what are amphibians? - clark university · 1 topic 6: amphibian diversity what are amphibians? what...

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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

� The Amphibia is a diverse clade, with many __________ groups

� Extant (crown) amphibians make up the ____________

What are Amphibians?

Benton 1997, Fig 4.21


� Synapomorphies

� Pedicellate, bicuspid teeth

� Ear with stapes and operculum

Pough et al 2004, Fig 2-5



� 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

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:

� Relative hairlessness and upright face of humans

Paedomorphosis

� Paedomorphosis is prevalent in the _______

� Retention of gills in adult axolotl

� Missing late-developing bones

� Large orbits – form early during development

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What are the three major amphibian clades?

� Lissamphibia

� Many synapomorphies

� ~5,300 extant species

� More than Mammalia

� Three Major clades

� ______________: 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

What are the three major amphibian clades?

Major Trends in Lissamphibian Evolution

Body ____________ and stiffening

Microsaur

Anura

Urodela

Gymnophiona

� Body ____________ and limb reduction

Gymnophiona

� Gymnophiona are caecilians

� Highly derived

� Strange morphology

� Elongate and limbless


Gymnophiona – General Features

� Elongate bodies

� ____________, terrestrial, or aquatic

� Aquatic habits are derived

� Many structures are reduced

� ___________

� Limbs

� __________ reduced or absent

Male Typhlonectes(cloaca)

Typhlonectes

Gymnophiona - Synapomorphies

� Annulated bodies

� Annulus – Ring L.

� Homologous with ______________ in Urodela


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� _________________

� Involved in chemoreception

� Contains glands, ducts, and muscles

� Located between eyes and nostrils

� Its position is phylogenetically informative

� Protrusible from the skull

nostril orbitTentacle foramen


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)

� Why would caecilians be less reliant on their lungs than snakes?


� _________________

� A projection of skin from the cloaca in males

� Used as an intromittent organ

� � _______________ fertilization

Typhlonectes(mating)

Male Typhlonectes(cloaca)

Gymnophiona - Reproduction

� Internal fertilization

� 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

Gymnophiona – Scales?

� Deep scales in dermis

� Only in some species – not a synapomorphy

� Only amphibians with scales

� surrounded by poison and mucous glands


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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



Three types of amphibian skulls

______________

• Temporal region open

• Anura & Urodela

______________

• Skull is completely roofed

• Gymnophiona

______________

• Skull is intermediate

• Gymniophiona

Pough et al 2004, Fig 2-6, 3-9

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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

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Gymnophiona – Diversity & Phylogeny

� 6 major clades

� Don’t worry about their names

� 33 genera, 167 spp.

� 109 spp. Are “Caeciliidae”, a paraphyletic group

� Not a lot known about most of these animals


Gymnophiona - Distribution


� Northern S. America

� Central Africa

� SE Asia

Three Major Clades

Photos: KP Bergmann, Pough et al. Fig 3-8

Urodela

� Salamanders and newts

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?

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

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Urodela – General features

� Most species have a generalized morphology:� Four limbs

� ______________

� Long tail

� ______________

� Some trends towards limb reduction and body elongation (Sirenidae, Amphiumidae)

Ambystoma californiense

Urodela – General features

� Most species are terrestrial

� Some arboreal, some aquatic

� All rely on water for reproduction

� Have mucous & poison glands

� 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

� Use a ______________

� No intromittent organ

� Larval stage as well as direct development (Plethodontindae) are common

Duellman and Trueb, 1986

female

male

Urodela – Reproduction

� Larvae similar to adults (compared to other amphibians)

� Larvae have external gills and slits

� How are these larvae adapted to their habitats?

Stebbin & Cohn 1995, Fig 17.16

Pond Dweller

Stream Dweller

Terrestrial Direct – Developer

Pond Dweller

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Urodela – Defense

� Many behavioral anti-predator adaptations

� _________________

Echinotriton chinhaiensis © Max Sparreboom Duellman and Trueb, 1986

Urodela – Other Information

� Large _____________� Largest among vertebrates

� Cells are large to contain all the DNA

� Paedomorphosis is common� In some species, all adults retain larval characters

� In others, only some adults retain larval characters

Urodela – Phylogeny & Diversity

� 10 major clades

� 516 species

� Phylogeny controversial

� Reanalysis of rRNA and morphological data

� Uncertainty of position of Sirenidae

� Basal vs. near Proteidae

Pough et al. 2004, Fig 3-1

Urodela – Sirenidae

� 4 species in SE USA

� ______________ lineage

� ___________ & limb reduced

� Fully ______________

� Prey on insects, crayfish, worms

� Oviparous – lay eggs

� Synapomorphies

� No pelvic girdle or hind limbs

� Keratinized beak replaces premaxillary teeth

� Non-pedicellate teeth

Pough et al. 2004, Fig 3-2a

� Paedomorphic features

� No ______________

� External gills

� Reduced number of toes on the front limbs

Urodela – Cryptobranchoidea

� Includes� Cryptobranchidae

� Hynobiidae

� Sister to Salamandroidea

� Synapomorphies� _____________ ribs

� _________ that secrete into cloaca

� Fusion of some hyoid bones


Urodela – Cryptobranchidae

� 3 species in Japan, China, and Eastern USA

� Hellbender

� 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)

� Synapomorphies

� Lack eye lids

� One set of _________

� These are paedomorphic traits

� **Lateral skin folds

© Dr. Eric J. Routman

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Urodela – Salamandroidea

� Includes all other Urodela

� Synapomorphy

� Females have a ________________, which stores sperm after insemination


Urodela – Amphiumidae

� 3 species in SE USA

� Elongate and limb-reduced� Have remnants of all 4 limbs

� Paedomorphic� Lack eyelids� Have gill slits (but lack external

gills – distinguish from Sirenids

� Aquatic ________________� Vertebrates and inverts� Powerful, muscular jaws

� Oviparous

� Large – up to over a meter

© John White

Duellman & Trueb 1994, Fig. 13-6

Urodela –

Plethodontidae

� Diverse: 360 species

� Coastal western USA

� Eastern USA

� Mexico to Brazil

� Italy


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


Urodela – Plethodontidae

� 5 species in Massachusetts

� Including Plethodon cinereus

� Synapomorphies

� ________________ (cutaneous respiration)

� __________________________

� Lacrimals & pterygoids absent

� No operculum

Photos: PJB, Stebbins and Cohen 1995, Fig 7-2

Urodela – Proteidae

� 6 species in E USA & Balkans

� Aquatic – large permanent bodies of water

� Large – up to 45 cm

� Synapomorphies

� No _________________

� External gills and gill slits (paedomorphic)

� 2n=38 (other Urodela have 30 chromosomes)

Pough et al. 2004, Fig 3-2d

Proteus anguinus

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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

� 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

Clades of Urodela Covered in Lecture Clade #

spp Distribution Synapomorphies Habitat Paedo-

morphic? Other Notes

- Sirenidae

CRYPTO-BRANCHOIDEA

- Cryptobranchidae

SALAMANDROIDEA

- Amphiumidae

- Plethodontidae

- Proteidae

- Salamanridae

- Ambystomatidae

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Three Major Clades

Photos: KP Bergmann, Pough et al. Fig 3-8

Anura

Pough et al. 2004, PJB

Anura

� Anura – Crown group frogs

� _____________ – Stem group frogs, so includes fossil forms as well

� Anura is our focus in this course

Anura

� 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?

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Anura – Specialized Jumpers

� Adaptations?

� 9 presacral vertebrae

� Urostyle

� Hindlimbs > Forelimbs

� Ulna & radius fused

� Tibia & fibula fused

� Elongate ankles

� Fused bones in skull

� What they do


Zug et al. 2001, Fig 2.10

� Fusion and reduction of skull

� _____________

� Also, ribs are reduced or lost

� Lightens body

� Allows vertebrae to be more _________

� Less protection of organs

Caecilian

Salamander

Frog

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© National Geographic, B Lavies

� Jumping likely originated as ______________________

� Today, most frogs are specialized jumpers

� Jump as a form of ________________

� Many are not very good at walking

� Hind limbs too long

� Body not flexible

Anura – Specialized Jumpers?

© KP Bergmann

� Exceptions:

� Heavy horned frogs

� Short limbed toads (Bufonidae)

� Some aquatic specialists (Pipa, Xenopus)

� All of these can still jump, but not well

� Rely more on walking or swimming

Anura – Skin

© PJB, KP Bergmann

� The skin of frogs serves many important functions

� ___________________

� Water balance

� ___________________

� Reproduction

� ___________________

� Defense

Anura – Skin

Stebbins & Cohen 1995, Fig. 2.1

� Mucous Glands

� Mucous glands

� prevent dehydration

� ____________ glands

� Localized to nuptual pads

� Sticky – good grip

� Sexually dimorphic

� Poison/granular Glands

� Toxic or noxious secretions

� Defensive

Anura – Skin


� __________________

� Give pigmentation

� Xanthophores

� Red & Yellow

� Just beneath epidermis

� Iridiophores

� Silver, grey

� Deeper than xanthophores

� Melanophores

� Black

� Deepest

� Under hormonal control

Anura – Skin

� All amphibians use cutaneous respiration to some degree

� Why is this important to Plethodontids?

� Some species have epidermal elaborations

� Increased _________________

� Increased _________________

� Rely on water being abundant

� Hairy Frog (Trichobatrachus) �

� Compare to Hellbender


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Anura – Reproduction

� Diverse reproductive strategies

� Sound production

� Primary mode of ____________

� Primarily males, calling for mates

� Used in:

� ________________

� Territory defense

� ________________


� ______________

� L. = embrace, hug

� 3 Types:

� Inguinal

� Axillary

� Cephalic

� Eggs are:

� Generally deposited in water

� Deposited on land

� Suspended (arboreal)

© KP Bergmann; Stebbins and Cohen, 1995


� Parental care

� Common

� Varied

Stebbins & Cohen 1995, Fig. 18.2, 18.4

Darwin Frog – Young in vocal sacs

Egg guarding

Brood guarding


� Tadpoles and adults are very distinct

� Tadpole

� Generally ______________ (algae)

� Some are carnivores, some are __________________

� Some do not feed

� Adults

� ____________ (insectivores)

� Modifications to gut, jaws, limbs, body shape, tail


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 See next �



� Yikes! What a monster!

Note: Poor resolution among derived groups

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Anura – Phylogeny

and Diversity


� More basal frogs are better resolved

� Successive sister groups to the Pipanura (5)

� Ascaphidae*

� Leiopelmatidae

� Bombinatoridae*

� Discoglossidae

* CoveredNeobatrachia

Anura - Ascaphidae

� 1 species in NW USA, SW Canada

� “Tailed frog”

� Tail is extension of __________, used in _________________

� Inhabit high energy streams (fast)

� Do not call

� Lack _____________

http://www.digimorph.org/

Anura - Bombinatoridae

� 10 species

� Europe, E China, Korea, Philippines

� Bombina – Fire-bellied toads

� Toxic, ____________

� Use Unken reflex

� Synapomorphies are a number of skull characteristics

Bombina orientalis

Anura – Mesobatrachia


� Next most basal clade (6)

� Includes:

� Pipidae*

� Rhinophrynidae

� Megalophrydae

� Pelodytidae

� Pelobatidae*

� Synapomorphies:

� Skull and hyoid characters (don’t need to know them)

Anura – Pelobatidae� 11 species� USA, Mexico, Europe� 1 MA speices: Scaphiopus holbrookii

� 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)

Anura – Pipidae

� 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

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Anura – Phylogeny

and Diversity


� More derived groups are “Bufonoidea” and Ranoidea

� “Bufonoidea” are probably paraphyletic

� Together, they make up Neobatrachia (10)

Anura – Bufonidae

� ~450 species

� Cosmopolitan, except Sahara, Australia, Papua New Guinea, and extreme north


Anura – Bufonidae

� ______________

� Walk and hop

� Short legs

� Includes cane toad, Bufo marinus, introduced to Australia

� Synapomorphies:

� No teeth

� _______________ glands

� Bidder’s organ (rudimentary ovaries on male’s testes)

� 2 MA species: Anaxyrus americanus & A. fowleri

Anura – “Hylidae”

� 835 species

� Americas, Europe, Middle East, China, Japan, Papua NG, Australia


Anura – “Hylidae”

� 2 MA species

� Mainly arboreal

� _______________ on digits

� Claw shaped terminal phalanges

� Have radiated mainly in Neotropics

� Phyllomedusa have lipid glands and use a wiping behavior to spread lipids on the body to prevent desiccation �

Photos PJB

Anura – “Leptodactylidae”

� >1,100 spp.

� South America, Middle America, Caribbean

� No synapomorphies

� Very diverse

� Includes most species rich vertebrate genus� Eleutherodactylus >700

species!

� Also includes Ceratophrys, horned frogs

© J Milmoe, KP Bergmann

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Anura – Myobatrachidae

� 122 species

� Australia & PNG

� 2 spp with female ________________

� 1 sp with male inguinal pouches for young

� Synapomorphies are sperm characteristics



Pough et al. 2004, Fig 3-17, 3-20

� Ranoidea is monophyletic

� Synapomorphies have to do with pectoral girdle

Anura – “Ranidae”

� >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

Anura – Dendrobatidae

� 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

Pough et al. 2004, Fig 3-30e,f

Anura – Rhacophoridae

� 300 species

� Central Africa, SE Asia, Japan


Rhacophoridae

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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

Clades of Anura Covered in Lecture Clade #

Spp Distribution Synapomorphies Habitat Other Notes

- Ascaphidae

- Bombinatoridae

MESOBATRACHIA

- Pelobatidae

- Pipidae

BUFONOIDEA

- Bufonidae

- “Hylidae”

- “Leptodactylidae”

- Myobatrachidae

RANOIDEA

- “Ranidae”

- Dendrobatidae

- Mantellidae

- Rhacophoridae

what are amphibians? - clark university · 1 topic 6: amphibian diversity what are amphibians? what...

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