Reptiles, Amphibians and Fish

Question 1

What are some common features of reptiles?

Answer 1

• Low metabolic rate (high anaerobic capacity)
• Ectothermic = derive energy from external heat source
• 3 chambered heart (most reptiles)
• No seperate thorax and abdomen = one coelomic cavity
• Scales

Question 2

How does thermoregulation in mammals differ to reptiles?

Answer 2

Mammals are endotherms “warm blooded”
- Under normal conditions can maitain deep body temperature regardless of environmental temperature
- Rely on metabolic heat production
- Costly (need lots of food for energy)

Reptiles = ectotherms
or poikilotherm (temperature the same or similar to the environment)

Question 3

Define Preferred Optimal Temperature Zone (POTZ) ?

Answer 3

Temperature range of natural habitat (may vary seasonally) metabolism is most efficient within this zone.
Importat for giving medicine so it can be metabolised effectively

Question 4

What is the reason some animals are ectotherms vs. endotherms?

Answer 4

Depends on their needs - consider:
1. Activity level
2. Dependence on environment
3. Metabolic rate vs. energetic cost
4. Ambient temperature variation
5. Availability of food/energy
6. Behavioural thermoregulation
7. Insulation

Question 5

Describe the general CVRS of reptiles

Answer 5

3 chambered heart with 2 atria and 1 ventricle in all reptiles except crocodilians
- Ventricle split into three parts (cavum venosum, cavum pulmonale and cavum arteriosum)
- Hepatic and renal systems: Important to maintain circulation to the kidneys at times of water deprivation, blood from caudal 1/3 of reptile pass via liver or kidneys prior to returning to the heart.

Question 6

What are the advantages and disadvantages of the reptile CVRS?

Answer 6

Advantages:
- Can cut the lungs out of the circulation when there is no oxygen available and rely on anaerobic metabolism
Disadvantages:
- Unhelpful for anaesthesia when attempting gaseous induction
- Drugs administered into caudal 1/2 to 1/3 may have varying effects and could cause toxicity

Question 7

Describe the respiratory system of reptiles

Answer 7

• No diaphragm
• Breathing occurs via active movements
• Simple lungs which can be single chambered, have a few chambers or have multiple chambers depending on the species needs
• Low surface are of the lungs for gas exchange

Question 8

What are the advantages and disadvantages of the reptile respiratory system?

Answer 8

Advantages:
- Able to survive well on anaerobic respiration
- Lungs are easy to sample and drain if infected
Disadvantages:
- Enlargement of other organs in coelomic cavity or fluid accumulation may limit ability to ventilate

Question 9

Describe the alimentary system of reptiles

Answer 9

• Anatomy varies depending on diet
• Shorter than mammals and birds GIT transit time slow
• Have cloaca (rectum, reprodutive tract and urinary tract all empty here)
• Some reptiles have permanent teeth some shed them regulalrly
• Some have modified salivary glands that produce venom

Question 10

Describe the urinary system of reptiles

Answer 10

• Fewer nephrons
• No loop of henle
• No obvious defined cortex and medulla
• Cannot produce hypertonic urine
• Conserve water by low GFR with circulation maintained by renal portal system
• Not all reptiles have a bladder but water may be resorbed from here, distal colon and cloaca

Question 11

How does excretion of waste products occur in reptiles?

Answer 11

• No loop of henle = water conservation is vital
• Nitrogenous waste usually excreted as uric acid (requires less water for excretion)
• Species with more access to water excrete urea and species that live completley in water may excrete ammonia

Question 12

Describe the different methods of reptile reproduction

Answer 12

Some reptiles may lay aminote eggs
Others give birth to live young
Presence of a male is not always required and sex of offspring usually determined by external temperature of egg

Question 13

Tortoises, turtles etc.

What are features specific to chelonians

Answer 13

• Shell
• Carapace dorsally
• Plastron ventrally
• Sheel composed of dermal bones and other bones = problem is a orthapaedic problem

Question 14

What are some common features amphibians have in common with reptiles?

Answer 14

• Ectotherms (low metabolic rate)
• 3 chambered heart
• No diaphragm
• Simple GIT with teeth regularly shed
• Can excrete uric acid/urea/ammonia depending on species
• Have urinary bladder

Question 15

What are some unique features of amphibians?

Answer 15

• Most have aquatic larval forms in which gas exchange occurs in external gills
• Metamorphasis to adult form associated with lung development
• Lungs primitive so they also respire through their thin skin and skin also important for osmoregulation

Question 16

What is reproduction like in amphibians?

Answer 16

• Most lay eggs without a shell
• Eggs laid in damp places to avoid dessication
• Fertilisation internal or external
• Some species do not metamorphose
• Salamanders can regenerate limbs

Question 17

How do the features of amphibians transfer to clinical practice?

Answer 17

• Problems with water quality will have direct effcts on amphibians health
• Medications can be given in the water and will be directly absorbed
• Temperature of the water will affect drug metabolism

Question 18

What are some common features of fish?

Answer 18

• Ectotherms
• Thin glandular skin with scales for osmoregulation and minimal subcutaneous tissue
• Skin integrity important for osmoregulation - skin damage can be fatal
• Lateral line detects sound and pressure changes
• Kidneys have cranial haematopoietic and caudal excretory parts
• Swim bladder controls buoyancy
• GIT very variable depending on diet
• Liver and pancreas may be combined

Question 19

Describe the CVRS of fish

Answer 19

• Take oxygen from water
• Water passes into the mouth and out through the gills
• As water flows across the gills, oxygen diffuses into blood and carbon dioxide diffuses out via a countercurrent exchange mechanism
• Heart is 2 chambered (1 atria, 1 ventricle)