela –
Plethodontidae
Diverse: 360 species
Coastal western USA
Eastern USA
Mexico to Brazil
Italy
© John White
Urodela – Plethodontidae
Only salamanders to
radiate in ___________
Highly variable
Subterranean, aquatic,
terrestrial and arboreal
Life history varied
Some forms with webbed
feet, prehensile tails
Often small
Pough et al. 2004, Fig 3-5
Pough et al. 2004, Fig 3-7
Urodela – Plethodontidae
5 species in Massachusetts
Urodela – Proteidae
6 species in E USA & Balkans
Aquatic – large permanent
bodies of water
Large – up to 45 cm
Synapomorphies
Including Plethodon cinereus
Proteus anguinus
Synapomorphies
________________ (cutaneous
respiration)
__________________________
Lacrimals & pterygoids absent
No operculum
Photos: PJB, Stebbins and Cohen 1995, Fig 7-2
No _________________
External gills and gill slits
(paedomorphic)
2n=38 (other Urodela have
30 chromosomes)
Pough et al. 2004, Fig 3-2d
2
Urodela – Salamandridae
62 species
Coastal USA and Canada
Europe & Northern Africa
China & Japan
Urodela – Salamandridae
Many species _____________
Includes “____________”
Some have rugose skin
Unken reflex for defense
Tetrodotoxins
Massachusets species:
Nothophthalmus viridescens
Complex life cycle
Pough et al. 2004, Fig 3-3
Metamorphosis 1: Larva to Eft
Metamorphosis 2: Eft to Adult
Aquatic terrestrial aquatic
Photos © PJB, H Greene
Urodela – Ambystomatidae
30 species in N. America
Robust body
Some terrestrial, some aquatic
___________ is paedomorphic
Some hybridize and are
unisexual and parthenogenetic
Variable ploidy level
Four species in Massachusetts
Pough et al. 2004, Fig 3-2e
3
Clades of Urodela Covered in Lecture
Clade
- Sirenidae
CRYPTOBRANCHOIDEA
- Cryptobranchidae
SALAMANDROIDEA
- Amphiumidae
- Plethodontidae
- Proteidae
- Salamanridae
- Ambystomatidae
#
spp
Distribution
Synapomorphies
Habitat
Paedomorphic?
Other Notes
Anura
Three Major Clades
Pough et al. 2004, PJB
Photos: KP Bergmann, Pough et al. Fig 3-8
Anura
Anura
Anura – Crown group frogs
_____________ – Stem group frogs,
so includes fossil forms as well
Anura is our focus in this course
Evolved in the Cretaceous
Triadibatrachus is sister group to Anura, from Lower Triassic
~12 presacral vertebrae instead of 8-9
Had a ________________, composed of _________________
Pough et al. 2004, Fig. 3-19
Anuran Synapomorphies
_________ presacral vertebrae
________________
Hindlimbs > Forelimbs
______________ bone: Ulna &
radius fused
______________ bone: Tibia &
fibula fused
Elongate ankles
Fused bones in skull
How are these adaptations for
jumping?
Pough et al 2004, Fig 3-14
1
Anura – Specialized Jumpers
Adaptations?
What they do
9 presacral vertebrae
Urostyle
Hindlimbs > Forelimbs
Ulna & radius fused
Tibia & fibula fused
Elongate ankles
Fused bones in skull
Anura – Specialized Jumpers
Fusion and reduction
of skull
_____________
Also, ribs are
reduced or lost
Caecilian
Lightens body
Allows vertebrae to
be more _________
Less protection of
organs
Salamander
Frog
Zug et al. 2001, Fig 2.10
1
Anura – Specialized Jumpers
Anura – Specialized Jumpers?
Exceptions:
Jumping likely originated as
______________________
Today, most frogs are
specialized jumpers
Jump as a form of
________________
Many are not very good at
walking
All of these can still jump,
but not well
Rely more on walking or
swimming
Hind limbs too long
Body not flexible
Heavy horned frogs
Short limbed toads
(Bufonidae)
Some aquatic specialists
(Pipa, Xenopus)
© National Geographic, B Lavies
© KP Bergmann
Anura – Skin
Anura – Skin
The skin of frogs serves
many important functions
Mucous glands
____________ glands
___________________
Water balance
___________________
Reproduction
___________________
Defense
Mucous Glands
prevent dehydration
Localized to nuptual pads
Sticky – good grip
Sexually dimorphic
Poison/granular Glands
Toxic or noxious secretions
Defensive
© PJB, KP Bergmann
Stebbins & Cohen 1995, Fig. 2.1
Anura – Skin
Anura – Skin
__________________
Xanthophores
Iridiophores
Red & Yellow
Just beneath epidermis
Silver, grey
Deeper than xanthophores
Black
Deepest
Under hormonal control
Stebbins & Cohen 1995, Fig. 2.2
Why is this important to
Plethodontids?
Some species have epidermal
elaborations
Melanophores
Give pigmentation
All amphibians use cutaneous
respiration to some degree
Increased _________________
Increased _________________
Rely on water being abundant
Hairy Frog (Trichobatrachus) Compare to Hellbender
Stebbins & Cohen 1995, Fig. 3.5
1
Anura – Reproduction
Diverse reproductive strategies
Sound production
Anura – Reproduction
______________
Primary mode of ____________
Primarily males, calling for mates
Used in:
L. = embrace, hug
3 Types:
________________
Territory defense
________________
Inguinal
Axillary
Cephalic
Eggs are:
Generally deposited in
water
Deposited on land
Suspended (arboreal)
© KP Bergmann; Stebbins and Cohen, 1995
Anura – Reproduction
Anura – Reproduction
Parental care
Tadpoles and adults are
very distinct
Tadpole
Common
Varied
Egg guarding
Darwin Frog – Young
in vocal sacs
Generally ______________
(algae)
Some are carnivores, some
are __________________
Some do not feed
Adults
Brood
guarding
____________ (insectivores)
Modifications to gut, jaws,
limbs, body shape, tail
Stebbins & Cohen 1995, Fig. 18.2, 18.4
Stebbins & Cohen 1995, Fig. 1.2
Anura – Phylogeny and Diversity
29 major lineages
~4,800 species
Have radiated extensively in the
_______________
Account for the majority of
Lissamphibian diversity
Major clades are characterized
mainly by:
Skull & vertebral characters
_______________ morphology
Limb muscles
_______________ type
Anura – Phylogeny and Diversity
See next Yikes! What a monster!
Note: Poor resolution
among derived groups
Pough et al. 2004, Fig 3-20
2
Anura – Phylogeny
and Diversity
Anura - Ascaphidae
More basal frogs are
better resolved
Successive sister
groups to the
Pipanura (5)
1 species in NW USA,
SW Canada
“Tailed frog”
Tail is extension of
__________, used in
_________________
Inhabit high energy
streams (fast)
Do not call
Lack _____________
Ascaphidae*
Leiopelmatidae
Bombinatoridae*
Discoglossidae
Neobatrachia
* Covered
Pough et al. 2004, Fig 3-20
Anura - Bombinatoridae
http://www.digimorph.org/
Anura – Mesobatrachia
10 species
Europe, E China,
Korea, Philippines
Bombina orientalis
Next most basal clade (6)
Includes:
Bombina – Fire-bellied
toads
Toxic, ____________
Use Unken reflex
Synapomorphies are a
number of skull
characteristics
Pipidae*
Rhinophrynidae
Megalophrydae
Pelodytidae
Pelobatidae*
Synapomorphies:
Skull and hyoid
characters (don’t
need to know them)
Pough et al. 2004, Fig 3-20
Anura – Pelobatidae
11 species
USA, Mexico, Europe
1 MA speices: Scaphiopus holbrookii
Anura – Pipidae
Spadefoot toads
______________ are keratinized
metatarsal tubercles for digging
______________
Often enlarged parotid glands
(convergent with Bufonidae)
Adapted to dry habitats:
Aestivate
Explosive breeders
Fast development (egg to
metamorphosis in ~8 days)
30 species
Amazon, sub-saharan Africa
_____________
Dorsoventrally compressed
_______________________
Eggs develop in swollen skin
of female’s back
Xenopus a model species
Synapomorphies:
Non-pedicellate teeth
No tongue
______________________
© P Corasaro; Pough et al. 2004, Fig 3-23f
3
Anura – Phylogeny
and Diversity
Anura – Bufonidae
More derived groups are
“Bufonoidea” and Ranoidea
“Bufonoidea” are probably
paraphyletic
Together, they make up
Neobatrachia (10)
~450 species
Cosmopolitan, except Sahara, Australia,
Papua New Guinea, and extreme north
Pough et al. 2004, Fig 3-20
Pough et al. 2004, Fig 3-27
Anura – Bufonidae
______________
Walk and hop
Short legs
Includes cane toad, Bufo
marinus, introduced to
Australia
835 species
Americas, Europe, Middle East, China, Japan, Papua
NG, Australia
Synapomorphies:
Anura – “Hylidae”
No teeth
_______________ glands
Bidder’s organ (rudimentary
ovaries on male’s testes)
2 MA species: Anaxyrus
americanus & A. fowleri
Pough et al. 2004, Fig 3-27
Anura – “Hylidae”
Anura – “Leptodactylidae”
2 MA species
Mainly arboreal
_______________ on digits
Claw shaped terminal
phalanges
Have radiated mainly in
Neotropics
>1,100 spp.
South America, Middle
America, Caribbean
No synapomorphies
Very diverse
Includes most species rich
vertebrate genus
Phyllomedusa have lipid
glands and use a wiping
behavior to spread lipids on
the body to prevent
desiccation
Photos PJB
Eleutherodactylus >700
species!
Also includes Ceratophrys,
horned frogs
© J Milmoe, KP Bergmann
4
Anura – Myobatrachidae
Anura – Phylogeny and Diversity
122 species
Australia & PNG
2 spp with female
________________
1 sp with male inguinal
pouches for young
Synapomorphies are
sperm characteristics
Ranoidea is monophyletic
Synapomorphies have to
do with pectoral girdle
Pough et al. 2004, Fig 3-21
Pough et al. 2004, Fig 3-17, 3-20
Anura – “Ranidae”
Anura – Dendrobatidae
>600 spp
Cosmopolitan, except
islands, Sahara, Australia,
extreme North & South
Another paraphyletic group
with no synapomorphies
Highly variable
5 MA species, including
Bullfrog & Leopard Frog
205 species
Central America, N. half of
S. America
Use __________ amplexus
Carry larvae – parental care
Aposematic and highly toxic
Poison is dietary (ants,
millipedes)
__________ and terrestrial
Synapomorphy: Dermal
scutes on dorsal surface of
fingers
PJB; Pough et al. 2004, Fig 3-28c
Anura – Mantellidae
140 species
Madagascar
Defined solely by ______________________
Primarily terrestrial, small
_________________ coloration
Lipophilic skin alkaloids (convergent with Dendrobatids)
Ecologically diverse
Anura – Rhacophoridae
300 species
Central Africa, SE Asia, Japan
Rhacophoridae
Pough et al. 2004, Fig 3-30e,f
Pough et al. 2004, Fig 3-22
5
Anura – Rhacophoridae
Mostly arboreal
Enlarged toe pads
Some are _________,
with large membranes
between digits
Some with foam nests
and communal nests
Primarily muscle
synapomorphies
Photo © T Laman
6
Clades of Anura Covered in Lecture
Clade
- Ascaphidae
- Bombinatoridae
MESOBATRACHIA
- Pelobatidae
- Pipidae
BUFONOIDEA
- Bufonidae
- “Hylidae”
#
Spp
Distribution
Synapomorphies
Habitat
Other Notes
- “Leptodactylidae”
- Myobatrachidae
RANOIDEA
- “Ranidae”
- Dendrobatidae
- Mantellidae
- Rhacophoridae