amphibians lecture

Herpetology

The study of reptiles and amphibians.

morphology

not all shared traits useful to determining phylogeny bc diff between homology and analogy

hybrid invariability

developmental problems in hybrid cause reduced survival

Ectothermic

Organisms that derive their energy from outside their bodies.

cons: ability to be warm may be sacrificed to stay wet, limited activity, heat loss by convection

pros: longer fasting, can inhabit food poor and variable enviros, most energy goes to other needs (growth and reproduction), greater capacity to be smaller, stable populations, can utilize small prey

behavioral thermoregulation: huddling, basking, can retain body temp by cutting blood flow to limbs allowing fluctuations in core temp that would kill mammals

Poikilothermy

An irregular body temperature that varies with the environment.

homeothermy

stable body temp

Amphibians

A class of ectothermic vertebrates that typically undergo metamorphosis and include frogs, salamanders, and caecilians.

Order Caudata

The order of amphibians known as salamanders.

Order Anura

The order of amphibians that includes frogs and toads.

Order Gymnophiona

The order of amphibians that includes caecilians, characterized by their snake-like appearance.

Cladistics

A method of classifying organisms based on common ancestry and evolutionary relationships.

assumes things change over time, organism is related to another by common organism, lineages bifurcate

Synapomorphy

A derived characteristic shared exclusively by evolutionary descendants and ancestor

Biological Species Concept

Defines a species as a group of interbreeding populations that are reproductively isolated from other such groups.

Amniotic Egg

An egg that has protective membranes and allows for reproduction on land.

Tetrapods

Four-limbed vertebrates that include amphibians, birds, reptiles, and mammals.

Nomenclature

A system of names used in a particular field or community.

Mitochondrial DNA

DNA found in the mitochondria used in genetic studies, particularly in species classification.

Morphological Species Concept

A concept that identifies species based on measurable physical traits.

Phylogenetic Tree

A diagram representing the evolutionary relationships among species.

tips: taxa under study (species or species groups)

branches: genetic divergence of taxa from its most recent ancestor

node: point where bifurcation happens

root: shows oldest common ancestor of all taxa on tree

phylogenetics

study of evolutionary history of species or grou; of species

polytomy

node where 3 branches, implies lack of clarity on order groups diverged

monophyletic

ancestor and all descendants

paraphyletic

ancestor and some descendants

polyphyletic

species w diff recent common ancestor

Ectothermy vs. Endothermy

Ectothermy is when an organism's body temperature is regulated by external factors, while endothermy is the regulation of body temperature through internal metabolic processes.

Cryptic Species

Species that are ecologically distinct but look similar and can hybridize.

Allopatric Speciation

The formation of new species through geographical separation from its ancestor

Parapatric Speciation

Speciation that occurs when populations are separated by environmental boundary (sharp transition)

reinforcement: selection against mating w other form (pre-zygotic)

Sympatric Speciation

The evolution of new species from a single ancestral species while inhabiting the same geographic region.

Tiktalik

An important transitional fossil linking fish and tetrapods discovered in Canada.

not true tetrapod just had well developed limbs but no attached girdles (attached to spine in true tetrapod, allows to push up and down, and gives greater locomotion)

Cutaneous Respiration

Breathing through the skin, common in amphibians.

Pedicellate Teeth

Teeth in amphibians composed of a basal pedicel and a distal crown.

Direct Development

A type of development in which the young resemble the adult form without a larval stage.

Paedomorphosis

The retention of juvenile traits in the adult form.

Tenremes

A group of mammals characterized by their long snouts and insectivorous diet.

Biodiversity

The variety of life in the world or in a particular habitat or ecosystem.

Amphibious

Adapted to live both on land and in water.

Fossil Gap

A discontinuity in the fossil record where few or no fossils exist from certain time periods.

Acoustic Communication

Behavioral trait in amphibians where sounds are used for mating and territory establishment.

is the gopher frog (Rana capito) characterized as a species of special concern

YES

what frog in florida is exception to rule of egg to tadpole to frog development?

greenhouse frog

what glands secrete poison in cane toads?

paratoid glands

how to tell the difference between a siren and an amphiuma?

sirens have 2 front limbs while amphiumas have 4

what does red eft stage refer to?

juvenile stage of an eastern newt

Eating a dozen salamanders from this most toxic family could make you very ill or kill you

Salamandridae

Very long ilia (1 of 3 paired bones that make up pelvic girdle, or hip bones, are characteristic of

Anura

The unisexual triploid Ambystoma usually reproduce by gynogenesis, which is:

Mating with diploid males but not incorporating their DNA into the offspring

Internal fertilization in salamanders usually occurs by means of a

spermatophore

The primary habitat of the first Devonian tetrapods is thought to have been

water

why are amphibians and reptiles grouped together?

ectothermic vertebrates

Ross Allen

everglades rat snake named after him

Bill Haas

miami serpentarium, pioneered venom milking and anti venom, controversially practiced self envenoming

Archie Carr National Wildlife Refuge

major sea turtle nesting site

Walter Auffenberg

monitor and iguana conservation

Lora Smith

technically outside of FL, gopher tortoise research methods

heart w 2 auricles, 2 ventricles, warm red blood

viviparous: mammals

oviparous: avians

heart w 1 auricle, 1 ventricle, cold red blood

lungs voluntary: amphibians

reptiles (lizards, frogs)

serpents (amphisbaenians, snakes)

nantes: everything not grouped above

external gills: fish

heart w 1 auricle, 0 ventricles, cold pus like blood

antennae: insect

tentacles: vermes from arthropod invertebrates

tetrapoda- four legs: birds, reptiles, amphibians

evolved ~400 mya, many traits not initially derived to live on land

punctuated equilibrium hypothesis

evolutionary development is marked by isolated episodes of rapid speciation between long periods of little/no change. once species appears in fossil record the population will become stable, showing little evolutionary change

loss of opercular bone between pectoral girdle and skull

allows for head movement independent of body, allows for better head movement in shallow water to try to capture prey without need to move entire body

zygapophyses

add stability during movement to axial skeletons, is one of 2 paired processes of vertebra that interlock it w adjacent vertebra, help guide movement of vertebral column and protect spinal cord

early tetrapodomorphs

lived in aquatic shallows w useful adaptations to potential life on land

-benefits of living in shallow:

-escape predation from large fish

-reduce predation of eggs

-exploit unfilled niches

-better thermoregulation

reasons to leave water

-Devonian: early plants, facilitated by fungi, colonized land and led to anoxia (lack of oxygen) and went up to land for more O2

-overland movement to escape drying enviros

-new habitats w few competitors

-juvenile dispersal

-search for safer location to lay eggs

-basking in sun increased thermoregulation

Tungsenia paradoxa

earliest known “finned stem-teirapod”, from lower devonian (409 mya) of china

Romer’s gap

fossil gap between early and modern tetrapods (~30 mil years), early tetrapods had 8 but modern have 5

Perderpes helps fill gap

operculum muscle

attachment to suprascapula, allows them to feel sound through legs

levator bulbi muscle

muscle in amphibian eye socket and pushes eyes downward to move food down throat and elevates eye

anthracosaurs

main adaptation: amniotic egg

anapsia: extinct

synapsid: early mammal like and mammal ancestors

diapsid: birds and modern reptiles

hemipenes define lepidosaurs (lizards and snakes)

archosaurs and testuoines have single copulatory organs, turtles are archosaur or just outside

amphibians

8715 species, 74 families

Anura (without tail)

7678 species, 54 families

frogs and toads

under clade Salienta

Caudata (having tail)

salamanders

Urodela (tail visible) is commonly used for crown group and Caudata is total group

816 species, 10 families

Gymnophiona (naked snake)/Apoda (without foot)

221 species, 10 families

Caecilians

frogs and salamanders split 250 mya, proto-frogs appear in early Triassic, 1st true frogs and salamanders in early Jurassic

• Doleserpeton

  • temnospondyli

  • lower permian, oklahoma (250-270 MYA)

  • pedicellate teeth

  • Dissorophidae

  • ancestor to Lissamphibia (mid-Permian)

• Gerobatrachus hottoni

  • Permian (290 MYA)

  • characteristics of both salamanders and frogs, creates arguments of monophyly

first true salamanders

Marmorerpeton: early neoteny, Karauridae (Karaurus sharovi)

extant family of salamanders in late Cretaceous

first Caecilians

Eocaecilia micropodia

still has feet

early Jurassic (190 MYA), US

Triadobatrachus massinoti

one of earliest lissamphibia

lower triassic

ancient frogs

• Prosalirus bitis: from NA, suggests ancestors of Lissamphibia

• Dicroglossidae: oldest extant frog family

is Lissamphibia monophyletic?

fossil gap and morphologically/ development male it hard to tell, some develop directly, gastroincubation, viviparous eggs

however, have shared derived traits like pedicellate teeth, green rods

class Amphibia

• tetrapod vertebrates that pass through larval stage and undergo metamorphosis into terrestrial adults

• some have <4 limbs

• direct development-larvae develop in egg

• paedomorphosis- do not metamorphose

paedomorphosis

adult retains juvenile traits

paedogenesis

when a juvenile reproduces

class Amphibia synapomorphies

1. amniotic egg (gelatinous capsules, embryo, yolk), no amnion (sac filled w amniotic fluid which protects embryo, chorion plays key role in blood and gas between mother and fetus, develops into fetal aspect of placenta, allantois- respiratory organ and excreta resevoir)

2. scales and claws absent

   • pipidae claws made of bone not keratin

3. 10 pairs of cranial nerves

4. 2 occipital condyles articulate w 1st cervical vertebra- Atlas (upward/downward but not side to side movement)

5. 1 sacral vertebra (sacrum)- enlarges transverse (90 degrees) processes (diapophyses) articulate w pelvic girdle

6. teeth

   • homodont (structurally uniform)

   • polyphyodont (continually replaced)

   • pedicellate- divided into a basal pedicel and distal crown

7. 3 chambered heart (2 atria, 1 ventricle)

8. 2 types of multicellular glands

   • mucous

   • poison (granular)

9. cutaneous respiration

10. gilled larval stage, metamorphosis

    • internal (tadpoles), external ( axololts)

11. reduced number of cranial bones (no tabular, temporal, supraoccipital, basoccipital, jugal, postorbital)

12. amphibian papilla (papilla amphibiorum)- sensory region in inner ear for low frequency sounds

13. opercular bone in inner ear, connected by muscle to pectoral girdle, transmits low frequency vibrations from legs to amphibian papilla

    • tympanum, stapes transmit high frequencies

    • tympana lacking in salamanders, caecilians, and some frogs

14. green rods in retina (except caecilians), also have red rods, single cones, double cones, limited color vision

15. levator bulbi muscle- elevates eye

16. fat bodies associated anatomically, physiologically, and developmentally w gonads

17. unique chromosomes/DNA patters, reduced number of chromosomes, increase in nuclear DNA, high interspecific variability in genome size

amphibian skin

• larvae: skin is 3-5 layers, is highly vascularized, and living

• adults: 5-7 layers, dead keratinized layer, thicker skin less likely to be used for gas exchange

• breeding + reproduction: may have nuptial pads to hang onto females, can direct pheromones towards females, may brood young in skin

amphibian respiration

• gills (atleast as larvae)

• lungs (the Hyobrachial apparatus)

• skin: most CO2 loss, more prone to dessication, needs to be very vascularized

heterochromy in amphibians

alteration of development rates of body tissue

paedomorphic- as adult, retain juvenile traits, has same age to reach maturity

paedogenic (paedotypic)- accelerates reproductive tissues so it can reproduce while looking like juvenile

courtship in amphibians

• anurans: very complex and often driven by audio communication

• salamanders: very complex due to variability in internal vs external fertilization, involves highly derived chemical intra specific communication

• caecilians: not much known due to their secretivity

amphibian reproduction

• frogs: almost exclusively external fertilization

• salamanders: 3 families w external fertilization, most internal, typically don’t have copulatory organ genetic transfer facilitated through spermatophore

• caecilians: almost exclusively internal fertilization, have phallodeum (copulatory organ, part of cloaca) and specialized glands (male Mullerian glands) to facilitate sperm transfer

  • aquatic larvae or direct development

amphibian parental care

• anurans: from no involvement to care until metamorphosis

• salamanders: primarily not involved but some nest guard

• caecilians: some have no involvement, but group typically invests a lot of resources

salamander synapomorphies

1. adults possess long, well developed tail

2. forelimbs always present and hind limbs typically present'

3. forelimbs and hindlimbs same size

4. no tympanum or middle ear cavities

5. many skeletal elements cartilaginous, skull, between vertebrae, pelvic and pectoral girdles

6. most have opisthocoelous vertebrae (anterior of centrum convex, posterior concave), some amphicoelous (both surfaces concave)

7. larval gills external and larvae possess 3 pairs of gills

   • pond type: large feathery gills, low O2, extensive respiratory surfaces (Ambystoma

   • stream type: reduced gills, live in cool water w high O2 content (Gyrinophilus)

   • mountain brook type: atrophied gills, rich O2, respiration primarily cutaneous (Desmognathus)

8. larvae possess true teeth

9. primarily in northern temperate zones

10. fertilization internal (derived lineages) or external (basal lineages), internal fertilization by female picking up spermatophore, no copulatory organ

11. aquatic or terrestrial (or both)

12. development direct or indirect (via larval stage)

13. paedomorphosis (interspecific, between species)/paedogenesis: when juvenile organism reproduces (intraspecific, within species)

hybridogenesis

maintenance of an interspecific hybrid lineage by having hybrids exclude the chromosome set of one parental species

Caecilian synapomorphies

1. no limbs or limb girdles present

2. burrowing mode of life, in most soil, some aquatic (with fins)

3. unusual sense organ: retractable tentacle, one on each side of head, present only in caecilians, outgrowth of brain emerges from eye socket or hole in skull between eye socket and nostril, olfactory in function, incorporates some eye structure

4. skull in compact solid structure compares to skulls of other amphibians which have many fenestrations- extensive fusion of cranial elements, presumably related to burrowing habits (do have lower and upper teeth)

5. eyes small to vestigial- no eyelids, eyes buried under skin or under bone

6. left lung often rudimentary, 2 species known to be lungless (Caecilita iwokramae and Atrectochoana eiselti)

7. body ringed with primary folds (annuli)- then secondary folds in some. makes segments, each associated w 1 vertebra

8. tiny dermal scales in folds, only scales found in amphibians (not in all groups)

9. no external ear openings, but can hear low frequency sounds transmitted through skull to inner ear

10. distributed worldwide in tropics (except Madagascar and Australia)

Caecilian reproduction

• 70% oviparous- female guards eggs

• aquatic larvae or direct development

• some young feed on mother’s skin or skin secretion

• some families exhibit viviparity, development of embryo inside mother

• phallodeum- copulatory organ, part of cloaca

• male mullerian glands- enhance fluid transport of sperm

Caecilians

• 225 species, 10 families

• viewed as poorly diversified, primitive group

• families

  • Rhinatrematidae

    • 3 genera, 14 species

    • northern SA

    • considered most basal family

  • Ichthyophiidae

    • 2 genera, 58 species

    • SE asia, india, and sri lanka

  • Caeciliidae

    • 2 genera, 51 species

    • central and SA

    • more specialized for burrowing

  • Typhlonectidae

    • 5 genera, 14 species

    • tropical SA

    • specialized aquatic forms

    • tail absent

    • no secondary folds- no scales

    • both lungs well developed- diff from all other caecilians

  • Scolecomorphidae

    • 2 genera, 6 species

    • Africa

    • tail absent

    • secondary folds and scales absent

Anuran key characteristics

1. reduced amount of vertebrae (5-9 presacral vertebrae)

2. limb specialization

   • long hind limbs and short front limbs

   • fused specialized bones include tibio-fibula, radio-ulna, urostyle which allows for force absorption when jumping

   • adults- no lower teeth, broad skull w few bones

   • larvae have internal gills, lack true teeth

3. highly variable life histories, tadpoles vs direct developers

4. external fertilization, inguinal, pectoral, cephalic

5. auditory communication incredibly important

Anuran tadpole body plan

• type 1

  • jaws not specialized for feeding

  • separate brachial w 2 external openings

  • forelimbs develop posterior to brachial

• type 2

  • simple modification of jaw

• type 3

  • specialized jaw structure w keratin sheath

• type 4

  • more specialized