Week 7 Sarcopterygians and the origin of tetrapods Flashcards
Describe the characteristics of important extinct species of tetra-pods and how these characteristics allowed colonization of terrestrial environments
limbs and digits
- body support and locomotion
Describe the defense mechanisms of amphibians
-Toxic
-Aposematic
-(some salamanders) have regenerative abilities
- burrowing
Identify and describe the similarities between the 3 orders of amphibian
Similiarties between the 3 orders: Moist permeable skin and undergo metamorphosis
Anura differences from other amphibians
Anura: (1) lack tail (2) compact body, specialized hind limbs for jumping
Caudata difference from other amphibians
Caudata: (1) some can regenerate lost body parts
(2) some stay in their juvenile stage
Gymnophiona differences from other amphibians
Gymnophiona: (1)limbless (2) sensory tentacles used for chemoreception
Sarcopterygian synapomorphies
scales made of cosmine
monobasic paired fin
intracranial joint
What’s special about Tiktalik
It has many terrestrial and aquatic features/shares them. For example, it has a long trunk (fish-like) and it also has the ability to flex elbows (tetra-like)
Important Stem tetrapods
acanthostega
ichthyostega
How do basal tetrapodomorphs and tetrapods compare
-Tetrapodomorph fish- pectoral girdle is attached to the cranial skeleton (no motion in neck area)
-Fin to forelimb
-pelvic girdle, attached to vertebral column in tetrapod
Tetrapod synapomorphies
-hands and feet w/ digits
-loss of fin rays
-oleacranon process on ulna
-zygopophyseal articulations between vertebrae
- modified pectoral/ pelvic girdle—> enlarged to allow weight to be transferred to the limbs
Synap of extant tetrapods
-3 skeletal modifications (allow for greater mobility of the skull)
-Rib modifications that allow for more mobility in central part of the body
-dermal body armor is greatly reduced or absent
-muscular tongue
-eyelids
-middle ear components
Tetrapod is what
a four-footed animal, especially a member of a group which includes all vertebrates higher than fishes
Sarcopterygians are what
(lobbed fin fish) coelacanths and lung fish
What is a Lissamphibian?
-non-amniote tetrapod
-moist, scaleless skin
contains Gymnophiona (caecilians) caudata (salamanders) ans Anura (frogs)
Lissamphibian synap?
you aint gone remember these
(1) Cutaneous gas exchange
(2) skin glands- mucus and poison glands
(3) Bicuspid pedicellate teeth- teeth in which the crown and base (pedicel) are composed of dentine
(lost in many frog species)
(4) Carnivory
(5) Columella operculum complex- transmits high-low freq sound to inner ear
(6) papilla amphibiorum- more hearing
(7) levator bulbi muscle structure- This muscle, present in salamanders and frogs and in modified form in caecilians, is a thin sheet in the floor of the eye socket that is innervated by the fifth cranial nerve. It causes the eyes to bulge outward, thereby enlarging the buccal cavity.
(8)Green rods- In addition to the “red rods” that are found in all vertebrates and are sensitive to green light, salamanders and frogs have green rods, a type of retinal cell that has maximum sensitivity to violet and blue light and is unique to lissamphibians. Caecilians apparently lack green rods; however, the eyes of caecilians are extremely reduced, and the green rods may have been lost.
How do amphibians keep moist?
(1) mucus glands
(2) balance osmotic influx of water by producing dilute urine
(3) Rehydration from limited water sources- pelivc patch
(4) behavioral responses
how does poison differ in lissamphibia?
-toxicity ranged from unpleasant to death
- trophic eggs (tad poles eat mothers eggs to get some toxic defense from alkaloids)
-Aposematic coloration
- poison dart frogs get their lethal compounds from their diet of eating beetles and ants
characters of gymnophiona
(1) dont have girdles/legs
(2) burrowing or aquatic
(3) eyes are greatly reduced and sometimes covered by skin or bone
(4) Annuli- grooves in skin overlying vertebrae
(5) pair of protrusible tentacles on each side of the snout
(6) protrusible copulatory organ in males (phallodeum)
What is gymnophiona
Caecillians
How does gymnophiona reproduce
(1) internal fert
(2) 25% are oviparous and 75% are matrotrophic/vivaparous
Characters of caudata
(1) elongate with 4 function limbs (most)
(2)walking- trot gait combines lateral bending of the body with leg movements
(3) modifications and adaptations
-> paedomorphosis- retention of larval or juvenile characteristics into adult life.
-> stout legs
-> tiny legs
-> loss of sight
-> tongue projections (spring powered)
What is Caudata?
Salamanders
Anuran characters
(1) Specializations for jumping:
->Urostyle
-> 5-9 presacral vertebrae
-> elongated ilium
->hindlimbs longer than forelimbs
-> fusion of tibia and fibula
-> elongate ankle bone
(2)larval stage that undergoes metamorphosis
(3)tail loss in adults
(4)eyes large, placed well forward on head
(5)variation of body forms, locomotion/habitat
(6)sticky tongues (most) and toothless lower jaw
(7) keratinous beaks and denticles on larval mouthparts
Anura reproduction?
2 types
(1) Explosive breeding
(2) prolonged breeding
Explosive breeding
(1:1) sex ratio
usually aquatic breeders in periodic puddles or ponds
prolonged breeding
sex ratio is skewed to have higher males than females at breeding sites
How do anurans attract mates
(1)advertisement calls
(2) in most anurans fert. is external
(3) few species are vivaparous and thus have internal fert.
-> Amplexus, male uses his legs to grasp female
Anuran parental care?
parental care is dependent on clutch size and how the eggs are laid
anuran metamorphosis stages?
(1)premetamorphosis
(2)protometamorphosis
(3)metamorphic climax
premetamorphosis
increase in size of tad-pole
protometamorphosis
hind legs appear, body slowly grows
metamorphic climax
forelegs come out and tail reabsorbs
Why are Lissamphibians vanishing?
Disease
->ranaviruses, carried over from europe to the americas (affects both fish and amphibians)
->Chytrid fungus (stops breathing)
(1) frogs, (Bd) leads to chytridomycosis discovered in late 1980s
(2) salamanders, (Bsal) spreads more rapidly and has a higher mobility rate than Bd
what is Anura
frogs
