Amphibian, reptile and fish GIT anatomy

what is the quadrate bone the same as in mammals?

• the incus

how are snake jaws adapted?

• no mandibular symphysis

• quadrate bone

what are the 2 types of lizard teeth?

• acrodont

• pleurodont

what are acrodont teeth

• reptile teeth where the attachment is the crest of the bone

• they’re rarely replaced if lost

what are pleurodont teeth

• reptile teeth that are attached by labial wall

• shed and replaced

Outline snake teeth

• pleurodont

• 3 rows

• point backwards

• only differences in fangs

what are the 3 rows of snake teeth?

• maxiallry

• pterygoid + palatine

• mandibular

what are 3 uses of venom

• feeding

• predation

• defence

what are the classes of snake venom

1. rear or front fang

• front fang → constantly erect or folded

outline chelonian ‘teeth’

• they don’t have teeth!

• they have a sharp, keratinised beak

compare the beak structure of a herbivorous chelonian to a carnivorous one

• herbivorous have hard ridges in hard palate

• carnivorous have sharp beak + external adductor muscle

outline the tongue of snakes

• in sheath under glottis

• highly mobile, forked

• jacobson’s organ

Outline the tongue oflizards

• mobile

• fleshy or keratinised

• jacobson’s organ for olfaction

what is the difference between fleshy and keratinised tongues (in terms of taste buds)

• fleshy have more taste buds than keratinised

Jacobson’s organ:

1. what is it

2. where is it

3. what nerve

4. in which species is it best developed?

1. paired accessory olfactory organ

2. oral cavity roof

3. vomeronasal nerve

4. snakes

describe the glottis of snakes

• floor or oral cavity but rostral

• highly moveable

describe the location of the glottis of lizards

• base of tongue

describe the location of the chelonian tongue

• base of tongue

what are 3 uses of reptile oesophagus?

• transporting food

• storage

• digestion

what is the role of the pancreas within these different species?

• variable pancreatic enzyme secretion

  • chitinase produced if insect eating

what is something to note of the snake stomach?

• less well defined cardiac sphincter

how does the length of intestines vary in different reptilian species?

• herbivore > omnivore > carnivore

in which species is the caecum present?

• herbivorous chelonians, lizards

describe the colon in reptile speciess

• herbivore > carnivore

• heavily convoluted in areas to increase time for microbial fermentation

outline the role of the microflora in herbivorous species

• longer GIT

• cellulose → VFAs by fermentation

what do young herbivorous reptiles need to help microflora development

• inoculum of adult faeces

what types of organisms do we expect in a reptile microflora?

• aerobic and anaerobic bactreria

• gram -ve

• gram +ve

• yeast

• pr

what is key for rate of digestio

• body temp

how does the transit time of digestion compare in reptiles to mammals?

• slower

what are 3 sensory methods for food detection

• visual

• chemosensory

• thermal

what is involved in chemosensory detection of food?

• olfaction

• vomerolfaction

• gustation

what species use thermal detectio of food

• boidae

• pythonidae

• viperidae

how does thermal food detection work?

• heat pits detect temp of prey

• visual centres overlay this info to create real time thermal vision

describe the teeth of crocodiles

• thecodont - no periodontal ligament

• replaced around every 2 years

describe tuatara teeth

• maxillary and pterygoid+palatine

how are slow worms developed?

• good vision

• eyelids (as are lizards)

• ovovivaparous

how are amphisbaenians developed?

• limbless

• small eyes/blind

• excellent hearing

describe gymnophiona amphibian

• legless

• small/no eyes

• burrowers

how does the diet choice of amphibians change over time/

• larvae are often herbivorous

• adults are all carnivores

what limits an amphibian prey choice

• size

describe frog + salamander tongues

• long

• muscular

• sticky end

• variable attachment point

amphibian teeth:

• main role is?

• replace/shed how frequently?

1. hold/keep prey in mouth

2. shed and replaced throughout life

describe the role fo the SI and LI in amphibians

• SI = enzymatic digestion

  • LI = water and salt absorption

what is unique about salamander LI/SI?

• no valve between them

Fish mouths:

1. why do they vary

2. salivary glands present?

3. teeth?

4. role of gill rakers?

1. diet

2. none

3. pharyngeal ones in some species

4. retain food and prevent them entering the gills

do all fish species have a stomach?

• no 15% are agastric, they have an intestinal bulb instead

what adaption of the proximal intestine are there?

• presence and number of pyloric caeca/appendices or sacs

how does intestinal length vary in fish species?

• herbivorous » carnivorous

do fish have a define pancreas?

• no, very diffuse

what is the swim bladder

• an outgrowth of the foregut

• role in hydrostatic equilibrium and sound production

what are the 2 types of swim bladder

1. physostomous

2. physoclistous

what is a physostome swim bladder?

• a swim bladder with a pneumatic duct and still connected to the oesophagus

what is a physoclistous swim bladder?

• swim bladder with rete mirabile rather than connection to oesophagus