Download PRINCIPLES OF BIOLOGY: LECTURES 3 and 4

Marine Biology: June 6, 2007
Epipelagic Zone: General/Antarctic marine ecosystem
I.
Focus on penguins of the Antarctic Peninsula
A.
Three major species (Adelie, chinstrap and gentoo): We will focus on the Adelie
penguins.
B.
Adaptations for diving
1.
Solid bones (no air spaces as in flying birds = non-pneumatic)
2.
Hindlimbs
a)
Swung far rearward to serve as a rudder
b)
Webbed, of course!
c)
Sharp toes for gripping ice
3.
Forelimbs are modified into flippers
4.
Air sacs minimized to reduce buoyancy
5.
Feathers
a)
Covered with three layers of scale-like short feathers

Trap air for warmth (on land)

No flight feathers…
b)
Squeeze air out of feathers prior to a dive

See a stream of bubbles!
6.
Larger species are deeper divers:
a)
Less metabolic demand/gram of body tissue (so can hold breath longer)
b)
Larger wings mean more absolute movement forward
C.
Warmth
1.
Blubber
2.
Air in feathers (on land only)
3.
Special oils
D.
Breeding behavior of Adelie Penguins (Penguin taxon advisory group)
1.
Nest in large colonies of up to half a million birds on nearshore islands close
to the Antarctic continent. Nests are small depressions lined with pebbles
that are carefully selected (smooth, of correct size) and brought to the nest
site.
2.
Nests are started by males at the beginning of the season (they arrive at the
breeding sites first) and then added to by both birds after the pair is formed.
a)
Adelies are faithful to site and (often) to their mate.
3.
Usually two eggs are laid.
4.
Both male and female parent share incubation and chick rearing duties.
a)
The parents first alternate when the chicks are small, but after chicks
are larger both parents are needed to feed the chicks in order for them
to successfully fledge. The chicks are left alone in crèches where they
huddle for warmth and for protection against predators.
5.
The young must eat a diet comprised primarily/solely of krill.
a)
Adults can survive on fish, but not the young.
b)
Krill are high in necessary lipids that the chicks need to grow.
c)
Adults grab krill within schools individually in their beaks when they
feed.
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6.
II.
III.
The chicks are ready to fledge about 2 months after hatching.
a)
Nests that get started late in the season are unlikely to be successful
E.
Declines/shifts in penguin populations
1.
More northern colonies are being abandoned (see work of Stephen Emslie)
and the center of the population is shifting southward (work of Bill Fraser)
a)
In five colonies near Palmer Station, numbers of breeding pairs have
dropped from 15,200 to 9,200 in 25 years, while some smaller
colonies have disappeared altogether.
b)
Again, thought to be linked to the reduction in sea ice  reduction of
krill populations.
c)
Increased snowfall is also a cause of increased penguin mortality in
regions with low ice.

Moisture usually locked up in the ice is instead in the
atmosphere and falls as snow. The penguins build nests on the
snow, but when the snow melts, the nests are inundated by
water.
d)
In regions further south, Adelie penguin colonies are actually
increasing in size.
Non-penguin seabirds: many species, including…
A.
Blackbrowed albatross (and other albatross species)
1.
Can forage over thousands of kilometers; primarily feed on krill
2.
Surface and near-surface feeders
B.
Southern giant petrel
1.
Young can fend for themselves: gacking
2.
Primarily feed on krill
C.
Wilson’s storm petrels
1.
“Jesus birds”: feed on near-surface zooplankton (smaller krill species,
copepods, amphipods)
D.
Blue-eyed shags
1.
Feed on fish and squid; deep divers
2.
Have heavy bones like penguins.
Order Pinnipedia: Seals, sea lions and walruses (but no walruses in the Antarctic)
A.
Family Phocidae: true (earless) seals
1.
Phocid characteristics
a)
no external ear
b)
short foreflippers
c)
hindlimbs held parallel, work together for propulsion
d)
relatively short neck (although still much more than a cetacean, which have
highly compressed and fused cervical vertebrae)
2.
Antarctic species
a)
Crabeater seals

>90% of diet is krill (mostly E. superba)

Specialized tricuspids with small spaces for straining krill
b)
Elephant seals

Squid (and fish) eaters
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

IV.
Large breeding colonies
Sexual dimorphism; highly skewed reproductive success in
males.

Distinct species from the Northern elephant seal populations
c)
Leopard seal

Only phocid that eats seabirds and other seals

Also feeds on krill (specialized dentition in lateral teeth is
similar to crabeater seals)
d)
Weddell seals

Feed on fish and squid

Well-studied for their deep diving physiology and behavior
e)
Ross Seals (relatively rare)
B. Family Otariidae: sea lions, fur seals
1.
Otariid characteristics
a)
small external ear
b)
long foreflippers used for standing (on land), and for propulsion
c)
hindlimbs can be splayed apart, turned under body for support on land
d)
Sex organs retractable; testes external
e)
Flexible neck: predation
2.
Antarctic species
a)
Antarctic fur seal; Subantarctic fur seal

Feed on…krill, fish, squid and penguins
C. Family Odobenidae: walruses: 1 species, circumpolar (N. Pacific and N. Atlantic
subspecies; no Antarctic species)
1.
No Antarctic species, so won’t go into… except for this poem…
Order Cetacea
A.
Suborder Mysticeti: the baleen whales. Antarctic Mysticeti were greatly reduced
in numbers during the late 19th and early 20th century.
1.
Major characteristics
a)
Baleen plates for filter-feeding
b)
Most common Antarctic species use a method called compressionfiltration (just like the krill they eat!)
B.
Key species of Antarctic Mysticeti
1.
Humpback whales
a)
Distinctive throat grooves allowing for enormous throat expansion during
feeding

Feed primarily on krill in the Southern ocean

Use a technique called “bubble-netting”
b)
Migration: cold waters to tropics
2.
Minke whales
a)
Small
b)
Most abundant of the baleen whales, with higher reproductive rates
c)
Throat grooves and similar feeding mechanisms as the humpback whales

Feed on…krill!
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3.
V.
Blue whale
a)
Distribution: Once worldwide, now the largest populations are found off
coastal California

Migrate to tropical waters for calving

Appear to avoid coastlines, so they are difficult to track
b)
Largest animal ever (note: you don’t have to memorize these stats!)

Can be up to 24.5 meters (female)

Mouth alone of 6 meters

Max weight: 190 tons

Heart the size of a VW bug

Spray from blow is about 6 meters high.

Larger prior to mechanized whaling

Only hunted after the development of the grenade harpoon in
the 19th century.

In one year, 30,000 were killed (not sure which year)

Loudest and deepest voice of any animal (180 dB, 10 Hz)
c)
Diet is almost exclusively…KRILL! (Yep, you do have to know this!)
Suborder Odontoceti: toothed whales
A.
Antarctic species = Orcas!
1.
Prey on all the seal species
a)
commonly eat crabeater seals due to their high abundance
b)
Will even eat leopard seals
2.
Prey on whales
a)
Probably once a more important food resource
3.
May prey on penguins
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