and its amazing adaptations to a very extreme environment The Weddell Seal This is a Weddell seal pup. Notice how furry it is – we will come back to that concept later! and its amazing adaptations to a very extreme environment Photo by Steven Profaizer

Antarctica is a place of extremes It is the….. Highest Driest Windiest and Coldest continent on Earth!

Animals in Antarctica have unique and special adaptations for survival It could be mentioned here that all of the animals in Antarctica are marine animals. The source of food for all the life there is the ocean. Rebecca Shoop Robyn Waserman 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 This is a good opportunity to learn these terms, which will come up repeatedly in biology.

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! The temperature of the water ranges from -1.8C to 4°C (27.8˚F – 39.2˚F) during the year. Above the ice, winter temperatures can be from -26˚C to -8˚C (-16˚F – 16˚F), with added wind chill. The water is much warmer! However, the seals come out to bask in the constant summer sun and have their pups. The sun also helps their fur to molt, so they can grow a new coat in time for winter.

Weddell Seals (Leptonychotes weddellii) Daniel Costa Jennifer Burns Aren’t they cute?! Since they have no predators, they tend to be quite unafraid of humans, and don’t mind people getting very close. Michelle Shero

This map shows the general range of the Weddell Seal, and the seasonal ice cover around Antarctica Why is the Weddell Seal the most southerly mammal? What about the other seals? Because the other seals that live in Antarctica live on pack ice, which is ice that is found in the open water, and drifts with the currents. Pack ice is found farther north, not attached to the continent as fast ice is. Image credit: Jennifer Burns

Now for the adaptations… Remember the colors!: Anatomical Physiological Behavioral How do Weddell seals stay warm in such a cold environment? Blubber vs. Fur Basking in the sun Very rich milk Unique Nose structure

Obesity problem? Or perfect adaptation? 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! Blubber has a double purpose: it is used to keep the Weddell seal warm, and it is also used for energy! During the long winter months, the seals are foraging constantly, building up their blubber layer. During the summer, it takes a lot of energy for the females to feed their pups. It takes even more energy for all the seals to molt and grow new fur. The moms lose about 110 lbs of blubber in the first few weeks of a pup’s life, to make milk to feed the youngster. 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! All seals are in the order Pinnipedia. They are called Pinnipeds! Weddell seals are “true seals”, order Phocidae. Fur seals and sea lions are in the order Otariidae. One big difference between them is the fur! Weddell seal fur is made of short, shiny guard hairs, and is used for protection more than insulation. Pups, on the other hand, are born with soft, downy fur called lanugo that keeps them warm. Human babies are born with fuzzy lanugo also! The pups are born without much blubber, and as they gain it, they will lose this long, fuzzy fur, and grow the short, straight fur of the adult seal. Remember this picture from the first slide? A seal pup showing off his fuzzy fur coat.

Weddell seal milk – pure fat! Weddell seal milk is 60% fat! Human milk is 4%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 seals gain 150 pounds in the first few weeks of life!

Notice how form and function work together! A very special nose! 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 air in a process called counter-current heat exchange Notice how form and function work together! In humans, the nasal turbinates help to warm and moisten the air, but the process is not nearly as efficient as in seals. Humans can lose a lot of body heat through the nose. In seals, both the warming and moistening of incoming air and the recapture of heat and moisture from exhaled air is extremely efficient. An elephant seal can recover over 70% of the moisture that was added to incoming air. Considering how cold and dry the air in the polar regions, especially Antarctica, this is a very important adaptation! Grey seal nasal cavity. Photo credit: Jennifer Burns Seal vs. human nasal turbinates. The seal turbinates are far more numerous and convoluted!

How do Weddell seals get around in the dark of winter under the ice? Long whiskers Huge eyes Special teeth Daniel 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 Chris Burns 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! The large iris allows maximum light absorption. When underwater where it is dark, the seals pupils, which are barely visible on land, become large and round. This, combined with the tapetum, maximizes the amount of light that is reflected onto the retina. In the retina, there is a large number of rods, ready to absorb the light. Many nocturnal and crepuscular animals have the tapetum lucidum. Humans do not have it. Could this be the next new eye surgery – adding a reflective layer to enhance night vision? Seals do not have tear ducts, which is why their eyes water when they are on land. Eye shine in nocturnal animals is caused by the tapeta

More Focus on Eyes – the lens The cornea loses 87% of its refractive power in water! The light is then focused behind the retina, resulting in hyperopia (far-sightedness). 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). In humans, since the refractive power of the cornea is severely reduced in water, the ciliary muscles in the eye try to accommodate, and cause the lens to become a little more round. However, the maximum accommodation in an adult eye is about 25%, and this is reduced to almost 0% by age 60. This is why a diving mask helps us to see under water; the medium that the light is coming through as it contacts the cornea is what we are familiar with – air! When a seal is on land, the spherical lens causes the light to bend too much, resulting in the light focusing in front of the retina, rather than on it. The seal is myopic, or near-sighted on land. If you wear glasses, the corrective lenses simply bend the light in a way that it focuses on the retina, not in front or behind it. Do you think, if you are near-sighted on land, then perhaps you would actually see a little better in the water? What if you are far-sighted?

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 Whiskers in Weddell seals are sampled for study, as much can be learned about their diet during the past year by analyzing whiskers. Other nocturnal mammals have long whiskers – the most obvious example is the cat. Take a look at your cat’s whiskers and notice what a dominant feature they are! Whiskers can be relaxed (on land) or stiff and erect when they sense movement. This video shows some very alert whiskers! Can you think of another animal that has large whiskers? Is this animal nocturnal?

Chew on this – special teeth! 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 Daniel Costa Incisors Weddell seal teeth are truly remarkable. The fact that they can open their mouth so wide not only allows them to catch large fish, but it allows them to ream the ice efficiently to keep their breathing hole open. The way the incisors stick out aids in the very important need to maintain access to air! Notice that the behavior description is in red – another example of form and function working together. The jaw and tooth structure enables the behavior. Canines Photos by Jennifer Burns This video shows how the Weddell seal uses its teeth to keep the breathing hole open

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

It’s a bloody seal! 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. Weddell seals have a high volume of blood – 20% of body volume! Weddell seal blood is being compared to human blood in this slide for a point of reference. All three of these adaptations together add up to a massive oxygen storing capacity in seal blood. This enables the seal to remain active underwater for long periods of time without needing to come up for air. It is quite a remarkable physiological system! When you cut yourself, you know that your blood is not a thin liquid. Seal blood is much more viscous (thick) than human blood because of the large proportion of red blood cells. This makes it harder for the heart to pump all that blood, and the heart is a muscle that needs oxygen too! The seal handles this challenge by storing blood in the spleen and in a “sinus” in the liver. When the seal dives, this blood is made available to the heart and brain which need the extra oxygen. Plus, they have 30-50% more hemoglobin than human blood. Hemoglobin is the oxygen carrying protein in blood. 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. The color of an animal’s muscle indicates the activity the animal does. Darker muscle (more myoglobin) contains more “fast-twitch” muscle fibers. They are built for long and sustained activity, such as standing, walking, running, or swimming. Lighter muscles (less myoglobin) contain more “slow twitch” muscle fibers. They are made for quick bursts of activity, such as fleeing from a predator. Fast-twitch muscles get their energy from glycogen, which is a form of carbohydrate stored in muscles. You might wonder why some fish have meat that is so white, while others are darker. Consider the white fish: cod, haddock, flounder, halibut. These fish don’t move a lot. Their food is often near the bottom, and is not swimming away from them constantly. Think about some darker fish, such as tuna or salmon, that swim for long distances and need sustained power. Also compare the meat of different parts of a chicken (dark meat vs. white meat). What are the functions of each of these muscles? How about human muscle? What does it suggest we are good at? Michelle Shero 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

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! The alveolar sac and lobule collapse when the seal dives. Consider how long you can swim underwater before you feel the need for air! The longest Weddell seal dive has been recorded at 89 minutes, but a normal dive is about 20 minutes. They can dive as deep as 800 meters, but prefer to dive no deeper than 300 meters. A seal’s lung. Image credit: Kooyman GL (1973) Respiratory adaptations in marine animals. American Zoologist 13: 457–468 A seal depends entirely on oxygen stored in the muscles and blood to carry it through the dive!

More amazing oxygen info Weddell seal Notice the remarkable numbers in the Weddell seal! Image credit: Kooyman GL (1989) Diverse Divers: Physiology and Behaviour. Berlin: Springer. When we humans dive into the water, we take a deep breath first, and hold it. This works for us, because the lungs provide a lot of oxygen to our muscles while under water. It is also what doesn’t allow us to dive deep. Scuba divers need to use weights to go deep. Since the seal stores so much oxygen in its muscles and blood, the lungs can collapse and be useless during the dive, allowing greater depth. Notice the difference between the true seals (Weddell) and the fur seals and sea lions in the percent of oxygen stored in the lungs and blood when diving. 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. 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.

More interesting adaptations to the extreme climate Bask in the sun in summer, saving energy for pupping, breeding, and molting Pups grow fast, are weaned at 6-7 weeks (when the fast ice breaks up), and are on their own 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 In order for the embryo to start developing, it has to be implanted in the uterine wall. With delayed implantation, the embryo is held in a state of dormancy. There is still much to be learned about how animals do this, and what conditions maintain or end the “embryonic diapause,” or dormancy. There are approximately 100 mammals that have delayed implantation. The reproductive advantage is obvious, as the timing of breeding, gestation, and birth can be best suited for environmental conditions. In the seals, breeding takes place as the pups are being weaned, when the female ovulates. If gestation started immediately, the pups would be born just over 10 months later in the cold of winter. Reproduction has an extremely high energy cost, and delayed implantation is a remarkable adaptation! Terrie Williams Have strong nostril muscles that snap shut when diving Fusiform (torpedo) shape makes for very efficient swimming Steve Rupp

The End! Alex Eiliers

References http://scubageek.com/articles/wwwvis.html http://antarctica.ucsc.edu/home.html http://photolibrary.usap.gov/ http://www.arkive.org/weddell-seal/leptonychotes-weddellii/video-10.html http://www.dosits.org/ http://www.antarctica2000.net/wildlife/weddell.html http://www.annualreviews.org/doi/abs/10.1146/annurev.physiol.62.1.353 http://www.polartrec.com/resources/event/jennifer-burns-and-the-life-science-of-weddell-seals http://www.polartrec.com/ http://www.polartrec.com/expeditions/weddell-seals-in-the-ross-sea Thanks to: Alex Eilers, PolarTREC teacher Dr. Jennifer Burns, University of Alaska, Anchorage Sarah Crowley and Janet Warburton, Arctic Research Consortium of the U.S.