Lab IV: Biology and Adaptations of Amphibians and Reptiles

Question 1

Feeding Adaptations in Amphibians

Specialization of oral region

Answer 1

• Tongue - highly developed in terrestrial forms (e.g., ranids)
  
  • Tongue attached to anterior of mouth and points backwards at rest
  • Catch living prey that adhere to sticky tip
• Teeth - small and degenerate; do not chew their food
• Oral glands important in terrestrial forms for capturing prey and for swallowing

Question 2

Feeding Adaptations in Amphibians

Swallowing in frogs

Answer 2

• Assisted by tongue and eyeballs
• Jaws close, tongue returns, eyeballs are pulled inward against roof of mouth beneath them
• Eyes press down on tongue, helping to crush food

Question 3

Feeding Adaptations in Amphibians

Feeding

Answer 3

• Amphibians are carnivorous as adults
  
  • Live prey - dependence on sense of vision and tendency to react to moving objects
  • Seek prey, or wait for prey to come to them
• Terrestrial amphibians feed on prey of appropriate size; type of food is variable
• aquatic amphibians feed by snapping motion
  
  • Size is limiting factor
  • Forelimbs create current that brings food closer or to push food into mouth
• Most tadpoles are herbivorous
• Larvae of some species may be cannibalistic

Question 4

Auditory communication

Answer 4

• Organs that create sound by passing streams of air over structures that vibrate
• Air sacs or chambers are used as resonators in some frogs and toads

Question 5

Auditory Communication

Advantages

Answer 5

• Sound passes through vegetation
• Provides greater specificity and complexity than chemical communication
• Precisely timed
• Used at night and in dark environments
• Travels over long distances
• Sound is better than visual signals in getting attention of receiver because sensors do not have to be focused on signaler for message to be received

Question 6

Auditory Communication

Disadvantages

Answer 6

• Cannot convey complex information as rapidly as visual signals
• May alert predators to location of sender
• May be energetically expensive to produce

Question 7

Auditory Communication and Reproduction in Anurans

Answer 7

• Calls convey info regarding species, sex, size, and condition of caller and location of breeding sites
  
  • Calls distinctive to each species, vary in length and pitch
  • Male call is stronger and more distinctive
  • Females have weaker voices
• Males and females have laryngeal apparatus for sound production; males have vocal sac, ventral extension of mouth cavity that acts as resonating chamber
  
  • Produce sound by passing air back and forth over laryngeal apparatus between lungs and vocal sacs at floor of mouth
  • Arrival of “voice” is signal of sexual maturity in anurans

Question 8

Auditory Communication in Other Amphibians (not anurans)

Answer 8

• Caecilians are voiceless
• Salamander lack vocal cords but can emit faint squeaking sound
• Newts possess lunge and larynx and can emit sound
• Frogs and toads have second type of call described as a distress call. Produced with an open mouth and is usually high pitched and loud

Question 9

Locomotion in Amphibians

Salamanders

Answer 9

• Swimming motion of fish
  
  • Uses limbs for paddling and walking, but when frightened, it will tuck them away and swim like a fish (undulations of body)
• Movements of walking salamander are such that vertebral column moves back and forth laterally
  
  • Body is raised up off the ground and propulsion is via a lever action of limbs

Question 10

Locomotion in Amphibians

Saltatory locomotion in frogs

Answer 10

• Adaptations seen in saltators:
  
  • Hindlimbs are greatly lengthened
  • Forelimbs are not long, generally used for grasping or slow locomotion
  • Neck is short and solid, may even have fused vertebrae

Question 11

Locomotion in Snakes

Serpentine or lateral undulation

Answer 11

• Body is thrown into serpentine or S-shaped loops, right and left
• Locates with coils projections, like pebbles and plant stems
• Body presses sideways against objects in direction that is obliquely backward relative to direction snake is to move

Question 12

Locomotion in Snakes

Concertina

Answer 12

• Draws itself into one of more S-shaped coils
• Posterior coils press downward and backward against substrate, relying on friction to prevent slippage
• Thrust is used to advance head and anterior part of body forward

Question 13

Locomotion in Snakes

Sidewinding

Answer 13

• Sidewinding for fast and efficient travel over loose or sandy soil
• Makes series of undulations at about a 60-degree angle with movement in tracks that are more or less in a straight line
• Desert snakes

Question 14

Locomotion in Snakes

Rectilinear

Answer 14

• Enables snake to advance in straight line
• Snake pulls together two sets of scutes and fixes them against ground (creates friction, snake propels itself forward)
• Tenses bands of muscles running from scutes back towards ribs

Question 15

Feeding Adaptations in Reptiles

Oral Cavity

Answer 15

• Well-developed lips, but non-muscular and non-moveable
• Some specialized forms (e.g., turtles beak)
• Tongue - composed of various muscles with skeletal support from first or second visceral arches
  
  • Non-protrusible tongue in turtles
  • Protrusible tongue in everything else
• Teeth
  
  • Lacking in adult turtles and tortoises (found in embryos of soft-shelled turtles)
  • Other reptiles have well developed teeth along margins of upper and lower jaws
  • Snakes have backwardly recurved or slanted uniform, attached to jaw by fibers or roots
  • Three divisions of snake teeth: solid, grooved, and hollow (latter two are for passage of venom into prey)
    *

Question 16

Feeding Adaptations in Reptiles

Cranial Kinesis

Answer 16

• Cranial kinesis = motion of several elements of skull relative to each other. Kinetic skulls are divided into movable units that are linked together and function together to elevate and depress the upper jaw
• Lizards have kinetic skulls with four principal units - allows upper jaw to bite down on food and to manipulate food by moving relative to lower jaw
• Kinetic mechanism of snakes may include many units (eight in boa) that are loosely joined together and independent on two sides of hear. Infinite variety of relative motions is possible

Question 17

Feeding Adaptations in Reptiles

Sensory Mechanisms

Answer 17

• Reptiles use wide variety of senses to detect their food:
  
  • Turtles - keen sense of vision and use this, along with olfaction, in detecting food
  • Lizards primarily use eyesight
  • Snakes use eyes, Jacobson’s organ (accessory olfactory organ) to detect prey
    
    • Some snakes also have heat pits that lead to heat-sensing organs that they use to sense their prey