Amphibians Flashcards
When did amphibians emerge?
Devonian.
What are the three main lineages of amphibia?
- Anura (frogs and toads).
- Urodeles (salamanders).
- Gymnophionans (caecilians).
What happens during frog metamorphosis?
- Small mouth for algal feeding replaced with large mouth for catching prey.
- Herbivorous gut replaced with short gut for carnivorous feeding.
- Legs developed.
- Lungs developed.
- Gills degenerated.
- Tail degenerated.
What are the three periods of metamorphosis?
- Pre-metamorphosis: tadpole gets larger and changes shape a little bit.
- Pro-metamorphosis: hind legs appear and growth slows.
- Climax - forelegs emerge and tail degenerates, very quick process. Vulnerable at this stage as not adapted to aquatic or terrestrial life fully.
What gland is important for metamorphosis?
The thyroid.
What are shared amphibian characteristics?
- Smooth, moist skin.
- Multiple methods of respiration.
- Pedicellate teeth.
- Green vision rods.
- Operculum - columella for hearing.
- Levator bulbi muscle.
How do amphibians prevent desiccation?
- Mucus glands on skin.
- Modifying behaviour.
- Highly vascularised ventral skin absorbs water (pelvic patch).
- Permeable bladder to store dilute urine.
What are the poison glands of some amphibians called?
Parotid gland.
What is cutaneous respiration?
Gas exchange across skin.
What is buccopharyngeal respiration?
Gas exchange in buccal cavity and pharynx.
Explain pulmonary respiration in amphibians.
Amphibian lungs too small for all gas exchange.
- Lack intercostal muscles so cannot expand ribcage.
- Lack diaphragm.
- Use buccal pump which forces air into lungs.
- Air drawn into cavity with glottis closed, nares close and glottis opens, floor of mouth is raised and air is forced into lungs.
What amphibians retain gills?
- Neonetics such as axolotl.
What are advantages of pedicellate teeth?
Flexible to handle prey.
What are green rods?
A photoreceptor unique to amphibians. Not in caecilians as they’re blind.
What is the columella complex?
- Two bones in middle ear which transmit sound to inner ear.
- Dual frequency system: high frequency sounds vibrate columella alone. Low = vibration of operculum-columella unit.
- Used in predator and prey detection.
What is the levator bulbi muscle?
Muscle beneath eye, bulges eye to increase buccal cavity volume. Used in breathing and swallowing.
What is amphibian circulation like?
- Heart has 3 chambers.
- 2 atria and 1 ventricle.
- Right atrium has deoxygenated and left has oxygenated.
- Ventricle divided into two narrow chambers to prevent too much mixing.
What is the amphibian nervous system like?
- 3 brain sections: fore, mid and hindbrain.
- Sensory receptors on skin.
Give characteristics of the Gymnophionans.
- Caecilians - caecilidae largest family.
- Legless.
- Annulated body.
- Very short or no tail.
- Regressed eyes.
- Very solid skull.
- Dermal scales.
- No operculum.
- Curved, relatively long teeth.
- Offspring may be oviparous or viviparous.
- 25% oviparous, 75% vivi.
- Live young are matrotrophic, getting their nutrition from vitellus, then uterine milk.
- Breathe via fetal gills.
Give characteristics of the Urodeles.
- Salamanders and newts.
- Plethodontidae largest family.
- Superficial segmentation.
- 4 equal limbs.
- Male spermatophore = gelatinous base that tapers towards top and support apical sperm mass.
- Male deposits sperm in front of female and female aligns her vent above it and removes the apical mass.
- Some undergo neoteny (larvae become sexually mature before metamorphosis).
- Axolotl is an obligate neonate.
Give characteristics of the Anura.
- Frogs and toads.
- Hind limbs and muscle form lever system, catapulting them forward, fused fibia and tibia.
- Posterior vertebrae becomes urostyle.
- Vocalisation to attract female, fright calls before jumping in water or distress calls if grabbed by wrong sex.
- Amplexus- copulatory embrace where male fertilises eggs that are released by female - external fertilisation.
- Eggs can be developed in or over water, or in a foam or bromeliad nest.
- Parents either carry their eggs, brood them in their mouth or viviparously.
- Suriname toads keep their eggs under their back skin before they erupt through it when ready.
What are threats to amphibia worldwide?
- Habitat loss.
- Climate change.
- Environmental pollution.
- Pathogens and disease. - e.g. chytridiomysis (suffocating fungus)
- Commercial harvest. - mountain chicken.
- Ecological indicators due to their sensitivity to environmental changes.
Give some examples of amphibian families.
- Ranidae - true frogs.
- Bufonidae - true toads (have Bidder’s organ in males).
- Alytidae - midwife toads. (male parental care).
