Lecture 5 Class Amphibia amphi both bios life

Lecture 5: Class Amphibia amphi ‘both’ + bios ‘life’ Part I: Early Tetrapods and Caudates (Salamanders) Ch. 25 pp. 546 -555 The Spotted Salamander

A. Movement onto Land 1. Land is hazardous Life originated in H 2 O Animals are mostly H 2 O Cellular activities occur in H 2 O 2. Accommodations Ability to get O 2 out of air Air is much less dense than H 2 O Temperature fluctuations are much greater Environmental differences Model of Acanthostega, an extinct tetrapod that was among the first vertebrates to have evolved limbs. .

I. Evolution B. Geologic Time: Devonian Period 1. Time ~ 400 mya Bony fishes diversified to include freshwater forms 2. Evolution of Structures Pharynx connected to air filled cavity (swim bladder) Internal nares

I. Evolution 3. Early Evolution Extinct Genus Acanthostega • • • 8 webbed digits on each hand Fish-like shoulder and forelimbs Short lungs, unsupported by chest cavity out of water Internal covered gills Lived in shallow, weedy swamps

I. Evolution C. Adaptive Radiation 1. Pressure to Diversify Caused by environmental changes 2. Unstable Freshwater Environment Frequent drying periods Low oxygen 3. Suitable Land Environment Habitat: Large protective ferns Food: Terrestrial insects 4. New Traits Developed Lungs Limbs

I. Evolution D. Geologic Time: Permian Period 1. Ancestor Class Lissamphibian (all others extinct) Characterized by: • • Four digits on forelimb Large, round head and shortened vertebral column Extinct Genus Gerobatrachus

II. Order Caudata (Salamanders) A. General Characteristics -360 species of tailed amphibians 1. Most are in northern temperate regions 2. Some in tropics of Central & South America B. Body Form -Similar to ancient ancestors 1. 15 cm 1. 5 m long 2. Forelimbs and hindlimbs set at 90°

II. Order Caudata (Salamanders) C. Body System 1. Skeletal/Muscular -Bony skeleton Distinct head, neck, trunk & tail Jointed limbs; some very reduced Long tails; some highly modified for propulsion in water. This is a cleared and stained specimen of the Austin Blind Salamander. The “clearing” process makes proteins transparent while the “staining” stains all cartilage blue and bone red. This is a very useful technique to allow researchers to study the bone structure of an amphibian without destroying the connective tissue.

II. Order Caudata C. Body Systems 2. Respiratory a. Skin/Mouth Breathing Vascular nets underneath the skin • Cutaneous (skin) respiration; most N. American species Supplemented with buccal (mouth) breathing § Vascular membranes in the buccal cavity. b. Other Adaptations Aquatic stages may have external gills or lungs Terrestrial forms with external gills or lungs No gills or lungs at all; entire cutaneous/buccal breathing c. Species with Lungs Present in larvae that are terrestrial as adults; become functional after metamorphosis.

II. Order Caudata C. Body Systems 3. Circulatory System a. Lungless & Lungless/Gillless Salamanders n 2 -chambered hearts like fish n Single loop system b. Lunged Salamanders n 3 -chambered heart n Double loop system 2 -chambered heart 3 -chambered heart One ventricle (pump) Two atria (holding sacs) Atrium fills with blood from body goes to lung to pick up oxygen back to other atrium out ventricle to rest of body

II. Order Caudata C. Body Systems 4. Nervous System Well developed nervous and sensory system a. Eyes move in socket and have a protective structure = nictitating membrane is a transparent membrane that covers the eye when the frog is in the water b. Tympanic membrane = eardrums (also lung can help)
 c. Lateral Line systems = detect water movement (vibrations)

II. Order Caudata C. Body Systems 5. Digestive System a. Feeding Carnivorous as larvae and adults Small arthropods, molluscs, and worms Prey must be moving b. Digestive Tract mouth > esophagus > stomach > small intestines > large intestine (colon) > cloaca c. Metabolism Not much fat or glycogen storage Ectotherms with low metabolism

II. Order Caudata C. Body Systems 6. Reproduction a. Dioecious b. Breeding n n n In water or on land Internal fertilization via spermatophore Mostly oviparous c. Most Undergo Metamorphosis d. Variety of mating habits & development Four-Toed-Salamander Reproduction

II. Order Caudata C. Body Systems 6. Reproduction e. Paedomorphosis Retention of juvenile characteristics as adults Some will undergo metamorphosis if “good” environmental conditions are present Mexican salamander (Ambystoma mexicanum) During courtship, a pair of axolotl will be seen doing a 'waltz' with both animals moving in a circle. This leads to the male shaking his body, resembling a 'hula dance' with the female then mimicking his moves.

II. Order Caudata D. Environmental Issues Biological Indicators of the Environmental Health a. Giant Hellbender -US salamander declining due to unhealthy streams, disease n Hellbender Research at the Smithsonian