ZOOL 406 - Amphibian Lab Material

content from Dr. Alison Murray and TA Declan Rourke

What are the three extant amphibian groups?

• Caudata (salamanders)

• Anura (frogs and toads)

• Gymnophiona (caecilians)

  • All orders

What is metamorphosis?

Reorganization of the body to change from generally aquatic larval form to (generally) terrestrial adult form

What does the beginning of most amphibian life look like?

Eggs are deposited in water and hatch into larvae (bill-bearing larval salamanders or tadpoles)

• Larval stage length varies (7 days - 3 years)

What are some exceptions to an aquatic larval stage?

In some terrestrial habitats, the eggs undergo direct development and hatch into miniature adults

What are some changes seen in metamorphosis?

• Regression of gills, formation of lungs

• Degeneration of tail and tail muscles (anurans)

• Development of limbs

• Formation of dermal glands

• Reorganization of the intestinal tract including switch from herbivorous to carnivorous diet

• Modifications of excretory system with switch from ammonia waste to urea in some forms

• Loss of tail “fins” in some salamanders

Do all amphibians undergo complete metamorphosis?

No.

What are some shared traits of all amphibians?

1. Mouth usually large; small pedicellate teeth in upper or both jaws; two internal nares open into anterior part of mouth cavity.

2. Forelimbs of some much smaller than hind limbs, in others all limbs small; webbed feet often present; no true nails or claws; forelimbs usually with 4 digits but some have 5 and sometimes fewer; some are legless

3. Moist, permeable skin – it is a major respiratory surface, and one that limits the habitats available to these animals

4. Skin glands – the integument is also important in terms of the glands that are present, and pigments that are part of courtship behaviors and defensive mechanisms

What does jaw articulation look like in amphibians?

Jaw articulation is between the articular (lower jaw) and quadrate bones (upper)

What does an amphibian spinal cord look like?

Mostly bony with varying number of vertebrae with zygapophyses (extensions which join one vertebra to the next); notochord does not persist in living forms, unlike early fossil tetrapods

What do amphibian body forms look like?

Body forms vary greatly from elongated trunk with distinct head, neck and tail to a compact, depressed body with fused head and trunk and no intervening neck

What are some skin characteristics you’ll find in most all amphibians?

Skin smooth and moist with many glands (mostly mucus), some of which may be poison glands; pigment cells (chromatophores) common and of considerable variety

What are chromatophores?

Pigment cells in skin

What are the three types of colouring seen in amphibians?

1. Cryptic

2. Aposematic

3. Mimicry

What is cryptic colouring?

Skin resembles background

• Protection from predators

What is aposematic colouring?

Amphibian is brightly or conspicuously colored but noxious

• Warns away smart predators that remember a past unpleasant experience with a brightly colored prey and avoid it the next time

What is mimicry?

Amphibian resembles a poisonous or aposematic species but is not actually poisonous itself

Is amphibian skin always smooth?

No, sometimes it contains keratinized structures

• Eg. spadefoot toad

What adaptations are found in amphibian skin that help with cutaneous respiration?

• Highly vascularized

• Brumation (like hibernation) occurs in some species whereby successive molts are retained to prevent desiccation (water loss)

• Frogs uptake water through pelvic patches

• Hellbenders (cryptobranchidae) have highly vascularized skin folds

• Warts may be found on the skin of most anurans

• Specialized mucous and poisons glands are found in some species

  • Poison glands are concentrated in strategic areas

    • Eg. parotid glands

What does the circulatory system look like in amphibians?

Three-chambered heart, two atria and one ventricle; adults with double circulation (i.e., pulmonary circuit)

• Skin abundantly supplied with blood vessels (cutaneous respiration)

What does the respiratory system look like in amphibians?

Respiratory organs include lungs (absent in plethodontid salamanders), skin, and gills

• External gills in the larval form and may persist throughout life in neotenic forms

What does reproduction look like in amphibians?

Sexes separate

• Mostly internal fertilization in salamanders and caecilians

• Mostly external in frogs and toads

What are the three main styles of reproduction/birth seen in amphibians?

• Predominantly oviparous (egg-laying)

• Some ovoviviparous (eggs develop without maternal nourishment and hatch internally)

• Viviparous (bear live young)

What are the two main measurements taken of amphibians?

• Snout-vent length (SVL)

• Tail length

What is SVL?

Snout-vent length - measured from the tip of the snout to the caudal end of the cloacal aperture

• Anurans normally measured from tip snout to caudal end of urostylar projection (vent is often difficult to find)

What is tail length?

Measurement taken from the caudal end of the cloacal aperture to the tip of the tail

• Note and measure separately any part of the tail that has been regenerated

What are some methods for marking amphibians?

• Toe clipping

• Pattern mapping

• Passive integrated transponder (PIT) tags

• VIE tags

  • No need for specifics, just know these methods exist

What is Lissamphibia?

Group that encompasses the three major living groups of amphibians (anurans, caudata, gymnophions)

• NOT monophyletic → doesn’t include any fossils/ancestors

What is order Anura?

“Tail-less” frogs and toads

How does a frog’s body proportions reflect its saltatory locomotion?

• Lengthened hind limbs, shortened forelimbs (for grasping)

• Short, solid neck

• Fused vertebrae

  • Posterior vertebrae fused into a single strong element

What are some features found in frogs?

• Dorsolateral ridges

• Parotid glands

• Nuptial pads

• Expanded finger tips

What are dorsolateral ridges?

Found in ranid frogs → contain concentrations of poison glands

What are parotid glands?

Found in bufonid toads → contain concentrations of poison glands

• Located behind eyes

What are nuptial pads?

Anuran accessory breeding structures on one digit of each forelimb

• Used to help male grip female in amplexus

What are expanded finger tips?

Found in tree frogs → contain glands that produce a sticky secretion that “glues” them to trees, rocks, etc

What characteristics do we look at when identifying anurans?

1. Cranial bones

2. Pectoral girdle

3. Vertebrae

4. Presacral ribs

5. Sacrum-urostyle articulation

6. Shape of terminal phalanges

What are the main cranial bones found in frogs?

• Palatine

• Frontoparietal

What is a palatine?

Cranial bone in frogs that is typically reduced to a thing bridge between the maxilla and vomer in modern anurans, reduced even in fossil forms

What are the primitive and derived conditions of the palatine?

Present - Considered primitive

Absent - Considered derived, fused to the point of absence with either vomer or maxilla

What is the frontoparietal bone?

Cranial bone in frogs → can by fused or paired

• Fossil frogs can display both states or even absence

What are the primitive and derived conditions of the frontoparietal bone?

Paired → Considered the primitive state, but lasts into many modern groups

Fused into a single element → Considered derived, but appears in some fossil lineages

What are the two conditions of the anuran pectoral girdle?

• Arciferal

• Firmisternal

What is the arciferal pectoral girdle?

Condition of the anuran pectoral girdle where epicoracoid cartilages are fused anteriorly, but are separate and overlapping posteriorly

What is the firmisternal pectoral girdle?

Condition of the anuran pectoral girdle where epicoracoid cartilages are fused anteriorly and posteriorly, and usually have an omosternum present

What are the primitive and derived conditions of the anuran pectoral girdle?

Arciferal → considered primitive

Firmisternal → considered derived in some groups

What do vertebrae look like in anurans?

High number than five indicates a more primitive frog/toad

• Advanced = fused = less vertebrae

What are the three conditions of anuran vertebrae?

• Opisthocoelous

• Procoelous

• Amphicoelous

What are opisthocoelous vertebrae?

Anterior surface of centra is convex, posterior surface is concave

What are procoelous vertebrae?

Anterior surface of centra is concave, posterior surface is convex

What are amphicoelous vertebrae?

Both anterior and posterior surface of centra are concave

What do presacral ribs look like in anurans?

Can be present or absent, but most modern anurans display the absent condition

What do present presacral ribs look like in anurans?

Can vary in number, all classify as free ribs (not attached to a sternum)

What do absent presacral ribs look like in anurans?

Transverse processes of the presacral vertebrae lengthen to support the thoracic elements in the place of free ribs

What are the primitive and derived conditions of presacral ribs in anurans?

Present → considered primitive

Absent → considered derived

What is sacrum-urostyle articulation?

An essential joint for the saltatory locomotion primitive to anurans

• Functions by extending and dorsoventrally aligning the urostyle and ilia with the trunk, thereby transferring the energy from a jump to the center of gravity of the frog

What are the four different conditions of sacrum-urostyle articulation?

• Cartilaginous

• Reduced/lost zygapophysial articulations

• Bicondylar

• Fused

What is cartilaginous sacrum-urostyle articulation?

No bony impediment to extension

• Associated with the purely saltatorial motion primitive to all anurans

What is reduced/lost zygapophysial sacrum-urostyle articulation?

Eliminates vertebral constraint on extension

• Also associated with saltatorial locomotion

What is bicondylar sacrum-urostyle articulation?

Reduces joint to purely hinge-like flexion/extension

• The most common condition

• Found in frogs that are capable of saltation, but tend to be terrestrial or arboreal ‘walkers’ and ‘climbers’

What is fused sacrum-urostyle articulation?

Eliminates all movement of the joint

• Associated with the inability to jump

• Found in burrowing walkers and purely aquatic forms

  • Morphology reported for Pelobatidae and Pipidae

What does the shape of terminal phalanges tell us about anurans?

Can be loosely correlated with the presence of claws and/or finger pads

What are the three main shapes of terminal phalanges found in anurans?

• Pointed

• Blunt

• Bifurcated

What do pointed terminal phalanges say about anurans?

Indicating presence of ‘claws’ or hardened finger tips and a burrowing or aquatic habit in which superior grip is needed

• May also have expanded finger pads if intercalary cartilage is also present proximally

• Webs for aquatic, keratinous epidermis for fossorial

What do blunt terminal phalanges say about anurans?

Indicating a broad terrestrial/aquatic habitat

What do bifurcated terminal phalanges say about anurans?

Indicating the presence of broad finger pads and a climbing habit

What are tadpoles usually stored in?

Formaldehyde → they’re too squishy for other alcohols, they will literally disintegrate

Diagram of different tadpole measurements

Diagram of different tadpole mouth features

Photo of tadpole mouth

What are the 10 anuran families found in North America?

1. Ascaphidae/Leiopelmatidae

2. Pelobatidae/Scaphiopodidae

3. Rhinophrynidae

4. Pipidae

5. Leptodactylidae/Eleutherodactylidae

6. Hylidae

7. Dendrobatidae

8. Bufonidae

9. Microhylidae

10. Ranidae

What are the 8 anuran species found in Alberta?

1. Spea bombifrons – Plains Spadefoot Toad

2. Bufo boreas – Western Toad

3. B. cognatus – Great Plains Toad

4. B. hemiophrys – Canadian Toad

5. Pseudacris maculata – Boreal Chorus Frog

6. Rana luteiventris – Columbia Spotted Frog

7. R. pipiens – Northern Leopard Frog

8. R. sylvatica – Wood Frog

What is the common name of family ascaphidae?

Tailed frogs

• May be a subfamily of Leiopelmatidae

What are some characteristics of family Ascaphidae/Leiopelmatidae?

Copulatory/intermittent organ found only in males forms a “tail” – it is in reality formed by the cloaca and associated muscles

• Lack of palatine bone (derived)

• Paired frontoparietal bones (primitive)

• Arciferal pectoral girdle with distinct sternum (primitive)

• 9 amphicoelous presacral vertebrae (primitive)

• Free ribs on vertebrae 2-5 (primitive)

• Cartilaginous sacrum-urostyle connection (saltatorial)

• Blunt to pointed terminal phalanges (aquatic)

What is the biology of family Ascaphidae/Leiopelmatidae?

• Nocturnal

• Clear mountain streams

• Voiceless males

What does reproduction look like in family Ascaphidae?

• Internal underwater fertilization

  • Females store sperm long-term (9 months)

  • Eggs laid in fast moving water with larval stage lasting 2-3 years

    • Non-ascaphid Leiopelmatids do direct development (no larval stage)

What species of Ascaphidae are found close Alberta?

• Ascaphus truei

• Ascaphus montanus

What is common name for family Pelobatidae?

Spadefoot toads

What are some characteristics of family Pelobatidae?

Squat toads with warty but soft skin; Crescent-shaped horny projections on side of hind foot, primarily used for digging

• No palatine bone (derived)

• Paired frontoparietal bones (primitive)

• Arciferal pectoral girdle with distinct sternum (primitive)

• 8 amphicoelous presacral vertebrae (primitive)

• Bicondylar sacrum-urostyle articulation (walker/climber)

• Blunt terminal phalanges (fossorial)

What is the biology of family Pelobatidae?

Fossorial → burrowing backwards and spending the majority of their lives underground

• Depending on environment, has 2–3 month or 1–3 year larval period

  • Large tadpoles if latter period, resulting in largest European tadpole

What does reproduction look like in family Pelobatidae?

Males chorus around temporary ponds in which eggs are soon deposited

• Quick, annual reproduction can be completed in a single period

• Nearctic form known for explosive reproductive habits: after heavy rains

• Larval stage can be as rapid as 6 days, though usually about a month long

What species of Pelobatidae is found in Alberta?

Spea bombifrons - plains spadefoot

• Could be in its own family Scaphiopodidae

What is the common name for family Rhinophrynidae?

Mexican burrowing toad

• Pancake frogs

What are some characteristics of family Rhinoprhynidae?

Tiny, cone shaped head, short, robust limbs and large, fat, pancake body

• Lack palatines (derived)

• Single frontoparietal bone (derived)

• Arciferal pectoral girdle that lacks a sternum (primitive)

• 8 opisthocoelous presacral vertebrae (primitive)

• Bicondylar sacrum-urostyle articulation (walker/climber)

• Blunt terminal phalanges (fossorial)

What is the biology of family Rhinoprhynidae?

• Fossorial devastators of subterranean arthropods

• Equipped with epidermal snout armor, double sealable lips, and a tongue that can project straight out of the mouth

• Also with hind limbs, possessing spades on the inside edge of the hind feet

What does reproduction look like in family Rhinoprhynidae?

• Calling males float in temporary pools

• Females eventually deposit several thousand sinking eggs that hatch into tadpoles that aggregate

• Develop their lower jaws early and can cannibalize each other

What is the common name for family Pipidae?

African clawed frogs and Surinam toads

• Introduced in North America

What are some characteristics of family Pipidae?

Dorsoventrally flattened tongueless adults that still possess a lateral line system, with thick waists, heavy legs and large webbed hind feet

• Lack palatines (derived)

• Single frontoparietal bone (derived)

• Arciferal pectoral girdle with a small sternum (primitive)

• 6-8 opisthocoelous presacral vertebrae (primitive)

• Fused ribs present on the vertebrae 2-4 (primitive)

• Bicondylar-fused sacrumurostyle articulation (walker/climber)

• Pointed terminal phalanges hardened into claw-like structures (fully aquatic)

What is the biology of family Pipidae?

• Most use their forefeet in feeding

• Fully aquatic → found in still or slow moving water among vegetation

What does reproduction look like in family Pipidae?

• Perform elaborate breeding behaviors involving a series of somersaults

• Male to fertilize the eggs and either place them under floating vegetation, in a pocket of skin that forms on the female’s back, or hold them against the female’s back in order for them to fully embed in the dorsal skin

• Can be direct or indirect development.

What is the common name for family Leptodactylidae?

White-lipped frogs and tropical grass frogs

• Free-toed frogs could be their own family Eleutherodactylidae

What are some characteristics of family Leptodactylidae?

Can be very large

• Paired palatine bones (primitive)

• Paired frontoparietal bones (primitive)

• Modified arciferal pectoral girdle with a distinct sternum [pseudofirmisternal → appears to have fused-up] (between primitive and derived)

• 8 procoelous presacral vertebrae (primitive)

• Bicondylar sacrum-urostyle articulation (walker/climber)

• Variable terminal phalanges (terrestrial)

What is the biology of family Leptodactylidae?

• Terrestrial

• Not in Canada, too cold and dry

What does reproduction look like in family Leptodactylidae?

• Eggs deposited in foam nests in a variety of ways:

  • On top of water

  • In shallow depressions or burrows near ponds to be washed into ponds with heavy rain

  • In terrestrial depressions where the female will deposit tropic eggs to feed the tadpoles, or have endotrophic tadpole

What is the common name for family Hylidae?

Amero-Australian tree frogs

What are some characteristics of Hylidae?

Tiny to giant, slender and long legged with blunt head

• Paired palatines (primitive)

• Paired frontoparietal bones (primitive)

• Arciferal pectoral girdle with a distinct sternum (primitive)

• 8 procoelous presacral vertebrae (primitive)

• Bicondylar sacrum-urostyle articulation (walker/climber)

• Pointed terminal phalanges → toes often tipped with expanded discs (generally arboreal)

What is the biology of family Hylidae?

Most are arboreal, though the Albertan species is one of the few terrestrial species

What does reproduction look like in family Hylidae?

• Males call and females deposit eggs in wide ranging aqueous habitats from tree holes and bromeliads to lakes and streams

• Some species have parental care:

  • Male nestmaking and egg-guarding

  • Trophic egg deposition in bromeliads to feed hatched tadpoles

What species of Hylidae is found in Alberta?

Pseudacris maculata - Boreal chorus frog

What is the common name for family Dendrobatidae?

Poison frogs

What are some characteristics of family Dendrobatidae?

Boldly colored (aposematic) skin with numerous poison glands

• Paired palatines (primitive)

• Paired frontoparietal bones (primitive)

• Firmisternal pectoral girdle with a distinct sternum (derived)

• 6-8 procoelous presacral vertebrae (primitive)

• Bicondylar sacrum-urostyle articulation (walker/climber)

• T-shaped (bifurcated) terminal phalanges (arboreal)

  • Possess a small pair of bony plates on ends of digits called supradigital scutes

What is the biology of family Dendrobatidae?

Diurnal frogs found in riparian, terrestrial or semiarboreal microhabitats in tropical rainforests

• Derives some alkaloid toxins from their diet of ants