Amphibians Flashcards
There is debate on which group gave rise to the amphibians. What is the strongest suggestions ?
That Temnospondyls gave rise to Amphibians and Reptilomorphs gave rise to amniotes.
What are the three groups of amphibians?
- Urodeles: newts and salamanders
- Anurans: frogs and toads
- Caecilians
What are the main Urodeles characteristics?
- Most generalised
- Usually have 4 limbs
- Some have gills as adults
- Most have internal fertilisation
- Same movement seen in the sarcopterygian fish
What are the main characteristics of the Anurans?
- Large and diverse group.
- jumping / swimming.
- Fertilisation usually external.
- Body has shortened - advantage for swimming/ jumping.
- Urostyle - fused vertebrates - makes more robust.
- Long hind limbs (swimming or jumping).
- 4 digits
- Tibia & fibula combined shock absorption.
- Large orbits - well developed eyes - binocular vision.
- Movement and limb length can vary - fore and hindlimbs length can vary
What are the main characteristics of the Caecillians?
- Most specialised
- No appendages
- Legless
- burrowing / aquatic - living in lots of vegetation
- Eyes covered by skin
- Some have dermal scales (not seen in any other amphibian)
- Sensory tentacles
- Internal fertilisation
- Some lay eggs and brood young
- Some birth live young - viviparity
- Some can feed young - vaparine milk
- Annulu folds in skin
What is a toads form of defence?
Poison glands in skin to deter predation
How do frogs hunt?
Jump / ambush / more cryptic - sit and wait (only move when they need to).
What are the conservation issues for amphibians?
- Most threatened taxa (41% threatened with extintion).
- Declining more rapidly than birds and mammals.
- Conservation status underestimated.
- Only 16% of species known.
- Chytridiomycosis - fungus spreading and killing off frogs.
What is unusal about ‘darwins frog’?
- Male raises tadpoles in vocal sac
- Female lays few large eggs
- Male stays with clutch
- Larvae start to produce muscle contractions that stimulate the male to swallow them
- They develop inside the dads vocal sac and come out of the mouth when developed.
Skin
Shared Derived features of Amphibians
- Breath through their skin
- Thin epidermis
- Smooth, moist, permeable (O2 & H20)
What are the issues with having a thin epidermis and breathing through skin?
- Suffer from high rates of water loss
- Need to stay in/near water
Ear
Shared derived features of amphibians
- Use separate regions on the inner ear to detect higher and lower frequencies
- Good hearing in water and air.
- Have an extra bone in the ear compared to any other vert: Operculum columella (function still not fully known).
What region of amphibian ear detects high frequencies and what is it used for?
- Papilla basilaris
- Used to detect mate calls
What region of amphibian ear detects low frequencies?
Papilla amphibiorum
Vision
Shared derived features of amphibians
- Green and red photoreceptors (only red rods in most verts)
- Most amphibians - 4 types of photoreceptors (one more than other verts).
- Can possibly see colours at different light intensities
Pedicellate teeth
Shared derived features of amphibians
- Complex teeth
- Pedicel composed of dentine and separated by connective tissue (the diving zone)
- Connective tissue not calcified
What is the Levator bulbi muscle?
Shared derived features of amphibians
- Muscle that moves the eye only
- Can contract and bulge eyes
- Allows them to enlarge buccal cavity
What are the main shared derived features of amphibians?
- Skin
- Ear (Operculum columella)
- Vision
- Pedicellate teeth
- Levator bulbi muscle
What is unusual about Ceacilian reproduction and parental care?
- Birth live offspring (size = 60% of adults)
- Thought to have internal fertilisation
- Young have specialised feeding teeth
- Mother sheds and regrows skin - providing offspring with food (skin full of fat)
What are the two forms of maternal nutrition in Caecilians?
- Viviparous: Oviductal scraping of uterine milk
- Oviparous: Skin Feeding (skin contains more fat during this stage to become more nutricious to young).
what are the 3 reproductive modes of caecilians?
Oviparous: Aquatic larvae
Oviparous: Direct development
Viviparous: Terrestrial and aquatic
What is the name of the extra bone amphibians have in their ear?
Operculum columella
Other name for caecilians?
Gymnophonia (Apoda)
What has foetal dentition in viviparous Caecilians most likely evolved from?
- Evolved from an oviparous reproduction mode that skin fed.
- Skin feeding is the ancient form and viviparity has most likely evolved from that.
Urodeles reproduction
- Mostly internal fertilisation
- Males deposits spermatophore
- Males have developed complex courting behaviours to get the female to take up their spermatophore.
- Most species lay eggs underwater
- Terrestrial species: (ovo)viviparity - female maintains developing eggs/embryos until the end of gestation
Urodeles courtship behaviours
- Large variety of courtship display
- Pheromone transfer: Tail fanning, Skin slapping, Biting, Rubbing
- Most species lay eggs underwater
What is Paedomorphis?
- When some larval traits are retained into the adult stage.
- Paedomorphosis can be facultative depending on environmental conditions.
Anurans characteristics
- All carnivores
- Can have reduced skeleton
- Skeleton highly specialised for jumping
- Elongated limbs
- Urostyle - shock absorption pelvis
- Short or no ribs
- Tibia and fibula fused to form tibio-fibula
New species of Anurans are constantly being found
- Tolkien frog discovered in 2023 (only one seen).
- Nasikabatrachidae - new family discovered (2003) - first new family described since 1926) - specialised for burrowing.
What is the ancestral larval mode of amphibians?
Thought to be aquatic larvae
Caecilians can no longer reproduce with aquatic larvae
Where are terrestrial reproduction modes most common in amphibians?
Warmer / wetter environments like the Tropics
Why do amphibians lay eggs on terrestrial environments ?
- Predation in aquatic areas in higher
- Species laying eggs on land have increased survival rates
- Risk of predation is lowered but not lost.
What are some amphibian adaptations to overcome difficulties of laying eggs in terrestrial habitats?
- Foam nests - evolved convergently - tropics
- Eggs laid on leaves that overhang water - evolved convergently in 3 groups - tadpoles fall into water - sometimes males protects clutch.
- Viviparity / ovoviviparity - some species show viviparity
1.
When laying eggs on land they have reduced predation but must be protected about desication. What are the trade-offs?
- Bigger eggs - bigger larvae - more chance of survival
- Less eggs
- More costly
- Longer development
- Parental care
- Quality vs quantity
