The Amphibians

Question 1

Facts about the amphibians

Answer 1

• over 7000 species - largest Anura

* oldest fossil to fate from ~290mya in Permian which shows both urodele and anuran

Question 2

3 groups…

Answer 2

1. Urodeles - salamanders and newts
2. Anuran - frogs and toads
3. Gymnophiona - caecilians

Question 3

Shared characteristics of amphibians

Answer 3

• Smooth, moist permeable skin - water and O2 can pass
• Papilla amphibiorum - auditory mechanistic in inner ear, important for communication
• Operculum-collumella complex in the ear, important for hearing and communication
• Green rods- assists with night vision (not in caecilians)
• Pedicellate teeth - pedical composed of dentine and separated by connective tissue
• Neurones have levator bulbi muscle - allows enlarged buccal cavity - pushes eyes forward

Question 4

Urodele features

Answer 4

500 species worldwide
•most basic body structure - fish with legs
•4 limbs, but some very aquatic forms have lost or reduced limbs
•locomotion is movement in a very undulatory way (like lungfish)

Question 5

Urodele reproduction and development

Answer 5

•large variation in courtship display - can be very complex with elaborate secondary sexual characters
-visual and pheromonal cues for mate attraction
•pheromone transfer by tail fanning (aquatic) or skin slapping, biting or rubbing
•aquatic eggs and larvae - viviparity in purely terrestrial spp
•some show paedomorphosis/neotony - reproduction during the larval stage (cave-dwelling - axolotl)
-some show facultative paedomorphosis depends on ecological conditions

Question 6

Gymnophiona morphology

Answer 6

180 species - blind
•folds of skin look like segments 
•eyes can be covered in skin or bone
•can have dermal bone in skin
•lost legs for burrowing or living in aquatic-vegetation filled environments
•worm-like

Question 7

Gymnophiona reproduction and development

Answer 7

•internal fertilisation sperm transferred by adapted cloaca
•egg-laying or viviparous - can have up to 9 offspring, birth already 60% body length
-small number, high investment
•energy for growth from yolk
-mother produces uterine milk
-young eat mothers skin - regrown every 3 days as supports rapid growth
-specialised foetal dentitions for scraping oviduct wall
•foetal fill for gas exchange across oviduct walls - potentially exchange of metabolic waste

Question 8

Risk to amphibians

Answer 8

•most endangered of all groups
•habitat specialists - more vulnerable to habitat change, climate etc.
•chitard fungus had les to populations being wiped out
-fungus has been spread by humans