Amphibians

Question 1

What does the term “amphibian” mean?

Answer 1

“Amphi” meaning two; and “bios” meaning “life”; so the term Amphibians essentially describes the fact that members of this Class basically have “two lives”.

Question 2

How many species of amphibian in the KNP?

Answer 2

35

Question 3

Do we get newts in RSA?

Answer 3

No

Question 4

What are frog larvae known as?

Answer 4

Tadpoles

Question 5

What do frog larvae feed on?

Answer 5

Primarily algae but small insects and larvae too.

Question 6

What do frogs and toads eat?

Answer 6

Insects primarily but larger species may consume rodents and small birds opportunistically.

Question 7

What is the term given to the transformation of the larval stage to the adult stage in frogs and toads?

Answer 7

Metamorphosis

Question 8

How can frogs stay under water for so long without surfacing for breath?

Answer 8

Frogs have breathable skin and are able to absorb O² from the water around them. This is known as cutaneous respiration.

Question 9

Why do frogs need to keep their skin moist

Answer 9

The moisture on the skin facilitates the transfer of O2 from the air into the animal

Question 10

Name two ways in which frogs have overcome water dependancy? Give an example for each.

Answer 10

• Certain frogs have evolved to live in tree canopies e.g. African Painted Frogs that specialize in living in Bamboo Forests. They have elongated digits for grasping and obtain necessary moisture from that captured in the tree canopy.
• Other frogs have evolved to be more terrestrial e.g the Desert Rain Frog that hatches directly into a fully formed frog rather than metamorphosing. These frogs also aestivate until rain falls.
• The Foam-nest frog (Chiromantis xerampelina) not only employs thermoregulatory colouration and posture; but it also excretes uric acid (as opposed to urine); thus reducing water loss. The giant bullfrog (Pyxicephalus adspersus) buries itself and retains a cocoon of the cornified epidermal layers of moulted skin to prevent water loss.
• The rain frogs (Breviceps spp.) may remain buried for months; emerging only during rainy periods. Some species; like the brown-backed tree frog (Leptopelis mossambicus) may burrow or climb trees to avoid heat uptake and subsequent water loss.

Question 11

Describe two differences between frogs and toads.

Answer 11

1. Toads do not have teeth where frogs do.
2. Toads are normally squatter where frogs are more slender.
3. Toads have dry warty skin where frogs have smooth moist skin.
4. Frogs have fully webbed feet while toads only have partially webbed feet.
5. Toads have parotid glands behind eyes (that secrete bufotoxins) while frogs do not.

Question 12

What is the milky substance secreted from the ridges behind the eyes of a toad when handled? What function does it serve?

Answer 12

This substance is known as Bufotoxin and is a poisonous secretion used as a defence mechanism, it serves to deter predators with either a foul taste or debilitating effect.

Question 13

What frog skips the larval stage? I.e. hatches directly.

Answer 13

The Desert Rain Frog

Question 14

How do frogs’ and toads’ eggs differ?

Answer 14

Toads eggs are in strings while frogs’ eggs are in clumps

Question 15

How do you differentiate sex in frogs from a call?

Answer 15

Only males call.

Question 16

The diagnostically identifiable call in each frog species is for what 3 purposes?

Answer 16

Attracting mates; establishing territories and is a mechanism for spacing males so that each individual is identifiable.

Question 17

In a mating embrace; which sex is on top?

Answer 17

In a mating embrace; the male is on top

Question 18

Which sex is usually larger in adult frogs?

Answer 18

Females are usually larger in adult frogs

Question 19

How do short-limbed rainfrogs; unable to clasp; mate?

Answer 19

They exude an adhesive substance that allows them to stick together while mating

Question 20

What is the easiest way to ID a frog in the wild?

Answer 20

By call.

Question 21

Describe how a foam-nest frog nest is formed?

Answer 21

The male and female; while mating; use their legs to churn the protective jelly that covers the eggs into a foam that will later harden and protect the eggs while they develop

Question 22

What is the function of a foam nest?

Answer 22

Protection of the eggs from predators until they are hatched

Question 23

How long until the eggs hatch in a foam nest?

Answer 23

4 - 5 days

Question 24

Name 2 frog species that don’t lay eggs in water.

Answer 24

• The tadpoles of the Mottled shovel-nosed frog (Hemisus marmoratus) develop on the back of the female frog; underground; and are transported to water at a later stage in their development.
• Many Rain frogs (Breviceps spp.)e.g. The Desert Rain Frog live in very dry conditions in which the chance of surface water for an aquatic larval stage is slight. Large eggs with thick and viscous jelly capsules are laid in underground nests. The aquatic larval tadpole stage is skipped and fully formed froglets hatch from these eggs.

Question 25

What is the term given to the projection of a frogs call which makes them difficult to locate precisely?

Answer 25

Ventriloquism (?)

Question 26

Name two toxic frogs in your area of operation.

Answer 26

The Banded Rubber frog & the Bushveld Rain frog

Question 27

Describe the colouration of the banded rubber frog and why it displays these colours.

Answer 27

The banded rubber frog produces a poison that will agitate the skin and mucous membranes of a predator. It signals this danger through the aposematioc colouration of its skin; the prominent contrasting orange and black colouration signal danger to any would-be predator.

Question 28

Name a species of frog that practices thermoregulation

Answer 28

Foam-nest frog

Question 29

Which frog was used in pregnancy tests?

Answer 29

Platanna

Question 30

Describe the method of testing pregnancy using a frog. What frog species was traditionally used.

Answer 30

The urine of the woman in question would be injected into the frog. The hormones present due to pregnancy would cause the frog to produce eggs within 12 hours of testing. This is due to the presence of the hormone called human chorionic gonadotropoin (hCG). The frog traditionally used was the Common Plattana, Xenopus laevis​.

Question 31

What is the largest species of frog in Southern Africa? How big can it get?

Answer 31

The African bullfrog can grow to 25cm in length

Question 32

What species of of frog do hunters use to poison arrow tips? How do they extract the poison? Where do these frogs occur?

Answer 32

The Poison Dart frog of Columbia is pierced with the arrow and held over a flame or agitated; causing it to release more of the powerful Bufotoxin that it uses for defence

Question 33

What is the largest species of frog in the world? How big does it get?

Answer 33

The Goliath Frog grows to 33cm and appears in Cameroon and equatorial Guinea

Question 34

How far can a grass frog jump? And which species holds the record?

Answer 34

The longest jump by a frog is held by a Sharp-nosed Grass Frog (or “Rocket Frog”) – “Saintjie” jumped over 10 metres in 3 consecutive leaps!

Question 35

Which frogs are unable to jump but walk instead?

Answer 35

The African Bullfrog. The Banded Rubber frog. The Bushveld Rain Frog.

Question 36

Name another type of amphibian besides frogs. Where are they found?

Answer 36

Newts. In South America. (?)

Question 37

Name 6 predators of frogs.

Answer 37

Catfish; herons; storks; kingfishers; certain snakes; rats; lizards; bats;

Question 38

Where are Australia’s problematic cane toads originally from? Why were they introduced?

Answer 38

South & Central America. Introduced in order to control cane beetles.

Question 39

Describe how frogs and toads are indicators of ecological health.

Answer 39

Frogs and toads have breathable skin that is highly sensitive to imbalances in the water they live in. Healthy water systems will usually have a wide variety of healthy populations of various species of frogs

Question 40

What is amplexus and name and describe the three different types.

Answer 40

Amplexus is the mating clasp in frogs. Axillary amplexus is when the male clasps the female behind the front legs (most common). Inguinal amplexus is when the male clasps the female in front of her back legs. Adhesion amplexus is when the female exudes a glue that binds the male to her.

Question 41

What is satelite behaviour?

Answer 41

Satellite behaviour: Silent male frogs in close proximity to actively calling male are tolerated due to their silence. The intentions of this silent “Satellite Male” are to intercept females responding to the calling males.

Question 42

What is time-share calling?

Answer 42

Time-share calling: During a dense breeding chorus; males call alternately to avoid overlap – this assists males to maintain spacing; and allows responding females to be able to pinpoint exact location of calling males

Question 43

Name the 3 main types of vocal sacks in frogs?

Answer 43

1) The median sub-gular sac which has a single lobe beneath the throat - commonly found in South African frogs.
2) The paired sub-gular sac which has 2 lobes which are connected
3) The paired lateral sac which has 2 totally separate lobes.

Question 44

Describe counter-shading in eggs as a defense mechanism.

Answer 44

Top half of egg is a darker shade; helping it to blend into the darker colouration of the bottom of the pool (for predation from above) while the underside of the egg is a lighter shade so that from beneath it blends in better with the lighter sky (for predation from beneath)

Question 45

Frogs and toads may lose up to 40% of their body mass when “aestivating” (inactivity due to dry or hot conditions) without any ill-effects; which they then regenerate by re-hydrating in water. True or false?

Answer 45

True.