amphibians lecture

Study of reptiles and amphibians, “herpes” meaning creeping or crawling thing

Carl Linnaeus called them foul creatures and why god did not make many of them

Combined these 2 groups in systema naturae in 1735

Amphibians and reptiles also grouped together for other reasons

Both ectothermic vertebrates

Ectothermy: energy derived from outside body

Ability to stay warm may be sacrificed to stay wet

Behavoiral thermoregulation like huddling and basking

Have ability to retain body temp once gained scha as cutting blood flow to limbs

Diff from cold blooded

Poikilothermy: irregular body temp

The smaller the less stable

Homeothermy: stable body temp

Amphibian biodiversity

Amphibious, “double life”

8715 species

74 families

Florida gofer frog!!! Profs fav

Salamanders, order Caudata “having tail”

Urodela “tail visible”

816 species, 10 families

Frogs+Toads, order Anura “without tail”

Salientia “jumping”

7678 species, 54 families (38 in 2012)

Caecilians, order Gymnophiona “naked snake”

Apoda “without food”

221 species, 10 families

Reptilian biodiversity

12060 species (dec 2022) my birthday :0

Turtles, order Testudines “ tortoises”

Chelonia

361 species, 14 families

Crocs+Alligators, order Crocodylia “lizard”

27 species, 3? Families

Tuatara, order Rhynchocephalia “nose head”

Order Sphenodontida “wedge tooth”

1 species, 1 family

Lizards, snakes, amphisbaenians, order Squamata “scaly”

Suborder (clade) amphisbaenia, worm lizards usually legless

202 species, 6 fam

Lizards, SUB order lacertilia (sauria) “paraphyletic”

7396 species, 37 fam (29 in 2012)

Snakes, SUB order serpentes (ophidia) “monophyletic”

4073 species, 30 families

Herpetology in Florida

3 primary ecoregions w high biodiversity

142 native species, 56 established non native species (2012)

Several famous herpetologists that have defined our history as a state

Ross Allen

Bill Haas

Archie Carr

Walter Auffenberg

“Doc” Erhart

Lora Smith

Intro to Cladistics and Systematics

History of bio organization

Carl Linnaeus (1600s)

Created modern taxonomic system that we use today

Used binomial nomenclature approach to classify organisms, first word genus CAPITAL second word species

Originally had 6 classes

Linnaeus’s 6 animal classes

Heart w 2 auricles, 2 ventricles, warm, red blood

Viviparous: mammalia

Oviparous: aves

Heart w 1 auricle, 1 ventricle, cold, red blooded

Lungs voluntary: amphibia

External gills: pisces

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

Have antennae: insecta

Have tentacles: vermes

Linnaeus ten split Amphibia into 3 orders, not reflective of our modern understanding

Reptiles

Lizards

Frogs

Serpentes

Snakes

Amphisbaenids

Nantes

Anything not in above groups

a species taxon as a group of organisms that can successfully interbreed and produce fertile offspring

26 different definitions of species

Most modern taxonomists tend to follow combo of phylogenetic and morphological approaches to generally classify organisms into clades

Which definition of species do we tend to use

Biological species concept: species is a group of interbreeding populations (or that have potential to interbreed) which is reproductively isolated from other such groups

Phylogenetic species concept: smallest monophyletic group of individuals distinguished by synapomorphies)

Morphological species concept: species recognized based on measurable physical differences

Some species hybridize well but are ecologically distinct, “cryptic” species, odd reproduction strategies (unisexual salamanders)

Taxonomy vs cladistics

Most modern herps use a cladistics based approach to understand bio organization

Traditional taxonomy

Taxas organized in categories

Levels imply relatedness of taxa, have no defined criteria

More of tradition than scientifically valid

Only what constitutes a species is defined

Cladistics: hypothetical depiction of evo relationships among taxa groups

Assuming things change over time, only organism is related yo another by a common organism, lineages generally bifurcate

If species bifurcate we do not see billions bc animals become extinct (99%), this comes as inability to compete

Phylogenetics: study of evolutionary history of species or group of species

Phylogeny: evolutionary history of species or group of species

Phylogenetic tree

Tips: taxa under study

Branches: genetic divergence of taxa from its most recent ancestor

Node: point where 1 group splits into 2+

Root: node that depicts oldest common ancestor of all taxa on tree

Sister taxa: groups with same recent common ancestor

Polytomy: node where 3+ branches emerge, implies lack of clarity on order that groups diverged

Monophyletic group: clade that includes an ancestral species and all its descendants

Paraphyletic group: includes an ancestral species and some but not all descendants

Polyphyletic group: includes members with diff recent common ancestors

What data splits these groups

Morphology:

Homology (homologous trait)-common traits due to shared evolution

Analogy (analogous trait)- common trait due to convergent evolution

genetics/genomics

How are new species created

Prevent gene flow

Isolating mechanisms

Geographical

Biological

Pre zygotic (differences in breeding seasons or courtship rituals)

Post zygotic (hybrid inviability or sterility)

Types of speciation

Allopatric: new species forms geographically apart from its ancestors

Parapatric: new species forms in a contiguous population

Divergence on each side on environmental boundary, hybrid zone, reinforcement-selection against mating with other form (pre zygotic)

Sympatric: new species emerges from within geographic range of its ancestors

Discussion: Anacondas

Am i reading a whole lot of nothing rn?

Debating on how to properly name anacondas taxonomically vs nomenclaturely

Taking into account ethical and societal concerns

Immortalized due to large size and presence in hollywood movies in 19th century led to multiple taxon names

Rivas et al revealed small diff in species but lacked clear species hypothesis and relied on insufficient evidence

mtDNA not enough, describing new species based solely on mitochondrial divergence is inappropriate even considered scientific malpractice

Paial et al and puillandre provided excellent workflow suggestions w mtDNA as hypothesis that can be tested with nuclear genetic markers or morphology

Availability of name ‘akayima’ against code

What evidence and approaches we need

Generate sufficient # of marker to overcome difficulty of dense sampling

Share samples and data in collegial manner to open taxonomic questions without unnecessary duplication

Key lessons

Editors select reviewers with appropriate taxonomic and nomenclatural expertise

Comply fully with taxonomic code

Ensure data justify conclusions

Politics and nomenclature, ‘akayima’ uses indigenous languages

Use of linnaean system

Discussion: What is a Name?

2 key species separated 10 mil years ago, Eunecteds akayima sp nov and Eunectes murinus

Derives akayima name in effort to honor indigenous nations, derived from carib language

Contributes to taxonomic stability of anacondas but advocates for usage of indigenous names in zoological nomenclature by adopting more flexible approach to ICZN and eliminating exclusionary practices in sciences and other disciplines

This paper is more interesting certainly

Love the graphics

Note their shortfallings

Tetrapods

tetrapoda=four legs in greek

Includes all land living vertebrates

Amphibians

Birds

Reptiles

Mammals

Evolution

Long and gradual process over millions of years beginning 400 MYA

Many adaptations not derived initially to life on land but once on land group continued to refine adaptations and radiated out to a number of newly derived niches (punctuated equilibrium)

All these adaptations came bc they were needed by littoral (shallow) water predatory fish

Specific adaptations

Gills and lungs (derived from swim bladders)

Palate and nares morphology (suggests a choana)

Elaboration of girdles/limbs

Elongation of snout

Precursor fish

Coelacanth-”lobe finned” fishes

Dipnoi-”lung” fishes

These species still around in modern versions

Tiktalik

One of earliest transition fossils associated with transition to land, discovered in canada in 2004

Not true tetrapod just well developed limbs

How do we separate tetrapods?

Synapomorphies of tetrapods

Characteristic present in ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants

4 distinct characters found in all tetrapods

Pelvis attached to vertebral column

Loss of opercular bone connection between pectoral girdle and skull

Allows for more head movement independent of body

Zygapophyses add stability during movement to axial skeleton

Guide movement of vertebral column

Orientation and size differs depending on specific section of skeleton

Developed limbs with carpals and tarsals and robust phalanges

Early tetrapodomorphs

Aquatic shallow water predators with useful adaptations to potential life on land

Shallows were easier to escape from larger fish, reduce predation of eggs, exploit other niches, better thermoregualtion

Number of potential hypothesis that explain why they left water

To enable overland movement to escape drying enviros

New habitats with fewer competition

Dispersal of juveniles

Search for safer location to lay eggs

Basking in sun to increase thermoregulation

Earliest known “finned stem tetrapod” Tungsenia paradoxa from lower devonian (409 mya) of China

Acanthostega Ichthyostega, Tulerpeton

Acanthostega had limbs like a fish (similar to Eusthenopteron) except it had digits rather than fin rays at end, did have stapes (tetrapod synapomorphy)

Ichthyostaega also had limbs like tetrapod and probably walked like salamander, bend in limb (elbow or knee) and digits helped limb to make better contact with substrate and pull body up off the substrate

Tulerpeton- most terrestrial with robust shoulder joint and slender digits

Adaptations for terrestrial life

Pre adaptations (exaptions)

Lungs and bucco pharangeal action

Flexible digits

Strengthened

elongate/choana

Adaptations post arrival on land (derivations)

Elaboration of lungs

Enclosed ribs and abdominal pump

Buccal force pumping

Keratinized skin

Evolution of ne sensory systems

Romers gap

Gap between early tetrapods and modern, about 30 million years

Early tetrapods had 8 digits but all modern only had 5

Pederpes helps fill this gap

Major groupings of tetrapods

Temnospondyls

Would become modern amphibians

Dominant group early on, change in topography and position on earth affected ability to do well

Huge

Synapomorphies

2 occipital condyles

Skin with mucus and poison glands

Papilia amphiniorum

Have green rods in eyes

Cutaneous respiration

Pedicellate teeth

Operculum muscle attaches to suprscapula

Levitar bulbi muscle

Those that survived ultimately evolved into Lissamphibia whic include all modern amphibians

Caecillians

Salamanders

Anurans

Antracosaurs

benefited from change in climate that would wiped most of temnospondyls

Main adaptation: amniotic eggs

Synapomorphies

Early lineage had

Thicker skin

Fibrous eggs

Internal fertilization, better prevention of egg desication

Exhibited rounding of skull, made skull stronger more muscle attachment

Ribs begin to appear but don’t fully enclose body cavity until amniotic egg appeears

Gaps in skull appear to make skull less heavy, determines how group is split

Synapsids become mammals

Diapsids become birds and modern reptiles

Transition to modern reptiles

Ultimately split and become what we consider today as modern reptile

Diapsids

Hemipenes define Lepidosauria (lizards and snakes)

Lost internal fertilization then regain it later

Archosaurs and testudines

Have single copulatory organ

Turtles included in archosauria or just outside

Includes turtles, crocs and birds

The Amphibians: Evolution, Physiology, and Taxonomy

Modern amphibians divided into 3 groups

Anurans-frogs

Caudatans- salamanders

Gymnophiona- Caecilians

8715 amphibian species

74 families

Order: Anura “without tail”, frogs

salientia= “jumping”

7678 species

54 families

Order: caudata “having tail”, salamanders

urodela=”tail visible”

816 species

10 families

Order: Gymnophiona “naked snake”, Caecilians

apoda=”without foot”

221 species

10 families

Lissamphibian Evolution

Frogs and salamanders split about 250 million years ago

Proto-frogs appeared in early Triassic

First true frogs and salamanders appeared in early Jurassic

Temnospondyls amphibian Doloserpeton

Lower Permian of Oklahoma (250-270 MYA)

Pedicellate teeth

Family Dissprophidae

Ancestor of Lissamphibia (mid Permian)

Gerobatrachus hottoni

Permian, characteristics of both frogs and salamanders

First salamanders

Marmorerpeton

Middle jurassic, England

Karaurus sharovi

Upper jurassic, Russia

Extant families of salamanders start to appear in late Cretaceous

First caecilian: Eocaecilia micropodia

Early jurassic (190 MYA), U.S.

Earliest Lissamphibian (frog): Triadobatrachus massinoti)

Lower triassic

Oldest family of extant frogs is Discoglossidae

Is lissamphibian monophyletic?

Con:

Fossil gap

Morphological and developmental differences

Pro:

Shared derived traits

Class amphibia

Tetrapod vertebrates that pass through larval state and undergo metamorphosis into terrestrial adults

Some have <4 limbs

Direct development- larvae develop in egg

Paedomorphosis- do not metamorphose

Characteristics of class amphibia!!! (16 synapomorphies)

Amniotic egg (no amnion, chorion, allantois)

Gelatinous capsules, embryo, yolk

Scales and claws absent , except earliest amphibians had dermal scaled, vestigial in caecilians

10 pairs of cranial nerves

2 occipital condyles articulate with 1st cervical vertebra- atlas

upward/downward but not side to side movement

1 sacral vertebra (sacrum)-enlarged transverse processes (diapophyses) articulate with pelvic girdle

Teeth

Homodont (structurally uniform)

Polyphyodont (continually replaced)

Pedicellate- divided into basal pedicel and distal crown

3 chambered heart (2 atria, 1 ventricle)

2 types of multicellular glands

Mucous

Poison (granular)

Cutaneous respiration

Gilled larval stage, metamorphosis

Reduced number of cranial bones (no tabular, temporal, supraoccipital, basoccipital, jugal, postorbital)

Amphibian papilla (papilla amphibiorum)-sensory region in inner ear for low frequency sounds

Opercular bone in inner ear, connected by muscle to pectoral girdle. Transmits low frequency vibration (<1000 HZ) from legs to amphibian papilla

Tympanum, stapes transmit high frequencies

Tympana lacking in salamanders, caecilians, and some frogs

Green rods in retina (except caecilians)

Also have red rods, single cones, double cones

Limited color vision

Levator bulbi muscle- elevates eye

Fat bodies associated anatomically, physiologically, and developmentally with gonads

Unique chromosome/DNA patterns

Reduced number of chromosomes

Increase in nuclear DNA

High interspecific variability in genome size

The Caudatans

Order: Caudata Salamanders “having tail”

Urodela=”tail visible”

816 species, 10 families

Salamander synapomorphies (13 total)

Adults possess long, well developed tail

Forelimbs always present and hind limbs typically present

Forelimbs and hindlimbs approximately same size

No tympanum or middle ear cavities

Many of skeletal elements are cartilaginous, skull, between vertebrae, pelvic and pectoral girdles

Most have opisthocoelous vertebrae

Larval gills are external and larvae possess 3 pairs of gills

Larvae possess true teeth similar but not identical to adult dentition

Primarily in northern temperate zones

Fertilization internal (derived lineages) or external (basal lineages Cryptobranchidae, Hynobiidae, Sirenidae). Internal fertilization by female picking up spermatophore-no copulatory organ

Aquatic or terrestrial (or both)

Development direct or indirect (via larval stage) only 20-25% species have biphasis CLC (most have direct development)

Paedomorphosis (interspecific)/paedogenesis (intraspecific) common- retain larval body form at sexual maturity

Family sirenidae

Genera 2, species 5+

Southeastern USA

2 legs

Permanent larvae (gills, no eyelids)

4 chamber heart

Well developed lungs

Keratinized beak (premaxillary)

Non Pedicellate teeth (splenial, palatine)

External fertilization

Able to reliably aestivate

Suborder Cryptobranchoidea

Current families

Cryptobranchidae

Hynobiidae

Fusion of parts of branchial arches and tibialis muscles

External fertilization- females lack spermathecae

Eggs in paired sacks

Family Hynobiidae