Sea Turtles Flashcards
Return to water
Out of >12000 extant reptile species, around 100 have re-entered the marine realm.
7 species of sea turtle, 80 species or sub of snake, marine iguana and other species in brackish waters.
All major reptile groups have a few members that enter marine habitats.
Challenges
Breathing, much easier to extract oxygen from air.
Locomotion, moving in water much more E efficient
Reproduction, large offspring, advantage of terrestrial juvenile habitat.
Osmotic balance, no advantages, multiple mechanisms for dealing with salt ingestion despite water tight skin.
Decompression, problems of decompression offset by advantages of air breathing.
Phylogeny
Species, hawksbill, loggerhead, green, flatback, Kemp’s Ridley, Olive Ridley, Leatherback.
Fossil record of turtles can be traced back to Upper Triassic
Earliest terrestrial fossils had fully developed shell.
First marine turtles appeared in the Jurassic.
By cretaceaous, 4 marine turtle families.
Occupy low to mid high latitudes, as far S as New Zealand and as far north as scandanavia.
Life history and reproduction
Females excavate with hind limbs for nest
Deposit clutch of up to 100 eggs
Temperature dependent sex determination
Hatching simultaneous at night
Nest environment
Incubation period goes down as temp increases, non linear.
Temp decreases with sand depth
Thermal tolerance 25-35
Tidal inundation reduces temp and oxygen levels in sand column
Sex determination
Extrinsic factors after fertilisation
Chance: Bonellia verdis, larvae float in ocean if they land on a female they become male.
Max number of offspring, plant parasite, if nutrients are sparse become male, if plentiful are female which enhances reproductive potential of the population.
Social: coral reef fish may start as one sex but later change to the other.
Temperature: Incubation temp during a brief but specific stage of embryogenesis.
Migration, tagging and tracking
Led to lots of new info on movements and behaviours.
Turtles are relatively large and powerful, surface regularly and have a conveniently bulky carapace to attach devices to.
Next step is satellite based tracking.
