Amphibians

Question 1

Name the 3 orders of amphibian

Answer 1

Gymnophiona - caecilians 205 spp.
- 3% of amphibian spp.
- subterranean 
Caudata - newts/salamanders 683 spp.
- 9% of amphibian spp.
- aquatic/terrestrial forms
Anura - frogs/toads 6640 spp.
- 88% 
- mostly terrestrial

Question 2

What are the common characteristics of modern amphibians?

Answer 2

Tetrapods (except caecilians)
Ectothermic
Reliant on aquatic environments
Permeable skin: moist and glandular
- glands in skin discharge mucus which keeps the skin moist important in skin respiration and thermoregulation
- also protects against bacterial infections and moulds as well as making it slippy
Most amphibians have aquatic eggs and a larval stage with gills
- cutaneous respiration in adults
Undergo metamorphosis

Question 3

What hormones are responsible for the metamorphosis of anurans? And which amphibians retain a permanently aquatic existence?

Answer 3

Thyroid hormones induce metamorphosis prolactin has an inhibitory effect

Newts

Question 4

Give an example of an amphibian that has adapted to survive in very dry environments

Answer 4

Desert rain frog - Breviceps macrops

Question 5

What defence mechanisms do amphibians utilise?

Answer 5

Aposematic colouration
Poison glands
- granular glands in integument produce poison
- phyllobates, one of the most lethal animal secretions known
Mimicry

Question 6

Describe the order Gymnophiona

Answer 6

10 families - 205 species
Caecilians also called Apoda
Burrowing or aquatic
Habitat - tropical forests
Have many vertebrae
Some lay eggs, others are viviparous 
Modified to live in subterranean worlds, strong skull with pointed snout to push through soil or mud. Adapted muscles for pushing. Small eyes covered by skin for protection. Additional olfactory tentacles
Only order of amphibians to reproduce exclusively by internal fertilisation . 25% oviparous 75% viviparous

Question 7

How many species are in the class amphibia? Give an account of their evolution

Answer 7

7,500 species
First land tetrapods ~370 Mya
Lissamphibia appeared around 300 Mya 
Gave rise to all extant amphibians 
Evolved from terrestrial fish - tiktaalik roseae

Question 8

Give an example of a species in the order Gymnophiona

Answer 8

Boulengerula taitana - feeds young by developing outer layer of skin high in fat and other nutrients which the young peel off with modified teeth

• allows them to grow up to ten times their own weight in a week
• skin consumed every three days

Question 9

Describe the order Caudata

Answer 9

Newts (aquatic) and salamanders (terrestrial)
Have tails, short legs at the side of their body and use lateral undulations of body to walk or swim
Fertilisation is internal in around 90% of species
Deposition and collection of spermatophore

Question 10

Describe caudate physiology

Answer 10

Costal grooves - keep skin moist by channeling water over body surface
Tail used in courtship and as a storage organ for protein and lipids, also functions as a defence mechanism
Adult salamanders can regenerate limbs
Salamanders also shed and eat their skin
Can produce repellent toxic secretions

Question 11

Give an example of a toxic Caudate

Answer 11

Rough skinned newt (Taricha granulosa) produces the neurotoxin tetrodotoxin, the most toxic non protein substance known

Question 12

Describe the order Anura

Answer 12

Frogs and toads
Specialised pelvis and hind limbs for jumping
Many have dramatic metamorphosis from larvae to adults
External fertilisation
55 families, 6500 spp (most successful amphibian group)
Only 9 trunk vertebrae, rod like urostyle, feet 5 rayed hands 4

Question 13

What are the characteristics of a toad?

Answer 13

Short legs
Stout bodies
Thick skins
Prominent warts
Paratoid glands 
True toads belong to family Bufonidae

Question 14

Give an example of parental care in Anura

Answer 14

Surinam toad (Pipa pipa) - allows offspring to grow on her back beneath skin until they are ready to leave