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….. Highest Driest Windiest and Coldest continent on Earth! Animals in Antarctica have unique and special adaptations for survival 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 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 Jennifer Burns Michelle Shero This map shows the general range of the Weddell Seal, and the seasonal ice cover around Antarctica Image credit: Jennifer Burns Now for the adaptations… Remember the colors!: Anatomical Physiological 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! 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 milk is 60% fat! Human milk is 4%fat. Grams of Fat Consumed per Day 60 % Fat Content 50 6000 40 30 5000 20 10 4000 0 Human Milk Weddell milk 3000 Weddell seal babies consume 5400 grams of fat per day. That’s 48,600 calories! 2000 1000 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! 0 Human baby Weddell pup 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! 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! 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). 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 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 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! Hemoglobin range (red) 30 The Weddell seal’s blood is all about holding the most oxygen possible! 25 Hemoglobin, g/dl Plus, they have 30-50% more hemoglobin than human blood. Hemoglobin is the oxygen carrying protein in blood. 20 15 10 5 0 Human Weddell 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. 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. 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. 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 •Adapted to a habitat – the fast ice - that is hard for any predators to reach •Delayed implantation of up to 90 days after breeding. Fertilized eggs don’t start developing until January 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-scienceof-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.