Chelonian Anatomy and Physiology

What does chelonia mean?

it refers to the shelled reptile order

where do tortoise habitat?

in dry land terrestrial species (hot arid climates)

where do turtles habitat

marine

where do terrapin habitat

freshwater/brackish (slightly salty)

What is the size of a tortoise

10cm to 2.4m

what is the lifespan of a tortoise

10-200 years

what does heliothermic mean?

bask in sun to heat up

what does oviparous mean?

lays eggs, burys them - shows no maternal care

what will happen to chelonians to avoid extreme cold

brumate

what does crypodira mean?

hidden neck - flex vertebrae vertically

what does pleurodira mean?

side necked - flex vertebrae laterally

what families are cryptodira?

1. sea turtles

2. leatherback turtles

3. tortoises

4. softshell turtles

5. snapping turtles

6. pig nose turtles

what is responsible for the retraction of the head?

there are two strong muscles attached to the back of the chelonian skull, connecting it to the point of fusion of the cervical vertebrae with the shell

what is included in the pleurodira family?

mata mata, snake necked turtles

side neck turtles

(all pleurodira are freshwater aquatic species)

what is the shell structure composed of?

fused living dermal bone covered by keratinised epidermis

an upper section known as the carapace

a lower, flatter ventral section known as the plastron

what is the carapace and the plastron sections of the shell connected by?

either side, between the forelimb and hindlimb by the pillars of the shell

what is the carapace?

an endoskeleton, a fusion of dermal bone, ribs, thoracic and lumbar vertebrae

what is the structure of the carapace?

dermal bone plates - inner bony layers. Fusion of dermal bone, ribs, thoracic and lumbar vertebrae

Outer keratinised epidermis made of individual segments called scutes (scales)

5 central (vertebral) scutes

4 lateral (pleural/costal) scutes

Numerous marginal scutes

1 nuchal scute

what are scutes?

outer keratinised epidermis made of individual segments (scaes)

how many central (vertebral) scutes are there

5

how many lateral (pleural/costal) scutes are there

4

how many nuchal scutes are there

1

what is the plastron?

the ventral section of the shell

what is the plastron compromised of?

living dermal bone covered by keratinised epidermis

how many cervical vertebrae is there?

8

how many trunk vertebrae is there?

10

what do trunk vertebrae have?

a rib attachment which fuses to the dermal bone plates

what is the function of the pectoral and pelvic girdles?

adding strength

how are the pectoral/pelvic girdles attached to the pastron/carapace?

by pectoral and pelvic muscles

what is included in the pectoral girdle?

prescapular process, coracoid and scapula

what is the formation of the carpus and tarsus?

fused - this provides strength

what does the fused carpus and tarsus provide?

strength

what is the structure of the humerus and femur as compared to d/c?

short

how many claws do tortoises have on the hindlimb?

4

what is the structure of the skull?

small and sturdy with rigid upper and lower jaws, horny beak

what is the structure of the trachea?

complete cartilaginous rings

what is the trachea protected by?

the glottis

when is the glottis closed?

at rest

what is the function of the trachea?

bifurcates high into the neck into two bronchi which lead into a lung

what does the structure of the trachea allow?

breathing when head retracted

what is the location of the lungs?

lie dorsally along the inside carapace

what is the external structure of the lungs?

they are spongy and occupy a large volume in the body cavity

what is the internal structure of the lungs?

the internal surface consists of numerous faveoli, which serve as the site of gas exchange

what serves as the site of gas exchange in the lungs

faveoli

what is the function of faveoli?

they provide a more expansive respiratory surface allowing for steady oxygen diffusion even during periods of low activity or extended dives

what do they have to aid in inspiration/expiration instead of diaphragm?

strong trunk musces

what is respiration aided by

movement of limbs/neck

muscles

how is respiration aided by the limbs and neck?

act to pump air into and out of the confined lungs

how are the lungs separated from the rest of the viscera

muscles

what is the stimulus for respiration

a fall in blood partial to oxygen

how is inspiration achieved?

by increasing the lung volume which causes a decrease in lung air pressure and as a result air is sucked in

how is expiration achieved?

limbs are retracted into the shell, causing an increase in soft tissue and pressure within the coelomic cavity which forces air out the lungs

what is aquatic species respiration aided by?

the pressure of water which can draw in and out the lungs

what do aquatic species have?

1. large oxygen stores

2. reduced metabolic rate

3. anaerobic respiration

4. cloacal respiration

structure of the tongue

fleshy and tightly attached

structure of the stomach

spindle shaped and simple

what is the structure of the heart?

three chambers; two atria and one common ventricle

where are the kidneys located

caudally and tightly adhered to the ventral surface of inside the carapace

where do the ureters empty into?

urogenital sinus (urodeum) which is connected to the bladder

what is the structure of the bladder

large bilobed structure with thin walls

what is the function of the bladder

reabsorption of water

Acts as a buoyancy and can reabsorb sodium

where does the penis lie

in the ventral aspect of the cloaca at rest, when engorge it is projected via the vent and curves cranially

how long can fertile eggs be carried for

4 weeks to 4 years

what is sexual maturity linked to

size

defence mechanisms

hinged body plates of their shell