Anatomy of Reptiles. Amphibia and Fish
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How does an ectothermic animal control their body temperature?
They are reliant on external sources of heat to control their body temperature as they have limited heat production from their metabolism
What is the difference between poikilothermy and heliothermy?
Poikilothermy is when an animals body temperature varies with the temperature of the environment. Whereas heliothermy is when animals bask in the sun to increase their body temperature.
Which area of the brain controls thermoregulation?
Which gland in the brain detects light levels?
The pineal gland
What are the advantages/disadvantages to exothermic thermoregulation?
- Advantages - less energy waste in maintaining body temperature (ectotherms only use ~10% of the energy an equivalently sized mammal uses to maintain its body temperature)
- Disadvantages - activity is dependent on the ambient temperature. Poor aerobic capacity may limit endurance (most ecotherms are good at short bursts of activity but their stamina is poor)
How many chambers are there in a reptilian/amphibian heart? How does this arrangement help these species to reduce heat loss?
- Three (two atria with one common ventricle)
- It allows the lungs to be bypassed, reducing heat loss.
Describe the mechanisms involved in thermoregulation using the a) cardiovascular system b) peripheral vascular control, in reptiles, amphibia and fish
- a) Heart rate increases with temperature. Higher temperature > higher heart rate > higher possible activity levels
- b) Can use peripheral vasoconstriction and vasodilation to control their body temperature
State three examples of behaviours employed by ectotherms to alter their body temperature
- Altering pigmentation of the skin
- Shade seeking
What is UVA and UVB needed for?
- UVA triggers reproduction
- UVB is needed for vitamin D conversion
What are the three layers in the epidermis of reptile skin?
- Stratum germinatum
- Intermediate lipid-rich layer
- Stratum corneum
Where are most of the colour-generating cells located in reptile skin?
Between the dermis and epidermis
What is the term for shedding of the skin?
Which gland controls ecdysis?
The thyroid gland
Where does new skin develop from in reptiles?
The intermediate layer of the epidermis
What is failure to shed the skin known as?
What are the three functions of amphibian skin?
What affect would a drop in humidity have on an amphibian?
Any drop in humidity will affect their respiratory ability as their skin contains mucous glands which maintain moisture and are vital for respiratory function
What precautions must be taken when handling amphibians?
Gloves should be worn, as some species have lethal poison glands. Also the oils on your skin can disrupt their mucous layer and affect the animals respiratory function.
Why is healing much slower in reptiles than in mammals?
As they generally lack the Haversian bone system
What is the optimal Ca:P ratio for reptiles?
What disease is common in pet reptiles with incorrect husbandry (i.e. diets that lead to an incorrect Ca:P ratio)?
Metabolic bone disease
True or false: reptiles have nucleated red blood cells?
True or false: reptiles possess a diaphragm?
False - they exert negative pressure when breathing. When breathing reptiles undergo inspiration, expiration and relaxation/breath holding phases.
Why can anaesthetising reptiles via gas inhalation be challenging?
As the relaxation phases can last between 30mins-33 hours
How many chambers are there in a fish heart?
How does a fish heart differ from a mammalian heart?
A fish heart is a linear heart. Blood is pumped in a single series circuit: heart > gills > body > heart
Where does respiratory exchange mainly occur in fish?
Describe the structure of gills
There are typically two rows of thin lamellae projecting from each of the four brachial/gill arches. Gill rakers are essentially filters. Water flows out through the opercula.
What are the three ways that gas exchange occurs in adult amphibians?
Using simple paired lungs, buccopharyngeal or external cutaneous gas exchange
True or false: like reptiles, amphibians can create negative pressure?
False - they must force air in by contractions of their throat muscles
What is the cloaca?
This is a common exit for digestive and genitourinary systems
What are the three chambers that make up the cloaca?
- Copradeum (anterior chamber that collects faeces)
- Urodeum (middle chamber which the ureters and reproductive tract drain into)
- Proctodeum (caudal chamber which is the common path for excretion)
What other function does the cloaca have in some desert species?
It is a site of water reabsorption
List the different ways reptiles retain water
- They excrete uric acid rather than urine
- Cloacal reabsorption
- Reduced GFR
- Salt glands
- Renal portal system
Where are the kidneys located in reptiles? How do they differ from mammalian kidneys?
The caudal coelom. They do not contain the loop of Henle, renal pyramid or pelvis.
True or false: the bladder is found in all reptile species?
False - the bladder is only found in chelonians (turtle, terrapin and tortoise) and some lizards.
In species lacking a bladder where do the ureters open onto?
The ureters open directly onto the cloaca.
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