Crocodilian Biodiversity Flashcards
1
Q
Give 2 Asian spp of Gavialidae
A
- Gharial - North India: large body, narrow snout, male has bulbous nasal appendage
- False Gharial - SE Asia: large body, narrow snout broadens towards base
2
Q
Describe Alligatoridae
A
- U-shaped snout
- upper teeth only visible
- head shorter and wider
3
Q
Describe crocodylidae
A
- v-shaped snout
- all teeth visible
- 4th tooth in lower jaws prominent
4
Q
Describe slender vs robust snouts
A
- ‘longirostrine’ jaws -> low drag, extra reach for small, agile aquatic prey
- ‘brevirostrine’ jaws -> high strength for large, hard terrestrial prey
5
Q
Describe an ambush predator’s head
A
- eyes, ears and nostrils raised above tip of snout
- nostrils and ears can be closed
6
Q
Describe crocodilian eyes
A
- iris: vertical slit by day, widens by night
- retina has reflective tapetum lucidum - night vision
- translucent nictitating membrane underwater
7
Q
Describe the crocodilian palatal flap
A
- plate of tissue at rear of oral cavity - closes pharynx against water entry
- can breathe with mouth open underwater
- air does not pass via mouth to reach trachea
8
Q
Describe ‘twist-feeding’
A
- lack specialization dentition for prey too large to be swallowed whole
- dismember by spinning
9
Q
Describe crocodilian digestion
A
- dilated stomach - principle site of digestion
- bone digested in 18days
- preferred body temps: before feeding 26 dc, post-meal 30
- ectotherms bask after meal
- CO2-rich blood ‘shunted’ to stomach after meal
10
Q
What is the direction of airflow in crocodilian lungs?
A
unidirectional airflow
11
Q
Describe crocodilian cloaca anatomy
A
- coprodaeum - faeces
- urodaeum - urine storage and post-renal modification
- proctodaeum - genitalia
12
Q
Describe nitrogen excretion in crocodilians
A
- distal rubule: active reabsorption of salts, secretion of HCO3- to neutralize NH4+
- nephrons lack loop of Henle - urine not concentrated
- freshwater: clear dilute NH4HCO3 urine
- hyperosmotic conditions leads to decreased volume of white uric acid
13
Q
How can a crocodilian be sexed?
A
- males generally larger
- phallus hidden inside cloaca in resting state: does not increase in size with blood entry, cloacal muscles rotate phallus out of opening
- potential confusion with smaller female clitoris
14
Q
Describe crocodilian mating
A
- large males dominant and territorial
- copulation: male curls tail under female, lying to side
15
Q
Describe the 2 oviducts in female crocodilians
A
- secretory activity peaks in reproductive season
- homologies to birds
- posterior uterus - calcareous eggshell
- anterior uterus - eggshell membranes
