The Weddell Seal

and its amazing adaptations to a very extreme environment

Photo by Steven Profaizer

Antarctica is a place of extremes

It is the…..

HighestDriestWindiestand Coldest

continent on Earth!

Animals in Antarctica have unique and special adaptations for survival

Robyn Waserman

Rebecca Shoop

Steve Rupp

3 Types of Adaptations

Anatomical Adaptations (will be purple)- have to do with structure

Physiological Adaptations (green)- have to do with function

Behavioral Adaptations (red)- have to do with action or activity

A little about the Weddell Seal

• The most southerly dwelling mammal on Earth• Live on fast ice, floating ice that is attached to

land. Enter the water through cracks in the ice• Spend most of the year in the water, coming

out in the summer (Nov-Jan) for pupping, breeding and molting (and soaking up sun!)

• Can dive for over an hour, and up to 600 meters deep!

Weddell Seals (Leptonychotes weddellii)

Daniel Costa

Michelle Shero

Jennifer Burns

This map shows the general range of the Weddell Seal, and the seasonal ice cover around Antarctica

Image credit: Jennifer Burns

How do Weddell seals stay warm in such a cold environment?

Now for the adaptations…

Remember the colors!: Anatomical Physiological Behavioral

•Blubber vs. Fur•Basking in the sun•Very rich milk•Unique Nose structure

Blubber is warmer than fur!

How much blubber are we talking?

30-40% of body weight is blubber. That means, up to 240 kg, or 528 lbs in the largest seals, is pure blubber! Over 2 inches thick!

Obesity problem? Or perfect adaptation?

Image credit: Michelle Shero, 'Weddell Seal Body Composition'.

But what is the fur for?

Weddell seals, unlike fur seals and sea lions, do not have a thick layer of fur. Blubber is warmer! Fur is more for protection than insulation.

Pups, however, are born with a soft, downy fur coat, which keeps them warm while they build up blubber from Mama’s milk!

Remember this picture from the first slide? A seal pup showing off his fuzzy fur coat.

Weddell seal milk – pure fat!

Weddell seal babies consume 5400 grams of fat per day. That’s 48,600 calories!

Breastfed human babies consume 40 grams of fat per day. That’s only 360 calories!

Weddell seal milk is 60% fat! Human milk is 4%fat.

Weddell seals gain 150 pounds in the first few weeks of life!

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A very special nose!

Seal vs. human nasal turbinates. The seal turbinates are far more numerous and convoluted!

Nasal turbinates are thin bones that divide the nasal passage. They are lined with nasal epithelia which is loaded with capillaries. Their functions are to

•Warm and moisten incoming air•Prevent heat and moisture loss in outgoing airin a process called counter-current heat exchange

Notice how form and

function work together!

Grey seal nasal cavity. Photo credit: Jennifer Burns

How do Weddell seals get around in the dark of winter under the ice?

Huge eyesLong whiskers

Special teethDaniel Costa

It’s dark down here!

Photo by Steve Rupp

A Focus on Eyes•Very large iris – the part of the eye that gathers light. Notice there is no visible white on the seal’s eye.•Large number of rods, photoreceptors that allow vision in poor light

•Protective mucus covers the eye surface

The tapetum lucidum is a reflective layer behind the retina that reflects light back to the retina for a second go around and more light absorption!

Eye shine in nocturnal animals is caused by the tapeta

Chris Burns

More Focus on Eyes – the lens

Seals make up for this with a very round lens, which bends the light more than the flat lens that humans have. This gives the seal good vision under water. On land, they are myopic (near-sighted).

The cornea loses 87% of its refractive power in water! The light is then focused behind the retina, resulting in hyperopia (far-sightedness).

Wild Whiskers!Also called vibrissae, whiskers have two functions:• To help find food• To help navigate

Special features of whiskers:• Each vibrissa can move independently• They have many sensitive nerve fibers

to detect water movement from passing prey

• Whiskers are shed periodically, and new ones grow

Can you think of another animal that has large whiskers? Is this animal nocturnal?

Whiskers can be relaxed (on land) or stiff and erect when they sense movement. This video shows some very alert whiskers!

Chew on this – special teeth!

Incisors

Canines

•Weddell seals can open their mouth very wide.•There are large canines, typical of carnivores•The incisors jut forward for a special purpose – to keep the breathing hole open

This video shows how the Weddell seal uses its teeth to keep the breathing hole open

Photos by Jennifer Burns

Daniel Costa

Noisy seals!•Weddell seals make some of the most bizarre and interesting sounds of all marine mammals. •Sounds are used for social interaction, territorial displays, and aggression•They have a very wide frequency range of sound •Males are more vocal, to attract females and display territory to other males•Sounds are made both above and below the ice

Click on any of these buttons to listen to some of their sounds Just for fun, listen to these

mothers and pups

How do Weddell seals dive so deep and for so long?

•Blood stores a lot of oxygen•Muscle stores a lot of oxygen•Collapsible lungs for diving deep

Remember, Weddell seals can dive for over an hour, and go as deep as 600 meters!

Their dives can range 5km from their breathing hole!

It’s a bloody seal!

Weddell seals have a high volume of blood – 20% of body volume!

They have a very high hematocrit of 50-70% – that is the % volume of blood that is red blood cells. This is caused by very large blood cells.

Plus, they have 30-50% more hemoglobin than human blood. Hemoglobin is the oxygen carrying protein in blood.

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Hemoglobin range (red)

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The Weddell seal’s blood is all about holding the most oxygen possible!

Mighty muscle myoglobin

What is the difference between hemoglobin and myoglobin? --They are both similar molecules that carry oxygen--

Heme = blood, myo = muscle, globin – the name of the protein portion of the molecules. Myoglobin is the oxygen carrying

protein in muscles.

From left to right: white fish, chicken breast, cow muscle, Weddell seal muscle. The darker the muscle, the more oxygen it can carry, which means it can sustain more activity for a longer period of time. Enough said!

Remember the adaptation color code: anatomical, physiological, behavioral

Michelle Shero

A flexible chest and collapsible lungs

The oxygen storing capacity of the blood and muscles are important in supporting the seal during deep dives, because…..the chest cavity of Weddell seals collapses when diving, and the air within them compresses. No oxygen exchange happens in the lungs during a dive!

A seal’s lung. Image credit: Kooyman GL (1973) Respiratory adaptations in marine animals. American Zoologist 13: 457–468

The alveolar sac and lobule collapse when the seal dives.

A seal depends entirely on oxygen stored in the muscles and blood to carry it through the dive!

More amazing oxygen info

Oxygen stores of dolphins, sea lions and fur seals, true seals, humans and penguins. The numbers in parentheses are the percent of oxygen stored in the lung, blood and muscle.

Weddell seal

Notice the remarkable numbers in the Weddell seal!

Before diving, the Weddell seal takes several huge breaths of air, to saturate the blood and muscles with oxygen. Then they exhale all the air, so the lungs can collapse more easily.

Image credit: Kooyman GL (1989) Diverse Divers: Physiology and Behaviour. Berlin: Springer.

More interesting adaptations to the extreme climate

•Bask in the sun in summer, saving energy for pupping, breeding, and molting

•Delayed implantation of up to 90 days after breeding. Fertilized eggs don’t start developing until January

•Adapted to a habitat – the fast ice - that is hard for any predators to reach

•Pups grow fast, are weaned at 6-7 weeks (when the fast ice breaks up), and are on their own

•Have strong nostril muscles that snap shut when diving

•Fusiform (torpedo) shape makes for very efficient swimming

Steve Rupp

Terrie Williams

Alex Eiliers

The End!

References

http://scubageek.com/articles/wwwvis.htmlhttp://antarctica.ucsc.edu/home.htmlhttp://photolibrary.usap.gov/http://www.arkive.org/weddell-seal/leptonychotes-weddellii/video-10.htmlhttp://www.dosits.org/http://www.antarctica2000.net/wildlife/weddell.htmlhttp://www.annualreviews.org/doi/abs/10.1146/annurev.physiol.62.1.353http://www.polartrec.com/resources/event/jennifer-burns-and-the-life-science-of-weddell-sealshttp://www.polartrec.com/http://www.polartrec.com/expeditions/weddell-seals-in-the-ross-sea

Thanks to: Alex Eilers, PolarTREC teacherDr. Jennifer Burns, University of Alaska, AnchorageSarah Crowley and Janet Warburton, Arctic Research Consortium of the U.S.