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Figure 34.14 The origin of tetrapods
Return to the sea: Marine birds,
reptiles and pinnipeds
Phylum Chordata
Now we move to reptiles
(Class Reptilia) and birds
(Class Aves), then on to
marine mammals
(Mammalia). These are all
re-entry animals – they reentered the marine
environment to exploit
niches there. With birds
we see the advent of true
endothermy. We call most
of these organisms (as well
as the large fish) nekton
Nekton
• Free swimmers
• Tend to be large
• The birds, reptiles and mammals breathe air, and are
all re-entry animals
• They have various adaptations for thermoregulation,
breeding, osmoregulation, and movement that evolved
in response to their re-entry into an aquatic
environment
• MANY are K selected, which makes them susceptible
to exploitation, invasive species etc. • Genetic bottlenecks
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Nekton adaptations
Sea Turtles
•  r vrs. K selection reproductive strategies
•  Breeding on land – many still rely on land
(but not cetaceans and some others)
•  Migrations – often long
•  Staying warm (endotherms)
•  Osmoregulation (salt and water balance) – Salt glands in marine birds remove excess salt from the blood
LeatherBack
8 species, all threatened or endangered – all lay eggs on land
and depend on beaches for reproduction
Green Sea Turtle
Strong Swimmers who spend most of their
lives in the open water. Front flippers used
for swimming, back flippers used for
steering
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Illness
Sea Turtles
Papilloma virus is
affecting many sea turtles
(especially greens). We
don’t know why
Take a look at the SWOT
website:
http://seaturtlestatus.org/
Sea Turtles
Re-entered the sea about 150 MYA
Have a very long generation time and life span (in excess of 80 years)
Reproduce late (often not until they are 20-40 years old)
K selected!
They live throughout the tropics and suptropics
Can stay underwater up to 50 minutes!
They undertake extensive migrations from breeding to feeding areas
Females have breeding site fidelity
Sea Turtle diet
Depends on the species….
Many juveniles are omnivorous (eat algae, plants and other animals)
They are largely all carnivores and eat
•  Sponges - esp. Hawksbill turtles
•  Jellies and salps (leatherbacks)
•  Crabs
•  Fishes
•  Urchins
•  Gastropods
•  Cephalopods
•  Adult green turtles eat sea grasses and algae
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Food
Food
Leatherbacks eat jellyfish and other soft-bodied animals. A
floating plastic bag looks just like a jellyfish, but it will choke
a sea turtle. Leatherbacks eat jellyfish and other soft-bodied animals. A
floating plastic bag looks just like a jellyfish, but it will choke
a sea turtle. Loggerheads heat hard shelled organisms. Nesting and breeding:
Females nest every few years
once reproductive
They will return to the beach
where they were born approx.
every 2 weeks (up to 7 times)
during the breeding season to
lay up to 130 eggs
Green Turtle nesting sites
Males remain in the water –
mating happens there
Hatching happens after 9-10
weeks
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Eggs
Nesting
The female leatherback comes ashore to nest. She crawls up
at night, digs a hole in the sand, and lays 80 to 100 eggs. At
dawn, she returns to the sea. Hatching
The eggs hatch in about two months. Scientists can tell if
the hatchlings will be male or female by the temperature
of the nest. Colder temperatures produce males. Warmer
temperatures produce females. 22.5-27 deg C = males,
>30 def. C= females
The eggs look like billiard balls. Their shells are soft and
leathery. Scientists move nests that are too close to the water to
safer areas or to hatcheries
Hatching
Hatchlings wait until night to
leave the nest. Predators, like
sea gulls, would eat them
during the day. The new
hatchlings head for the water.
When they get there, they ride
out to the sea. 5
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Conservation
Poaching – food and products
CITES controlled – International treaties and some local regulations
TED devices
Light ordinances
Protected beaches
Controlled harvesting
Plastics!!
Habitat destriution: building on
beaches
Erosion and sea level rise
Other Marine Reptiles
Salt Water Crocodile
Size:
Where They Live:
What They Eat:
Special Facts:
Other Marine Reptiles
Sea Snakes
Other Marine Reptiles
Marine Iguana - Galapagos
Special salt
glands in the
nose for salt
excretion
length of crocodile- 5 to 15 feet.
coastal areas, tidal and nontidal near saltwater snails, frogs, fish turtles, snakes, waterfowl, small mammals the crocodile will swallow its prey whole. Crocodiles have been around since the dinosaurs
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Seabirds
Like the reptiles, pinnipends and cetaceans these are
re-entry animals - they went from land back into
the water. Why?
•  Sphenisciformes
•  Porcellariiformes
•  Charadriiformes
•  Anseriformes
•  Ciconiiformes
•  Pelicaniformes
Something about…seabirds
28 orders of birds (8600
species) - 4 ‘true’ orders
of seabirds
Approx. 250 species
•  All seabirds still breed on
land - many on islands
•  Many migrate long
distances
•  Many are threatened or
endangered
•  Many serve as harbingers
of ocean conditions
•  Endotherms (higher body
temperatures than us!)
Adaptations
•  Webbed feet
•  Countercurrent heat
exchangers
•  Oil in feathers (some)
•  Air in feathers (some)
•  Salt secreting glands
•  Variety of ‘lifestyles’
Seabird ‘lifestyles’
Seabird ‘lifestyles’
Shorebirds: ‘Waders’
Divers: ‘Pursuit divers’
•  Long legs (some)
•  Webbed feet
•  Specialized bills
•  Low oxygen consumption
•  Countercurrent heat exchangers in legs
•  ‘Fusiform’
•  Avocets, stilts, curlews, sanderlings, plovers
•  No oil in feathers
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•  Plunge divers
•  Skimmers and wanderers
•  Scavengers
•  Kleptoparasites!
Counter current heat exchangers revisited
• Blood in the arteries runs deep (not near the
surface)
• As it passes by cooler veins, it
gives up some of its heat, warming
up the veins. • In this way, heat can be ‘trapped’
within areas where it is needed
Seabirds stay warm:
•  By using
countercurrent heat
exchangers
•  By having air in their
feathers
•  Some have fat
(penguins!)
•  Some have oil in
feathers
•  High metabolism
Seabirds osmoregulate:
•  By having a salt
secreting gland (to get
rid of excess salt)
•  By producing uric acid
instead of urea (helps
retain water)
•  By having efficient
kidneys
•  They can drink
seawater!
Breeding on islands
•  Most seabirds breed on islands or in large
colonies
•  What are the conservation implications?
–  Introduced rats, cats on islands where birds are
ground nesters
–  Destruction of colony site = destruction of huge
percentage of the population
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Long migrations
•  Seabirds undertake some of the
longest migrations of any
animal: the arctic tern migrates
10,000 miles from the Arctic to
the Antarctic!
•  These migrations are to and
from feeding and breeding
grounds.
•  Seabirds are highly dependent
on oceanographic conditions
and food availability
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