Sensory Adaptations in Exotics

Question 1

Describe and explain the significance of infrared sensors in some snakes

Answer 1

Enable snakes to see in ‘infrared’ which assists with night vision, & hunting small, or very still prey

This ability allows them to detect prey & pinpoint where to strike

Plays a fundamental part of natural behaviour so in captivity an owner must be aware otherwise a snake may suffer from issues such as anorexia

Question 2

Name some snakes that uses infrared sensors

Answer 2

Pythons
Boas
Pit Vipers

Question 3

What is the vomeronasal organ and what is its importance?

Answer 3

Vomeronasal organ is important for activating the accessory olfactory organ.

This organ contains chemosensory stimuli which influence social or reproductive behaviour

Question 4

List the species that it is present in and briefly state how the anatomy varies across species

Answer 4

Present in many species:
Amphibians
Lizards
Snakes
Many over domestic
species
(not present in fish,
birds or chelonians)

Anatomy & location varies across species and may or may not include a connection to the mouth through the nasopalatine duct

Question 5

In knowing that snakes have a well developed vomeronasal organ, what is the significance of removing the tongue? Mention also the location of the organ

Answer 5

Organ is located on the roof of the oral cavity

Implications of tongue removal are…

Question 6

Describe the anatomy of reptile ears

Answer 6

External ear absent/diminished in most species
(except crocodiles)

Tympanum absent in some species
Where it is present it is superficial e.g. Flush with skin in reptiles

Question 7

What is the function of the anatomy of snake hearing?

Answer 7

No tympanic mebrane (not deaf)

Quadrate bone (takes place of ear drum)
- Jaw flexibilty
- Connects stapes (columella) to oval window of cochlea

Hear in low frequencies

Question 8

Describe the anatomy of birds ears

Answer 8

Outer, middle & Inner ear (like mammals)

Specialised feathers instead of pinna

Can have ear lobes (ornamental)
E.g. Chickens

Some birds have operculum
Accessory structure, aids sound location
Owls have this

X2 Tympanic membranes in songbirds
-second is made of smooth muscle - songbird can contract this to prevent
deafening themselves

Short external auditory meatus

Single auditory ossicle (like reptiles)

Question 9

What is the function of the anatomy of bird hearing?

Answer 9

2nd most important sense

Key for nocturnal birds

Homing pigeons- ability to sense magnetic forces to get home

Echolocation in some species
E.g. Cave swiftlets

Birds can regenerate their inner ear hair cells if damaged
Mammals suffer permanent hearing loss

Question 10

Describe the anatomy behind owl ears

Answer 10

Tightly packed rim of facial feathers (cf pinna)

Sound –> external auditory meatus

Left & right external auditory meatuses are different shapes
Helps localise sound

Question 11

What is the function of the anatomy of owl ears

Answer 11

Asymmetry enables precise pinpointing of prey

Intensity & timing of sounds

Horizontal and vertical planes

Question 12

Compare the inner ear of birds and reptiles to that of a mammalian ear

Answer 12

Simpler structure compared to mammals

	- One auditory ossicle (bone) 
		 columella (equivalent to stapes)

	- Cochlea duct is not coiled 
		Poor hearing

Question 13

Describe the anatomy of fish ears

Answer 13

An otolithic inner ear
Lateral Line:
Runs just below surface of the skin, along the sides of the body.
Covered by pored scales.

Question 14

What is the function of the anatomy of fish ears?

Answer 14

Fish are capable of detecting acoustic information through:

Lateral line is used to detect movement, vibration & pressure gradients in surrounding water
- Detect obstacles, swim in schools, predator avoidance

Question 15

How is vision under water different to vision in air?

Answer 15

Vision in Air
Strongly refracted through cornea
Corneal focus

Vision in Water
	Cornea/water have similar refractive index
		Lens focus

Question 16

Describe the anatomy of the fish eye

Answer 16

Huge variation between the species

Most can see colour (some see UV light)
	Rod:cone ratio varies depending on depth they live at
		
Main differences:	
		No lacrimal glands (tears)
		
		Rigid, immoveable iris (pupil are fixed size)
		
		Pupil fixed
		
		Lens:
			Spherical, protrudes through iris

Light focussed by changing position of lens in relation to retina

Question 17

Describe the anatomy of the avian eye

Answer 17

Eyes are relatively large in relation to the socket (exophthalmic)

	No tapetum lucidum 
	
	Avascular retina 
		Less light scatter from blood vessels, higher visual acuity 
	
	Pecten
		Highly vascularised, thin, highly folded
		Nutritive role (retina)?

Question 18

Describe avian vision

Answer 18

Colour vision varies among birds – some (not all) see colour

Many nocturnal birds also see UV light

Proportion of Diurnal birds: cones
Up to 80% in pigeon and chicken
Dim the lights to ease handling/catching

Nocturnal birds: rods

Question 19

What are some clinically relavent facts we need to remember about the avian eye?

Answer 19

• Note the normal appearance of pecten
  Do not confuse for retinal detachment or other pathology
  • Head trauma
    Common in birds of prey
    Remember – you must triage and provide first aid to all species
    If destroyed, euthanise

Question 20

Describe the anatomy of squamate eyes, including spectacles

Answer 20

Retina is avascular

\+/- papillary cone (lizards, some snakes)

Snakes and some lizards have spectacles

Question 21

Why is learning about spectacles clinically relavent?

Answer 21

Fused eyelids, transparent

Subspectacular space

Shed during ecdysis (colour change)

Dysecdysis:
Retained spectacles after shedding
Correct the husbandry
Rehydration = important
Bathe in warm water daily
Apply eye lubricant
Gently lift the spectacle off the eye using a wet cotton bud, from the very
edge of the eye.

	Surgery to remove the spectacle is rarely required but may be needed if sever.

	Never just pull skin off!

Question 22

Describe the anatomy of eyelids in reptiles and birds

Answer 22

Nictitating membrane
Present in reptiles
Very developed in birds
Striated muscles
Rapid sweeps, clean cornea

Lower lid
More mobile
Larger (birds)

Question 23

What is the function of Scleral Ossicles in reptiles and birds?

Answer 23

Bones within sclera

Protection and support

Aid function of ciliary muscles (visual accommodation)
Esp. night vision (nocturnal species)

Birds and reptiles

Question 24

What species have fovea present in the eye?

Answer 24

Present in birds, reptiles, fish & primates

Diurnal species (Especially raptors) have 2 fovea

Question 25

What is the function of fovea?

Answer 25

The high density of rods & cones provide a sharp vision and visual acuity.

Question 26

Describe the anatomy of the pineal gland

Answer 26

Endocrine gland, in brain

Most vertebrate species

Question 27

Describe the function of the pineal gland

Answer 27

Produces melatonin

Sleep/wake cycles 
	Responds to light/dark

Question 28

Describe the anatomy of the parietal eye

Answer 28

Many lizard (and amphibian) species

“3rd eye”, photoreceptive structure

Usually on top of head

Lens, cornea, retina

Question 29

Describe the function of Parietal Eye

Answer 29

Produces and secretes melatonin

Light/dark, sleep cycles, hormone production, thermoregulation

Question 30

Name and explain the test used to asses vision. What species can it not be used on and why?

Answer 30

Pupillary Light Reflex

In mammals, the pupillary light response (PLR) is used to assess vision.

Shining a light in the eye results in constriction of the pupil. 

Also affects contralateral eye - called consensual PLR. 

In birds and reptiles, the consensual PLR cannot be assessed – as both eyes are under independent control.

Question 31

What are mydriatics? What species can it not be used on and why?

Answer 31

In mammals, we can apply topical chemicals called mydriatics (e.g. atropine) to the eye to cause pupil dilation.

We cannot do this in birds and reptiles - the iris and ciliary muscles are skeletal muscle (not smooth)
-under voluntary control