Phylogeny of Amphibians

Oldest to most recent

1. Lissamphibia

2. Temnospondyli

3. Gymnophiona, Anura, Caudata (extant amphibians)

Why land?

• unexploted food resources

  • aquatic habitat niches already occupied

• lack of large terrestrial predators

  • largely primitive plants & invertebrates

• low O2 in warm H2O (land O2 unlimited)

Early Tetrapods

• Upper Devonian lobe-finned fish

  • pelvic and pectoral fins slowly transition to paired paddles

    • median fins still present

  • small ribcage

• Carboniferous labyrinthodont amphibian

  • paired paddles slowly turn into limbs

  • larger ribcage to account for organs

More Phylogeny (indivudual spp. discussed further below)

• Era: Paleozoic, Period: Devonian

  • Ichthyostega, Tiktaalik

• Era: end of Paleozoic-beginning of Mesozoic, Period: end of Permian-beginning of Triassic

  • Triadobatrachus

• Era: end of Mesozoic-beginning of Cenozoic, Period: end of Cretaceous-beginning of Tertiary

  • Extant salamanders & frogs

• major evolutionary transitions in last 350 years

• Amphibians were the dominant land animals for ~75 million years

Leposondyli

• very small yet very diverse early amphibians

  • similar to newts, eels, snakes, lizards, etc.

Permian era

• droughty conditions

• reptile & early reptile spp. emerged and evolved

Tiktaalik

• late Devonian (375 MYA)

• discovered in Canada in 2004

• predated Ichthyostega by 5 million years

  • thought to be the oldest up til this point

• 1-2m long

• most notable feature: front pair fins with wrist-like structure

• other features

  • spiracles (primitive nostrils)

  • lungs & gills

• 1st tetrapod with proper neck

  • greater flexibility during short bouts on land

Ichthyostega (“roof fish”)

• late Devonian (370 MYA)

• discovered in Greenland

• 5 ft, 50 lbs

• fish & amphibian features

  • webbed feet

• could breathe air for short periods of time

Eryops

• Permian (270 MYA)

• crocodile-like early amphibian

• aquatic & terrestrial

• had some structural features that would appear in later reptiles

Diplocaulus (“double stalk”)

• middle-late Permian (240-230 MYA)

• 3ft, 5-10 lbs

• wide V-shaped boomerang head

• possibly used to navigate strong currents

• facilitated rapid opening for suction-gape feeding

Frog Evolution Trends

• several modifications for jumping

  • vertebral column short & inflexible

    • reduction in presacral vertebrae

      • found within pelvis (cervical, thoracic, lumbar)

    • increase rigidity, absorption of landing

    • transfer energy directly to hind limbs

    • enlarged pelvic girdle, strengthened & anchored to vertebral column

    • no ribs

    • no tail as adult

    • overall body truncated

  • hind limbs elongated for jumping

  • muscles modified for jumping

Amphibamus (“equal legs”)

• late Carboniferous (300 MYA)

• swamps in Europe & NA

• 6 inches, few ounces

• more salamander-like than frog-like

• 33 presacral vertebrae

  • common characteristic of early amphibs (large amount of presacral vertebrae)

Gerobatrachus (“frogmander”)

• early Permian (290 MYA)

• found in Texas in 2008

• why is it called “frogmander?”

  • 2 fused ankle bones

  • backbone intermediate in length

    • decrease from 33 vertebrae in Amphibamus

  • large tympanum (large, external ear on frogs)

  • wide, frog-like skull

• likely transitional

  • 240-275 MYA splitting frogs & salamanders

Triadobatrachus (“proto frog”)

• early Triassic (250 MYA)

• found in Madagascar

• first fossil frog

• characteristics

  • short, stubby tails

  • 10 cm

  • 13-14 presacral vertebrae

    • 9 in modern frogs

Viraella

• early Jurassic (~200 MYA)

• found in Argentina

• earliest “true” frog

• may belong to Leiopelmatidae (modern family)

• classic frog-like head & large eyes

• legs modified for jumping (explored in next point)

Triadobatrachus vs. Viraella

• Vieraella more truncated overall

  • reduction in presacral vertebrae

  • enlarged & fused pelvic bones in Viraella

  • fused tibiofibula in Viraella

Paleobatrachus (“ancient frog”)

• Cretaceous--Tertiary (130-135 MYA)

• found in Europe

• completely aquatic

  • inhabited swamp basins

  • volcanic gases preserved soft tissue

• resembles present day Xenopus

Amphibians vs. Reptiles

• amphibians

  • clawless

  • scaleless

  • moist skin (respiration)

  • unshelled eggs

• reptiles

  • limbs & muscles

  • increased brain size (cerebrum & cerebellum)

  • more effective jaw

  • skeletal structure improved

  • skin toughened with scales

    • reduced cutaneous respiration

  • well-developed lungs

    • consequence of scales

  • amniote egg

    • no longer relied on water for breeding

  • arose from anthracosaurs (later tetrapods)

Order Caudata (Salamanders)

• characteristics

  • smooth skin

  • long tails

  • long cylindrical bodies

  • most have 2 pairs of very well developed limbs

  • some have nasolabial groove

    • little groove that runs from nose to lips

  • costal grooves

    • body folds found on their sides

  • carniverous & cannibalistic

  • secretive & nocturnal

  • greater diversity in development, respiration, and reproduction than any other vertebrate group

  • nearly all salamander larvae have external gills

    • reabsorbed later

    • Sirenidae keeps external gills (paedomorphic)

• habitat & distribution

  • common throughout U.S.

    • 70% of ~400 spp. of salamander found worldwide are located in Central & NA

  • mostly found in moist woodland habitats

    • hardwood & coniferous forests, grasslands, lowland floodplains

  • highly dependent on precipitation, temperature, & vegetation type

  • Four-toed Salamander requires sphagnum bogs

  • 22 spp. & 2 hybrid forms of the unisexual complex group are found in IN

  • some spp (Wester Lesser Siren) spend summers in estivation by encapsulating themselves in a mucous-lined cocoon

  • some permanently aquatic (ponds, lakes, & streams)

  • some terrestrial (under logs, leaf litter, rocks)

• reproduction

  • ephemeral wetlands

  • breeding season: late winter--early spring

    • few breed in fall

  • courtship practices

    • nudging

    • tail & chin tapping

    • tail fanning

  • majority of salamanders have internal fertilization

    • male salamanders deposit sperm packets (spermatophore) which the females pick up with their cloaca

    • eggs are fertilized as they travel through the oviduct and encounter spermatophore

  • majority of salamander spp. are oviparous (lay unshelled eggs)

    • all IN salamanders are oviparous

    • some give birth to gilled larvae (larviparous)

    • others give birth to fully transformed young (pueriparity)

  • eggs prone to desiccation/drying out

    • must lay eggs either in moist soil or in water

  • most do not provide parental care

    • many do guard eggs

• diet

  • carnivorous; mostly insects, spiders, & earthworms

    • occasional cannablism

Salamander Family Phylogeny

• 10 recognized families

  • 60 genera

  • 400 spp.

• Sirenidae <3 & Cryptobranchidae most primitive

• Polytomy

  • Proteidae

  • Amphiumidae

  • Plethodontidae

  • Rhyacotritonidae

  • ALL RELATED; UNKNOWN WHICH IS MORE DERIVED OR PRIMITIVE

• Salamandridae, Dicamptodontidae, & Ambystomatidae

  • most derived (especially Ambystomatidae)

Sirenidae (“Sirens”) <3

• 100 million years old--oldest extand Salamander families

• 4 spp. & 2 genera

• characteristics

  • eel-like bodies & front limbs

  • has forelimbs; NO HIND LIMBS

  • paedomorphic

    • retain larval characteristics as adults

    • external gills

  • lack eyelids, premaxillary teeth, & hind limbs

  • nocturnal

• distribution

  • fully aquatic

  • heavily vegetated, slow moving water

    • shallow water, swamps, ditches, ponds, etc.

  • found primarily in southeastern NA (not really common in IN)

• reproduction

  • breeding season: early spring

  • 200-700 eggs deposited to base of aquatic vegetation

  • may have external fertilization

• special concern; may eventually become endangered :(

Cryptobranchidae (“giant salamanders”)

• 3 spp. & 2 genera

  • Eastern Hellbender (smallest)

    • found only in northeastern USA

  • Japanese Giant Salamander

  • Chinese Giant Salamander (largest)

    • 1.5m & ~100 lbs

• characteristics

  • paedomorphic

  • flattened body & head

  • skin folds for respiration

• distribution

  • fully aquatic

    • cold, fast moving streams

  • cool shallow areas where rocks not embedded in substrate

  • essentially nocturnal

• diet

  • primary: crawfish

  • fish, aquatic insects

• reproduction

  • external fertilization

  • multiple females may lay eggs in one male’s nest (which are defended)

  • male fertilizes eggs; chases away female

  • eggs hatch in ~55-75 days

  • young remain in larval stage for 2 years

  • juveniles require an additional 3-4 years to reach sexual maturity

Proteidae (“mudpuppies”)

• 6 spp. & 2 genera

• characteristics

  • similar to sirens, but have hind limbs

  • large, bushy external gills (paedomorphic)

  • caudal fins

  • 4 toes

• diet

  • insects & fish

• distribution

  • fully aquatic

    • lakes, ponds, rivers, & streams

  • rarely seen in depths less than 1 meter

    • commonly found 20 meters below surface

  • found in central & eastern USA, southern Europe

• reproduction

  • internal fertilization

  • males & females guard eggs

• why “mudpuppy?”

  • stems from the erroneous belief that members of this family smit barking sounds when disturbed

• special concern; may become endangered

Ambystomatidae (“mole salamanders”)

• 30 spp.

• characteristics

  • stout bodies

  • thick, robust limbs

  • thick tails

  • short, blunt head

  • functional lungs

• reproduction

  • breeding season: spring

    1. males & females migrate in the hundreds to ephemeral ponds

    2. lay eggs in water

    3. stay in aquatic salamander larvae form for 4-6 months

    4. metamorphose (indirect development)

    5. leave aquatic environment

    6. spend life on land

• why “mole salamanders?”

  • comes from their habit of staying underground & in burrows of other creatures except when breeding

Plethodontidae (“lungless salamanders”)

• 2/3 of all salamander spp. belong here

• characteristics

  • primarily breathe through moist skin

  • thin, elongated bodies

  • prominent coastal grooves

  • ONLY family with nasolabial groove

  • autotomize tail when attacked

• distribution

  • diverse habitats

    • fully/semi/not aquatic

• reproduction

  • internal fertilization

    • eggs hatch into mini adults (direct development)

• diet

  • typically feed at night

  • insects, millipedes, worms, spiders, snails, & mites

Salamandridae (“newts”)

• characteristics

  • thick, granular skin

    • granules due to numerous toxic glands

    • aposematic

      • bright coloration usually to deter predators

  • unken reflex

    • posturing areas laden with high toxicity

    • tetrodotoxin

      • neurotoxin used for chemical defense

• distribution

  • live in forests

• reproduction

  1. lay eggs in water

  2. eggs --> gilled larvae

  3. partial transformation into red efts (2-3 years)

     1. really bright skin

     2. only terrestrial stage of newt

     3. only found in this family

  4. reach sexual maturity and spend life in water

• distribution

  • found in eastern & western NA, Europe, Africa, & Asia

• diet

  • eat invertebrates, amphibian, & fish eggs

Anuran Diversity (Anura = “without tail”)

• currently 45 recognized families

• ~5,500 spp.

• constantly changing taxonomy

  • spp. discoveries

  • genetic technologies

• FROGS ARE LEAPERS; TOADS ARE HOPPERS

• found on all continents except Antarctica

• reproduction

  • metamorphose (indirect development)

    • only 4 spp. have tails as adults

    • usually external fertilization

• diet

  • tadpole: herbivorous

  • adults: carnivorous

Scaphiopodidae (“Nearctic Spadefoot Toads”)

• characteristics

  • circular/sickle-shaped hardened keratinous structure on hindfoot, forming a spade

  • transitional spp.; somewhat warty and smooth

  • vertical pupils

  • don’t have prominent paratid glands

    • glands that secrete toxic substance

• distribution

  • found on tropical forest floors

  • NA, Europe, Asia, Africa

• reproduction

  • breed in temporary ponds; highly accelerated development

• diet

  • eat many insects

• special concern

Hylidae (“Treefrogs”)

• 800 spp. & 45 genera

• characteristics

  • smooth & somewhat warty

  • mostly well camouflaged (has flash colors though)

  • can have large or small toepads depending on habitat

• distribution

  • most boreal, some aquatic or fossorial

  • NA, SA, Europe, Asia, Australia

• reproduction

  • all return to water to breed

  • external fertilization

• diet

  • carnivorous insectivores

Bufonidae (“Toads”)

• ~500 spp.

• characteristics

  • thick, granular, warty skin

  • Bidder’s organ

    • vestigal ovary on larval testes

  • prominent parotid gland that secretes toxic substance

  • diurnal during spring & fall; mostly active at night in hot & humid weather

• distribution

  • most are terrestrial or fossorial

• reproduction

  • all return to water to breed

  • external fertilization

Ranidae (“True frogs”)

• ~300 spp.

• characteristics

  • slim-waisted with long legs, smooth skin, & prominent tympanums

  • dorsal lateral skin folds on back or around tympanum

  • extensive hind feet webbing

  • aquatic & nocturnal

    • some fossorial, arboreal, or terrestrial

• reproduction

  1. eggs deposited in shallow pond or creek

  2. tadpoles

  3. froglets

  4. frogs

• diet

  • tadpoles: herbivorous

  • juveniles & adults: insectivorous

    • some can eat other frogs, turtles, small mammals/birds, etc.

Phylogeny of Reptiles

• diverged from amphibians in Carboniferous era, Permian period (arid transition)

• better fossil record

• focus on

  • synapsids (archosaurians)

  • diapsids (archosaurians, lepidosaurs)

  • anapsids

Synapsids (“archosaurians”)

• branched early on from amphibian line

• completely terrestrial

• shelled & amniotic egg

• modern day mammal

Diapsids (“archosaurians, lepidosaurs”)

• archosaurs

  • gave rise to modern birds & crocodilians

  • largely responsible for dinos

• lepidosaurs

  • modern snakes & lizards (Jurassic)

Anapsids (“turtles”)

• Triassic

  • basic body plan (stayed the same for millions of years)

  • Odontochelys

    • late Triassic (220 MYA)

    • discovered in 2008, predates Proganochelys by 10M years

    • “toothed shell”

    • found in E. Asia, shallow marine waters near shore

  • Proganochelys

    • late Triassic (210 MYA)

    • most well-known

    • “early turtle”

    • 3ft, 75 lbs

    • possess few teeth

      • modern turtles lack teeth entirely

• Jurassic

  • Eileanchelys

    • late Jurassic (165-160 MYA)

    • found in W. Europe (Scotland)

    • earliest pond turtle

    • discovered in 2008

• Cretaceous

  • Archelon (marine turtles <3)

    • late Cretaceous (75-65 MYA)

    • found in oceans of NA

    • “Ruling Turtle”; 12 ft, 2 tons

    • large, flipper-like arms & legs

    • closest living relative: leatherback

Early Reptiles: Amniotes

• Casineria: Early Carbnoiferous (340 MYA)

  • salamander-like early tetrapod

  • 5 digits with claws

  • 1st amniote

• amniotes

  • eggs survive out of water

  • disperse onto drier land

1st Lizards, Hylonomus

• Carboniferous (315 MYA)

• discovered in Canada

• characteristics

  • earliest known reptile

  • among first amniotes, anapsid

  • small, lizard-like (8-12 in)

  • fossil with distinct toe & scales

  • numerous sharp teeth (insectivores)

Mesozoic (“Age of Reptiles”)

• explosive radiation of reptiles

  • most numerous & largest

• dominant terrestrial & aerial animals

  • formidable marine predators

Archosauromorphs

• “Ruling Reptiles” of Mesozoic

  • early diapsid amniotes

• ancestral to crocodilians, birds, & turtles

Crocodilians

• surviving archosaurs

• early ancestors (Jurassic-mid Cretaceous)

• Stomatosuchus

  • ~36 ft

  • swamps, N. Africa

• Sarcosuchus

  • “flesh crocodile”

  • ~40 ft

  • “Super Croc”

Lepidosauromorphs

• 2nd major Diapsid lineage

  • ancestral to squamates (lizards, snakes), tuataras

• first appeared late Permian

Tuatara (Sphenodontia)

• living fossils; Triassic

  • extant; New Zealand

• descended from beak-headed reptiles (Rhinocephalia)

Order Testudines (or Chelonia), Turtles

• shells helped them persist for 200 MYS

• 400 spp.

• distribution

  • aquatic, semi-aquatic, terrestrial

• reproduction

  • oviparous (all lay eggs)

• diet

  • most adults are omnivorous; some completely herbivorous/carnivorous

  • all turles lack teeth,

• distribution

  • tropic & temperate

Testudines, Chelydridae (“snapping turtles”)

• 2 genera; Macroclemys & Chelydra

  • each with 1 spp.

• characteristics

  • large, long tails

  • muscular legs

  • massive head

  • greatly reduced plastrons

  • nocturnal, fully aquatic

    • eggs on land

• distribution

  • NA, SA, SEA

Testudines, Kinosternidae (“mud & musk turtles”)

• 4 genera, 23 spp.

• characteristics

  • <6 in

  • glands on side produce musky odor

  • domed carapace & plastron (hinged)

• distribution

  • semi-terrestrial

  • poor swimmers; walks along bottom of streams & ponds

  • prefer sandy or muddy dwellings

• reproduction

  • lay several small clutches throughout year (4-5/clutch)

  • all but one spp. in IN have TDS (temperature dependent sex)

    • warm = male (depending on spp.)

• diet

  • omnivorous, but prefer insects, tadpoles, & fish

Testudines, Emydidae (“basking, marsh, & box turtles”)

• 42 spp.

• relatively long-lived

  • eastern box turtle can live up to 80-100+ years

• distribution

  • aquatic, semi-aquatic, some terrestrial

• low reproductive rates

  • countered by longevity

• diet

  • adult: omnivorous; some herbivorous

  • juvenlie: carnivorous

Testudines, Trionychidae (“soft-shelled turtles”)

• GENETIC SEX DETERMINATION; NOT TSD

• characteristics

  • long, tubular nose

  • fully webbed feet (good swimmers)

• distribution

  • almost fully aquatic

    • pharyngeal respiration

      • special throat lining that absorbs O2 from water

• reproduction

  • females lay clutches along sand bars/gravel banks

Ectothermy: Amphibians & Reptiles

• primary heat source external

• heat not always available (winter)

• more economical (behavioural changes to be warm)

Endothermic: Birds & Mammals

• primary heat source internal

• better in cold environments

  • more range than ectothermy

• more expensive

Thermal Interactions & Heat Exchange in Ectotherms

• heat exchange with environment occurs via

  • radiation

  • convection (smaller = faster temp change)

  • conduction (smaller = faster temp change)

  • color also a factor (dark absorbs more heat)

Body Temp Trends

• max & min voluntary can be highly variable

• tropical mean temps is higher than temp

• snakes & lizards tend to have highest body temps

• warmest to coolest

  1. lizards

  2. snakes

  3. turtles

  4. frogs

  5. salamanders

Temp Ranges & Tolerances

• Active Body Temperature (ATR) varies depending on

  • taxa

  • habitat

  • season

  • genetics

• for most, range is between 27C -- 35C

  • few reptiles have ATRs <20C

Regulation of Body Temps

• due largely to behavioural changes (change posture/position, etc.)

• amphibians (terrestrial) handle regulation differently because of moist skin

  • low resistance to water loss

• Tb (body temp) largely tracks Te (environment temp)

  • couple of degrees cooler due to evaporation

• reptiles can be exposed to sun without excessive water loss (scales)

Dormancy

• response to temp extremes & environmental cues

• can occur in 3 different forms

  1. hibernation

  2. freeze tolerance

  3. estivation

• Scaphiopus: active 1 month/year in Arizona

• Thamnophis: active 4 months/year in Manitoba

• dormancy forms explained

  1. hibernation

     1. Tb largely allowed to track Te, except that metabolic activities slowed even more than “normal” for a given temp

     2. animals tend to move during hibernation (brumation)

     3. aquatic hibernators sink to bottom

  2. freezing tolerance

     1. ice crystals destroy cells & extracellular fluid freezes & dehydrates cells

     2. few spp. can do this (Pseudacris crucifer <3)

        1. use cryoprotectants (glycerol or glucose); replace water in cells with antifreeze

  3. estivation

     1. animals inhabiting desert & semidesert environments

     2. physiology not well-known

     3. animals flee to deep burrows with high humidity & moist soils & reduce their metabolisms

     eastern spadefoot, Scaphiopodidae

Order Squamata (“Lizards”) [snakes will start later]

• 8,000 spp.; 5,000 are lizard spp.

• most abundant & diverse reptilian group that exists today

• lizards will autotomize (lose) tails as defense mechanism

• reproduction

  • extremely diverse, but all have internal fertilization

  • some oviparous (lay eggs outside of body)

  • some viviparous (live birth)

  • some ovoviparous (eggs hatched within body)

  • some have significant courtships (lizards)

  • lay flexible or hard eggs

  • little parental care

• diet

  • carnivorous

• distribution

  • occur in all tropical & temperate regions

Phrynosomatidae (“spiny lizards”)

• 125 spp.

• many morphological differences

• distribution

  • Sceloporus: arboreal, terrestrial, rock-dwelling

• reproduction

  • most oviparous

  • some viviparous

Anguidae (“glass or alligator lizards”) LEGLESS

• 120 spp.

• characteristics

  • has all characteristics of lizard (moveable eyelids, external ear)

  • long & have shiny scales underlined with bony plates (osteoderms)

  • autotomize their tails (which are ~2/3--3/4 of whole body)

  • highly terrestrial & semi-fossorial

• reproduction

  • mostly oviparous

  • some ovoviviparous

  • few viviparous

• diet

  • carniverous

• distribution

  • NA, SA, Europe, Asia

Teridae (“whiptails & racerunners”)

• 110 spp

• characteristics

  • long, slender bodies with well-developed limbs & very long tail

  • often have yellow stripes on body

  • males have blue/green chest during breeding

• distribution

  • only found in NA & SA

  • terrestrial; sandy prairie

• reproduction

  • oviparous

  • some spp. are parthenogenic

    • populations are all female, so all eggs laid are unfertilized & clones of the mother

    • six-lined racerunner is NOT PARTHENOGENIC

Scincidae (“skinks”)

• largest of all lizard families (1200 spp.)

• characteristics

  • osteoderms give them stiff & shiny bodies

  • autotomize tails

• distribution

  • highly varied

    • terrestrial, semi-fossorial, diurnal, etc.

  • everywhere except Antarctica

• reproduction

  • oviparous, ovoviviparous, viviparous

• diet

  • insectivorous

Order Squamata (“snakes”)

• 3000 spp.

• characteristics

  • immovable eyelids

  • legless

  • no external ears

  • Jacobson’s organ (tongue-flicking)

  • left lung either entirely absent or highly degenerate

• distribution

  • highly varied habitats (terrestrial, arboreal, etc.)

• reproduction

  • mostly oviparous, but can be other two

Viperidae (“vipers”)

• 215 spp.

• characteristics

  • long hinged fangs with a hemotoxin (swelling & hemorraging)

    • cobras have a neurotoxin (central nervous system)

  • broad heads & stocky bodies

  • Loreal pit organ senses heat

• habitat

  • terrestrial with wide variety of habitats

  • NA, SA, Europe, Africa, Asia

• reproduction

  • viviparous

• diet

  • carniverous

Colubridae (“snakes”)

• was 2000, but now 650 spp.

• characteristics

  • can be 7in -- 12ft

• distribution

  • terrestrial & aquatic

• reproduction

  • oviparous

  • ovoviviparous

Natricidae (“snakes”)

• 200 spp.

• distribution

  • mostly tied to aquatic environments

• reproduction

  • viviparous

  • ovoviviparous

• diet

  • carnivorous

Dipsadidae (“snakes”)

• 700 spp.

• characteristics

  • small-medium

  • from New World

• distribution

  • secretive; hides under cover

• reproduction

  • oviparous

• diet

  • diverse (invertebrates, amphibians, etc.)

Reproduction & Life Histories

• fertilization can happen inside/outside of female

• development can be direct/indirect

Gametogenesis & Ovulation

• most amphibians, 2 sexes required

• reproductive timing has internal controls

  • ultimately coordinated by environment (temp & photoperiod change)

• Gametogensis

  • division & growth of gametes within ovaries & testes through hormonal activation

• Vitellogensis

  • accumulation of nutrients in cytoplasm of developing egg

  • rapid growth of oocytes (egg 10-100x size)

• Ovulation

  • occurs when follicular & ovarian walls rupture

  • releases ova into oviduct

    • as eggs pass through oviduct, protective membrane are deposited around them

      • number of layers is spp. specific

  • amphibian eggs are anamniotic

  • eggs expelled in gelatinous masses or strings

Fertilization

• penetration of sperm & fusion of male & female pronuclei

• many sperm can reach the egg, but only one will penetrate it

  • salamanders have polyspermic fertilization

  • sperm heads (acrosomes) digest eggs membranes, making tiny hole

    • sperm pronuclei moves into ova cytoplasm; fusion

• 2 types

  1. external

     1. normal for Sirenidae & Cryptobranchidae, and most Anurans

  2. internal

     1. found in other salamander families

• external

  • simultaneous shedding of eggs & sperm into water

  • constrain where eggs are laid

  • frogs: males grasp female in amplexus so their cloacas align

  • salamanders: either amplexus or male follows female to deposit

  • inguinal amplexus

    • male has front legs around female’s upper waist (under arms)

  • cephalic amplexus

    • male’s hind legs wraps around female’s head

• internal

  • few frog spp. (Pacific NW), Salamandroidea salamanders, all caecilians

  • allows eggs to be laid in spot & time of choice

  • frogs: hemipenis delivers sperm to female cloaca

  • salamander: spermatophores deposited externally

    • proteinaceous pedicel capped by sperm packet

  • spermatheca

    • sperm storage in series of tubules on cloaca’s roof

Reproduction without Fertilization

• asexual reproduction

  • without male contributions

    • 100% female populations in some taxa

  • 2 types

    1. Hybridogenesis: progeny only transmits female chromosome; all female populations

    2. Gynogenesis: diploid/triploid egg only activated by sperm; no male chromosomes incorproated into embry

       1. only female offspring

       2. fathers from 5 specific spp.

          1. Jefferson salamander, blue spotted salamander, tiger salamander, smallmouth salamander, streamside salamander

Gynogenesis

• “unisexual” hybrid Ambystoma complex

• 5 MYA

• ploidy # varies

• 17 different combos

  • e.g. 2n, 3n, 4n, 5n (n = copies of genetic contribution)

    • if 4n with 4 blue spotted salamander & 1 Jefferson, will look more like blue spotted

Parental Care

• any form of post-egg laying parental behaviour that increases offspring survival at some expense of parent

• most amphibs show no parental care aside from nest construction

• represented by a variety of behaviours

  1. nest, egg, or young attendance/guarding

  2. egg brooding

  3. egg, larval, or hatchling transport

  4. feeding of young

Development

• Exotrophic

  • limited amount of yolk; allows females to lay more, but smaller eggs (quantity > quality)

  • larvae hatch quickly, but must feed themselves

• Metamorphosis

  • shift from embryonic & larval stage to mature terrestrial stage

  • initiated hormonally, but environment also plays a role (crowding, predation, food availability, etc.)

• Paedomorphosis

  • retention of juvenile characteristics as adults

  • two types

    1. progenesis: accelerated sexual maturity relative to stomatic growth

    2. neoteny: slowing of stomatic growth with onset to sexual maturity

Growth

• addition of enw tissue in excess oif what was lost in damaged tissue

• two types

  1. embryonic

     1. increase when high quality food is in abundance

     2. influenced by temp (higher = faster development; not too extreme though)

  2. juvenile

     1. much slower because of unpredictable food & environment

• GROWTH IN AMPHIBIANS IS INDETERMINATE/NEVER-ENDING

Age

• intervals (periodicity & not age) are important

  1. sexual maturity (4 months -- 7 years)

  2. Embryogenesis (can be truncated in Scaphiopodidae)

  3. larval period → metamorphosis

Dynamics of Reptilian Reproduction

• multitude of patterns geared to the right environment for offspring

• all temperate spp. are cyclic

• tropical spp. cyclic or acyclic

• 2 patterns (temperate salamanders)

  • winter/spring mating & egg disposition (Ambystomatids)

  • late summer/fall mating & spring egg disposition (Plethodontids)

• mate attraction & selection

  • location usually not a problem

  • reproduction more efficient within home range (sometimes movement is necessary)

  • courtship is key

  • female-heavy investment in gametes = most fit mate

Reproduction & Life Histories of Reptiles

• major difference in reptilian reproduction compared to amphibians

  • all have internal fertilization

  • direct development

  • amniotic egg

    • development can occur on much drier land

Gametogenesis & Ovulation

• Vitellogenesis very important in egg-laying vertebrates

  • accumulation of nutrients → yolk

• vitellogenin selectively absorbed by oocytes & enzymatically converted to yolk proteins (pinocytosis)

Cleidoic (shelled) egg

• prevents desiccation & contamination by environmental pathogens

• creates own aquatic environment

• by folding & curling, reptile embryo can be very long

• 3 extraembryonic membranes are formed (no need to know function)

  1. Allantois

  2. Chorion

  3. Amnion

Fertilization & Copulation

• copulatory organs

  • turtle & crocodilians: a penis of spongy connective tissue erects & retracts via vascular pressure (similar to mammals)

  • tuataras don’t have copulatory organs

  • squamates: penis lost & later replaced by hemipenis

• sperm storage

  • delayed fertilization → females can mate with more than one male → multiple progeny

  • sperm storage tubules on upper-mid section of oviducts

  • mechanism for expelling sperm from these tubules is unknown

Reproduction without Fertilization (reptiles)

• Asexual

  • 1 type in reptiles

    1. parthenogenesis

       1. females reproduce without sperm

       2. inheritance is clonal

Parental Care

1. pre-depositional

   1. involves quantity & size of egg components (egg components = eggshell, protein, lipids, yolk [oviparous reptiles])

   2. hatchling turtles & crocodilians have 50-70% more lipids than required

2. post-depositional

   1. selection of best sites

3. live-bearing

   1. 20% of all lizards & snakes

   2. ovoviviparous

      1. holds eggs much longer than oviparous spp.

      2. embryos can be supported entirely by egg yolk

      3. embryos can absorb some nutrients through oviducts

   3. viviparous

      1. placenta-like structure transfers nutrients to developing embryo

Embryo Development

• direct development in all reptiles

• clutch & egg size msy be proportional to body size

  • larger female = larger eggs & clutch

• reptilians that develop from terrestrial egg

  • humidity (more important for leather eggs)

  • temperature (ATR)

• temperature-dependent sex determination (TSD)

  • widespread in reptiles

    • found in all crocodilians, tuataras, & 11 spp. of turtles & squamates

  • average temp during 2nd trimester

    • crocs & lizards: male at high temps

    • turtles: females at high temps

Growth

• 2 growth pulses

  1. embryonic

     1. increases when yolk is available & decreases with lower Te

  2. juvenile

     1. much slower due to unpredictable food & environment

Age

• similar to amphibians (periodicity > age)

  • conception → hatcling/birth

  • sexual maturity

  • reproductive senility

• reproductive periodicity very important

• longevity can be great for some reptiles

Dynamics of Reproduction

• mate attraction & selection

  • most fit male >>>

  • territory more important because of reduced need to breed

  • courtship:

    • visual signals are important, but also tactile & chemosensory receptors involved

Introduction

• each population will adapt differently and will eventually diverge genetically (evolve) from other populations

  • if divergence continues, speciation would occur (rare outcome)

• the rate of gene flow is a function of the closeness of the populations and the dispersal tendency of the species

Classification

Species

• Today distinguishes by differences in:

  • body function

  • biochemistry

  • behaviour

  • genetic makeup

• Classical Biological Concept Definition:

  • genetically distinctive populations of individuals isolated reproductively from all other populations

Alternative species concepts

• 27-30 concepts

• Ecological species

  • defined in terms of its ecological niche

• Morphological species

  • defined by morphology (structure)

• Genealogical species

  • defined as a set of organisms with a common and unique genetic history as shown by molecular patterns

Subspecies

• Def 1:

  • Taxonomic subdivision of a species

• Def 2:

  • A population of a particular region genetically distinguishable from other populations and capable of interbreeding with them

• Def 3:

  • A grouping of organisms that differ from other members of their species by color, size, or various morphological features

Cline

• A gradual and continual change in a character by a series of populations or throughout the range of a species

• Usually along a geographic or environmental gradient

  • Individuals at the two extremes differ

• Clinal Variation

  • 

• Clinal Variation in plastral markings of painted turtles

  • Western forms -- intricate

    • 

  • Hybrid -- intermediate

    • 

  • Midwestern/Midland -- single

    • 

• “Ring species”

  • Individuals that don’t interbreed but all stem from one population

    • 

    • Lungless salamander (Ensatina eschscholtzi)

Morphological Variation

• Latitudinal changes within a species

  • Changes in body weight; Bergman’s rule

    • Animals have a tendency to be larger in polar regions, medium in temperate climates, and smallest in tropical ones

    • DOES NOT ALWAYS APPLY TO REPTILES & AMPHIBIANS

  • Changes in body color

Biogeography

• 3 major factors influence geographic distributions of amphibians & reptiles

  1. Climate

     1. Amphibians have 3 factors in regards to climate

        1. Temperature

        2. Rainfall

        3. Periodicity

  2. Availability & access to resources

  3. Dispersal abilities

     1. Small fossorial amphibians & reptiles have poorer dispersal abilities

     2. Large aquatic animals tend to be better dispersers

Movements

Daily Movements

• Feeding

• Thermoregulation

• Predator avoidance

Seasonal Movements

• Generally more extensive but still generally considered to be <0.5 km

• Breeding

  • Amphibians generally go towards water

  • Reptiles generally go towards land

• Hibernation

  • Snakes searching for hibernacula to escape the cold

• Habitat Utilization

  • Largely associated with change in food availability or habitat quality

Dispersal

• Movement outward from home area; often implies colonization

• Important for maintaining gene flow in a population

• Infers some genetic exchange (if those dispersing individuals successfully reproduce)

• Undirected movement to locations unknown by the dispersing animals

• Costs & benefits

  • Benefits

    • May reduce intra-specific competition

    • Likely to come into contact with different individuals unrelated to you (minimizes inbreeding)

  • Costs

    • Resources could be lacking

    • Increased predation risk

Orientation & Navigation

• Piloting

  • Simplest form; ability to recognize landmarks

  • Possessed by all reptiles & amphibians

• Compass orientation

  • Sense of direction

  • Independent of local cues (i.e. basking/perching sites)

• True navigation

  • Ability to orient & move toward a location; an internal map

• Others

  • Visual orientation (polarized light)

  • Pineal organ (salamanders)

  • Parietal eye (dictates photoperiod)

  • Olfaction

  • Celestial (stars & celestial bodies)

Orientation in baby Loggerhead Turtles (Chelonia mydas)

• Visual cues

  • Uses stars & moon to help hatchlings find ocean

• Wave Orientation

  • Takes them out into the ocean

• Magnetic Orientation

Home Range

• 

• 

• Home range varies between the sexes

  • larger in males, smaller in females

  • male home range size 2x amount of female and is increasing

• Defense (Territoriality)

  • Usually very expensive, but where a required resource is insufficient for all individuals, defense may have evolutionary advantage

  • Types

    1. Territorial defense

       1. Relatively rare

       2. Mark territory with pheromones

       3. Accomplished through direct combat

    2. Site defense

       1. More common

       2. Defense of point resource

       3. Basking sites, food, nesting

Introduction to Feeding & Food Habits

• Although some exceptions exist, amphibians and reptiles mostly feed on:

  • Frogs & salamanders: insects

  • Turtles: plans & animals (vertebrates & invertebrates)

  • Squamates: animals (vertebrates & invertebrates)

Projectile Tongues

• Commonly found in amphibians (Anurans)

• 

  • On left:

    • A: projection; mouth opening

    • B: tongue flips forward

    • C: tongue fully extended and turned upside down; dorsal surface of tongue tip encircles prey

    • D: muscles contract and the retract tongue back inside

• Plethodontidae Salamanders

• 

  • A: minimal protrusion

  • B: Modest protrusion

  • C: free tongue and considerable protrusion

  • D: free tongue and extreme protrusion

  • In some salamander spp., length of tongue = half length of body

• Squamates (Chameleons)

• 

Digestive System

Digestive Glands

• Oral cavity

  • Amphibians: Intermaxillary gland

    • Secretes a sticky compound that helps prey adhere to the tip of the tongue

    • Found in both frogs & salamanders

  • Reptiles: venom glands

    • Modified salivary glands

    • Very well-developed

    • Used to subdue and digest

• Opisthoglyph

  • 

  • Rear-fanged snakes (back of maxilla)

  • Fangs not hollow

  • Weak venom

  • Due to location of fangs, snake must move prey to back of mouth before digestion

  • IN: Hognose Snake

• Proteroglyph elapid snakes

  • 

  • Forward-grooved snakes

  • Shortened maxillary bearing fangs with few teeth except for enlarged fangs

  • Fixed fangs with a hollow tube (like a needle/syringe)

  • Many species are some of the most toxic (neurotoxins)

  • Due to the shortened nature of its front teeth, it must hold on momentarily to inject the venom

  • Cobras & Brown Snakes (Australia)

• Solenoglyph Viperid Snakes

  • Most advanced venom delivery method system of any snake

  • Each maxilla reduced to a nub supporting a single hollow fanged tooth

  • Fangs can be as long as half the length of head

  • Gaboon Viper: 2 in long fangs

  • Folded against roof of mouth (hinged)

  • Snake opens mouth 180°

  • Slightly less toxic than proteroglyph; a hemotoxin

  Foraging Modes

  Two general foraging methods

  1. Sit-and-wait (ambush foraging)

     1. Very little investment in time & energy searching for prey

     2. Most energy spent in capturing & handling prey

     3. Users generally have very good eyesight or special organs (pits organ)

     4. Users rely on cryptic coloration

  2. Active foraging (wide foraging)

     1. Predators are moving through the environment in search of prey

     2. Combination of visual & chemical cues

     3. Larger home range

     4. Higher ATR

  3. Likely a continuum of foraging modes from these two extremes

• 

  • Numerous ecological, behavioural, physiological, and life history parameters that correlate with foraging modes

Factors influencing foraging behaviour

• External factors

  1. Prey availability

  2. Predation risk

  3. Societal interactions

  4. Habitat structure

• Internal factors

  1. How hungry is it?

  2. Amount of learned experiences (coupled with age)

  3. Sex and reproductive state

     1. Males may not forage since they are protecting their territory; females may forage more to produce enough eggs

  4. Genetics

• Phylogenetic factors

  1. Sensory limitations

  2. Morphological characteristics

  3. Physiological constraints

Prey Detection

• Amphibians and reptiles can detect prey using different cues

  • Visual

    • Mostly used by sit-and-wait predators

    • Large, well-developed eyes

    • Discriminate prey based on shape and size

    • Binocular perception

      • Can detect depth & distance

    • Most align heads or entire body axis with that of prey before attacking

  • Chemical

    • Olfaction

      • Prey location identification by sniffing or rapid bugle pumping (frogs inflating their lower mouth)

      • Long-distance detection system

      • Main feeding sense of salamanders & lizards

    • Vomerolfaction (Jacob’s organ)

      • Sensitive to high molecular weight compounds

      • Transported to oral and nasal cavities by the snout or tongue

      • Short-range detection system

      • Main feeding sense in some salamanders & most snakes

        • Snakes have bifurcated tongues (provides directionality of info)

      • 

      1. Tongue flicks and picks up high molecular weight compounds

      2. Snake retracts tongue into set of grooves in upper snout in maxilla

      3. Forks transfer compounds into epithelial cells in Jacobson’s Organ

    • Taste

      • Help distinguish food items from non-food items

  • Tactile

    • Relatively poorly understood

    • Mechanoreceptors in the skin (lateral line in aquatic amphibians)

    • In several spp., flaps of skin are highly innervated and also help in the tactile detection of prey

  • Thermal

    • Infrared light sensed by nerve endings in skin of head which are located inside pit organs

      • Loreal pits in vipers

      • Nasal/upper labial pits in pythons and boas

    • Pits open anteriorly (always face forward) and provide a binocular

    • Most effective for nocturnal spp. that feed on mammals & birds

• Many spp. use some combination of these cues

Prey Capture & Ingestion

Prey Capture

• Biting and grasping

  • Prey typically swallowed whole

• Constriction

  • Common in boas & pythons

• Injected venoms

  • Hemotoxins, neurotoxins

• Filter feeding

  • Tadpoles: large buccopharyngeal cavities

• Suction feeding

  • Prey is vacuumed into mouth

• Projectile tongues

Food Habits

• Specific food habits depend on:

  1. Feeding adaptations of animal

  2. Size of animal and prey-capturing methods

  3. Habitat

  4. Relative abundance and size of prey available at time of feeding

Communication: Types

• Social behaviour

  • An interaction with one or more conspecifics and occasionally with individuals of different species as well

• Communication

  • Transfer of information from a signaler to a receiver

• 4 basic types

  • Visual

    • Distinct colors/body movement

  • Acoustic

    • Vocalization/rubbing body parts together

  • Chemical

    • Odors

    • Well-developed in salamanders, lizards, and some snakes

  • Tactile

    • Individual rubs/presses/hits a body part against another individual

• Advantages for communication

  • Identify & locate mates in a complex environment

Communication: Salamanders

• Chemical cues

  • Salamanders use pheromones

  • Hormones are produced by courtship glands

• Tactical cues

  • Mate location in Plethodontid salamanders aided by nose-tapping

  • Also bite, slap, or rub part of their bodies against each other

• 

• 

• 

• 

Communication: Frogs

• Acoustic cues

  • Very important

• 4 basic call categories

  1. Advertisement

     1. Attract mates

     2. Deeper = better

  2. Reciprocation

     1. Very rare

     2. Female calls in response to male

  3. Release

     1. Males amplexing other males, so a release call is made by the one being amplexed

  4. Distress

     1. Grasped by predator

• Frogs can make vocalizations by passing air back and forth between lungs, vocal cords, and vocal sacs

• 

• Visual cues

  • Bright colorations

  • Mostly in diurnal spp.

Communication: Turtles

• Visual cues

  • Headbobs

• Tactile cues

  • Ram, flip, trailing, biting, tickling

• Chemical cues

  • Special glands on bridge of shells

  • Cloacal secretions may also play a role

Communication: Lizards

• Visual cues

  • Coloration of dewlaps, heads and sides of the body in males and bright coloration in females

  • 

  • 

  • 

• Chemical cues

  • Pheromones (skinks)

• Tactile cues

  • Tongue flicking

  • Neck & body scratching

Communication: Snakes

• Tactile signals very important for snake courtship

• 3 different phases

  1. Tactile phase

     1. A lot of chemosensory sampling of males to determine sex of the individual

  2. Male chases female to copulate

  3. Intromission & copulation

Group Behaviour: Competition

• Competition

  • Interspecific

    • Occasionally occurs among related spp.; frequently congregating spp. partition habitat temporally (especially during breeding)

      • Different spp. in ephemeral ponds organize by spp. and by time of day

  • Intraspecific

    • Occasionally occurs when resources are limited; minimized in larval/juvenile forms

Group Behaviour: Cooperation

• 2 forms

  1. Hibernation

     1. Different spp. of snakes hibernating together to reduce evaporative loss during winter

  2. Breeding Aggregations

     1. Male frogs taking turns to call a female (reduces intraspecific competition)

Introduction: Predation

• The greatest cause of mortality in natural amphibian and reptile populations

• Any traits that reduce predation are under strong selection pressure

• Most amphibs and reptiles employ several different mechanisms

Predator Avoidance

1. Escaping detection

   1. Not being present when a predator i searching for prey

2. Crypsis and immobility

   1. Resemble a random sample of certain aspects of the enviro

   2. Polymorphic coloration

      1. individuals in a species have different colors and patterns

3. Aposematic coloration

   1. Bright coloration in animals that produce noxious or lethal chemicals from skin glands

4. Postural warning

   1. Assuming several defensive postures to “scare” predators

   2. Red-eyed tree frog

5. Mimicry

   1. Batesian

      1. When a nontoxic species mimics a toxic or protected one

   2. Mullerian

      1. When one or more potentially dangerous species resemble each other and each is both the model and the mimic

   3. Northern coral snake being imitated by the scarlet snake

      1. “Red on black, friend of Jack. Red on yellow, kill a fellow.”

6. Escaping approach

   1. Running away and hiding

   2. Active foragers

Escaping Predators

1. Skin, armor, and spines

   1. Structures can protect an animal from a predator attack

   2. Not very developed in amphibs

2. Chemical defense

   1. Glands producing irritating, distasteful or lethal compounds

   2. Very developed in amphibs

3. Death feigning

   1. Eastern hognose snake

4. Tail displays and autotomy

   1. Tails separating from body

5. Schooling

   1. Commonly seen in tadpoles

   2. Group can appear as one big organism instead of individual tadpoles

What is a disease?

• “Any deviation from, or impairement of the normal structure or function of any part, organ, or system of the living animal or plant body”

• Clinical signs may be morphological, physiological, or behavioural

  • Morbidity, mortality, reduced growth, malnutrition, developmental, mental, activity level, appearance, etc.

Major types of diseases

• Infectious

  • Contagious v. non-contagious

• Genetic

• Nutritional & physiological

  • Scurvy

• Toxicological

  • Biotic v. non-biotic

    • Biotic: toxic algal blooms

• Traumatic

  • Losing a limb

• Mental Illness

• Combinations

Agents of infectious disease

1. Microparasites

   1. Bacteria, viruses, protists, fungi

   2. Infected v. uninfected

      1. Really the most important thing

   3. Reproduce very quickly inside host

2. Macroparasites

   1. Helminths (trematodes, nematodes, cestodes, acanthocephalans)

   2. Arthropods (ticks, copepods, lice, insects, mites, fleas, etc.) & leaches

   3. Intensity-dependent pathology

      1. The more macroparasites you have, the greater the impact they have on you

Modes of transmission

• Direct

  • Horizontal

    • Sneezing, coughing, etc.

  • Vertical

    • Parent to offspring

  • Single host

  • Multi-host

• Indirect

  • Complex life cycle

    • Needs multiple hosts

  • Vector-borne

• All parasites want to maximize transmission

Parasites and extinction

• Parasites rarely drive their hosts to extinction

  • Transmission limited at low population sizes

  • Similar to predator-prey cycles

• Several factors can help drive disease-induced extinction

  • Small populations (inbreeding, stochasticity)

  • Frequency-dependent transmission (STDs)

  • Multiple host species

    • If parasite is a generalist

  • Environmental reservoirs or persistence

Amphibian parasites

• Host to a diversity of parasites

  • Viruses

  • bacteria

  • Fungi

  • Water mold

  • Trematodes

• Most are relatively benign and the individual can clear the infection or live with it

3 Parasites of Conservation Concern

1. Batrachochytrium dendrobatidis (fungus)

2. Ranaviruses (virus)

3. Ribeiroia ondatrae (trematode)

• Linked to mortality events, severe pathology (malformations), or extinctions

• Relatively new to science (1996)

• Appear to be increasing in prevalence in amphib populations either locally or globally

Chytrid fungus

• Batrachochytrium dendrobatidis (Bd)

• Non-hyphal parasitic fungus (aquatic)

• Only chytrid species pathogenic to vertebrates

• Attacks keratinized tissue

  • Larvae: only the mouthparts have keratin

  • Adults: Keratin found throughout skin

• Life cycle

  • Zoospores

    • Floating around in water

    • Once contact is made, forms a cyst right under skin

    • Cyst continues to grow and eventually pops like a pimple

    • Goes on to infect more skin

Field signs of Bd infection

• Lethargy and paralysis

• Sloughing of skin and skin lesions

• Time to death highly variable (18-48 days)

• Infected individuals may appear healthy

• Some species live with infection

  • May serve as reservoirs for other spp. to get infected from

• Loss of pigmentation in mouth parts of larvae

Cause of Bd mortality

• Impaired osmoregulation (suspected primary cause)

  • Decreased water uptake and ion exchange (sloughed skin)

  • Altered electrolyte/solute levels (decrease in calcium interferes with muscle activity)

    • Lethargy and paralysis

• Impaired cutaneous respiration

Why is the fungus emerging?

• 2 hypotheses

  • Native pathogen

    • Increasing in prevalence due to some environmental change (climate change)

    • Increased amphib stress

  • Novel introduction

    • Pathogen somehow got introduced to a new area

    • Encountering hosts that have never evolved to deal with this pathogen

    • Africa → Central America, Australia, US

    • 

    • 

Bd Distribution

• Present in most well sampled areas

• While detected globally, the outcome of infection varies widely among regions

• 

Bd: Patterns of susceptibility

• Species vary widely in susceptibility to infection and disease outcomes

  • Extinctions have occurred

  • Frogs appear to be more susceptible than salamanders

  • Use of aquatic habitats increases chances of exposure

  • Some species act as reservoirs

Amphibian ranaviruses

• Infect ectothermic vertebrates (herps and fish)

• 6 total spp.

• 3 spp. are known to infect herps (>15 isolates)

• All 3 ranaviruses linked to amphibian die-offs

  • Ambystoma tigrinum virus (ATV)

  • Bohle iridovirus (BIV)

  • Frog virus 3 (FV3)

• Characteristics

  • dsDNA (double-stranded DNA)

  • 3x smaller than bacteria

  • Icosahedral shape (20 sides)

  • Paracrystalline arrays

Organ Destruction

• 3 primary organs: liver, spleen, and kidney

  • 

• Cell death occurs within 6-9 hrs

• 

• 

• Fast progression

  • 1-3 days signs, 3-7 days mortality

Persistence and transmission

• Concerns typically evaporate along with bodies of water

• Becomes a concern again when ponds form and adults congregate to breed

  • No vertical transmission; horizontal instead

Ranavirus: Patterns of susceptibility

• Species vary widely in susceptibility to infection and disease outcomes

  • Population declines have occurred

  • FV3 → frogs; ATV → salamanders

  • Ranids highly susceptible to FV3

    • Wood frogs, tree frogs, etc.

  • Fast developing larvae = poorer immune functions

  • Some species may act as reservoirs

Parasite Infection → Deformed Frogs (Trematoda)

• Ribeiroia ondatrae (Trematoda)

• Parasitic fluke (Plathyelminthes)

• Targets limb tissue

• 

Cycle of deformity

1. aquatic snails

   1. Picked up from infected bird feces

   2. Rediae, cercariae

   3. Asexual reproduction

2. Amphibs

   1. Metacercariae

3. Waterfowl

   1. Adults

   2. Sexual reproduction

• Extra legs serve to make predation easier (to complete parasite life cycle)

• 

Human Influences

• Factors that influence snail abundance should be linked to parasite load in amphibs and malformations

• Eutrophication

  • Ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates

  • Bottom-up effect

    • Algal (plant) population growth increases due to the addition of fertilizer

    • Higher snail abundance → more infected snails → More cercariae per infected snail → more infection in amphibians

Conservation of Amphibians and Reptiles

General Principles

• Biodiversity crisis

  • Loss and reduction in diversity at all levels (genetics → ecosystems)

  • Primarily focus on single spp. conservation due to lack of resources for anything much bigger (e.g. habitat/environment)

• Extinction

  • Rate has greatly exceeded the “normal” historical rates

  • Could lead to cascading extinction events

    • The loss of one spp. causes the loss of multiple

Current trend: Amphibians

• World-wide amphibian declines

  • 1,260 of 6,000 spp. (21%) are endangered

  • 1,856 of 6,000 spp. (32%) are threatened

  • 2,469 spp. are in decline (43%)

Current trend: Reptiles

• World-wide reptile declines

  • Reptiles not completely assessed (mostly Chelonians)

    • Best estimate 833 of 6,500 spp. (13%) endangered

  • Turtles and tortoises well reviewed

    • 108 of 257 spp. (42%) threatened

Human Impacts

• Humans have modified the environment everywhere through

  • Habitat modification, fragmentation, loss

    • Most visible human mediated environmental change

    • Agriculture

    • Urban growth and paving

    • Overall consequences:

      • Habitat alteration and fragmentation (dispersal barriers)

      • Increased mortality due to road kills

      • Loss of breeding, foraging, & over-winter areas

      • Population declines and extinction in some cases

    • Road mortality

      • Skewed sex ratios in turtle populations

        • Predicted higher sex ratio skew in high road density

        • Road mortality of females on nesting migrations

      • Historical male-biased sex ratio?

        • Proportion of males increased linearly

        • Synchronized with increase in paced roads

      • Indiana Road Mortality

        • Surveyed Lindberg Road for 1.5 years

        • Vertebrate road mortality N=8,176

          • Herps represented n=8, 016

        • Miles of paved roads in Indiana ~93,600

  • Harvest

    • Mostly for commercial exploitation

      • Consumption (food and folk medicines)

      • Luxury trade (leathers, jewelry)

      • Pet Trade

    • Focused on a relatively few spp. in any locality (developing countries)

    • Sustainable harvest by small communities can also decimate populations

    • Examples

      • Consumption: larger, long-lived spp. (Chelonians, specifically the Apalone and also Varanus lizards)

        • 1990’s Europe imported 6,000 tons of frog legs/year

        • India and Indonesia exported 50 million frogs/year

          • Banned exports in 1987 and 1992

          • Depleted natural insecticide from paddy fields

      • Luxury Trade: American Caimans → leather

      • Pet Trade: Box turtle declines in 16 states (~30,000 box turtles since 1995)

        • High prices for rare and brightly colored spp.

  • Introduction of exotic spp.

    • Exotic spp.: Introduced/non-native

      • Black and Norway Rats → great impact on islands (lizards, tuataras, tortoises)

      • Domestic cats → widespread damage in suburban and rural areas

      • Herbivores (goats, rabbits) → change vegetation

    • American Bullfrog

      • Game spp. (frog legs)

      • large

      • High mobility

      • Live 7-9 years

      • Huge reproductive potential

      • Generalized feeding habits

        • Snakes, worms, crustaceans, insects--anything that fits in its mouth

      • California: bullfrogs reduced leopard frog survivorship by 33%

      • Arizona: bullfrogs responsible for leopard frog declines (79 out of 80 sites now extirpated; 79 sites completely devoid of leopard frogs)

    • Management Tools

      • Establishment of refuges and corridors

        • Main objective: prevent extinction

        • Key issue: How much area to preserve?

        • Location, size, and shape of refuges and corridors is dependent on:

          • Whether spp., communities, and/or ecosystems are targeted for conservation

          • Natural history characteristics of the above

        • Minimum Viable Population (MVP)

          • Minimum area required for a population or spp. to survive

          • Studies of terrestrial buffer zones with freshwater turtles

            • Savannah River Ecology Laboratory (SREL)

            • Do protected acreage of wetlands protect areas critical for nesting and hibernating?

              • No, they do not

  • Management of animals in captivity

    • Animals can be managed in captivity for:

      • Short periods (temporary)

        • “Headstart” (from hatchling to 6-12 months)

        • Hatcheries (egg incubation)

      • Long periods

        • Duration of an individual’s life

        • Sometimes several generations

        • Crocodilian farming and ranching

  • Reintroductions of wild spp.

    • Intentional release of individuals to establish or enlarge the population of a target spp.

      • Target spp. usually threatened or endangered

    • Some problems

      • Generally very few of the animals that are re-introduced survive

      • Introduction of diseases into healthy populations

      • Outbreeding depression

  • Pollution

  • Diseases

The Process of Amphibian Conservation: The Eastern Hellbender model

• Phase 1

  • Health & Genetics

    • Sampled 10 states, 70 rivers, and 1200 samples

    • Blood draws for health screens and DNA samples

    • Two large clusters

      • Ohio River Drainage (Indiana, Ohio, West Virginia, Pennsylvania)

      • Tennessee River Drainage (Georgia, Tennessee, North Carolina, Virginia)

      • i.e. Hellbenders in Indiana are genetically similar to those in Ohio

  • Sampling

  • Population Assessment

    • Understand how many Hellbenders you have

      • 88 in Dr. Williams’ case

    • Density

      • 0.06/100m^2

  • Spatial Ecology

    • Health (blood work, sperm, weight class, etc.)

    • Habitat & Home Ranges (radio transmitters and radio telemetry)

    • Hellbenders are very rare; distributed randomly across the landscape with very little interaction between other Hellbenders

  • Survival

    • Annual Hellbender survival if no action is taken: 0.804

• Phase 2

  • Population Manipulation

    • Recovery Strategies

      • Population Viability Analyses

      • Captive rearing and release

      • Translocations

        • Intra-river translocation

          • 10 native adults & 10 translocated adults

        • Captive relreases

          • 10 native adults

          • 10 captive juveniles

        • Spatial Ecology

          • Home range size nearly cut in half (2212 v. 1348 m^2)

          • Extensive HR overlap among individuals

          • Two egg clutches

        • Post-translocation

          • No impact on annual survivorship of adults (80% v. 78%)

          • 50% juvenile survivrship had exceeded 30% threshold to prevent extinction :D

  • Outreach & Education

    • Mail survey

      • 1378 Distributed

      • 281 to Riparian Landowners

      • 541 Completed (41%)

    • In-person survey

      • 242 surveys conducted

      • 6 access sites

    • Focus

      • Awareness, attitudes, behaviour

    • Approach

      • “3D Model” of O & E

        • Develop the portal

        • Design the content

        • Deliver the programs

      • Evaluate impact

      • HelpTheHellbender.org

    • Impact

      • Nationally

        • 25 organizations (6 state/fed agencies, 8 zoos, 11 universities)

        • 63% monthly

        • 82% follow

        • 81% recommend to others

  • Population Modeling

    • 2011-2012, 33 Hellbenders

    • 2018, 5 male Hellbenders

    • Must focus on juveniles

      • Increase juvenile survivorship → expected local extinction in 26 years goes up to 35

        • 30-50% increase → almost completely reverse the probability of Hellbender extinction

      • Problems with heavy predation → low juvenile survivorship

• Phase 3

  • Restoration

    • Captivity can deprive animals of experiences/natural stimuli

      • Predator cues

      • Stochastic events

      • Refuge

      • Live prey

      • Habitat variability

    • Advancing Headstarting

      • Introduce captive, juvenile Hellbenders to natural conditions to better prepare them for the wild

      • Investigate the effects of:

        • Moving water

        • Predator cues

        • Microbiome

      • 90% survivorship in 200 days, then averages around 75%

• Phase 4

  • Providing farmers federal grant money to implement conservation practices in watersheds

The Many Components of Conservation Biology

• Research

• Education/Outreach

• Management

• Captive breeding

• Partnerships

  • A collaboration with many interested bodies

  • Semiannual meetings

  • Action Teams

    • Habitat

    • Outreach & Education

    • Captive Rearing/Breeding

    • Animal Health