Blubber

Whale blubber.

Blubber is a thick, dense layer of highly organized connective tissue with a lot of fat cells found under the skin of all cetaceans (whales, dolphins, and porpoises), pinnipeds (walruses, earless seals, and eared seals), and sirenians (manatees and dugongs). Of the four groups of marine mammals, only the sea otters lack blubber. Polar bears, which some include with the marine mammals, also have blubber. Blubber provides insulation for these warm-blooded animals, as well as functions as an energy reserve and streamlines the body, while the elastic fibers contained in blubber helps in swimming.

This adaptation of blubber, which is so important for marine mammals, also has been of historical importance for humans....

Overview and description

Blubber is composed of connective tissue fibers and vascularized fat found between the muscles and skins of particular marine mammals. The connective tissue is made of collagen, as is found in human connective tissue. Lipid-rich, collagen fiber-laced blubber comprises the hypodermis (Struntz et al. 2004), the lowermost layer of the integumentry system in vertebrates, lying immediately below the dermis of the vertebrate skin. The hypodermis consists primarily of loose connective tissue and lobules of fat, and typically has larger blood vessels and nerves than in the dermis. Blubber covers the whole body, except for parts of the appendages, and is strongly attached to the musculature and skeleton by highly organized, fan-shaped networks of tendons and ligaments.

Blubber can comprise up to fifty percent of the body mass of some marine mammals (Smith 2009) during some points in their lives and can range from a couple of inches thick in dolphins and smaller whales, to up to 4.3 inches (11 centimeters) thick in polar bears (Stirling 1988), to more than a foot thick in some bigger whales, such as right and [bowhead whales]]. However, this thicker layer of blubber is not indicative of larger whales' ability to retain heat better, as the thickness of a whale's blubber does not significantly affect heat loss. More indicative of a whale's ability to retain heat is the water and lipid concentration in blubber, as water reduces heat retaining capacities, and lipid increases them (Kvadsheim et al. 1996).

Function

Blubber serves several different functions. It is the primary location of fat on some mammals, and is essential for storing energy. It is particularly important for species which feed and breed in different parts of the ocean. During these periods the species are operating on a fat-based metabolism. Recent research also shows that blubber may save further energy for marine mammals such as dolphins in that it adds bounce to a dolphin's swim.

Blubber is, however, different from other forms of adipose tissue in its extra thickness, which allows it to serve as an efficient thermal insulator, making blubber essential for thermoregulation. Blubber is also more vascularized, or rich in blood vessels, than other adipose tissue.

Blubber has advantages over fur (as in Sea Otters) in the respect that although fur can retain heat by holding pockets of air, the air pockets will be expelled under pressure (while diving). Blubber, however, does not compress under pressure. It is effective enough that some whales can dwell in temperatures as low as -40 degrees Fahrenheit. While diving in cold water, blood vessels covering the blubber constrict and decrease blood flow, thus increasing blubber's efficiency as an insulator.

Blubber can also aid in buoyancy, and acts to streamline the body because the highly organized, complex collagenous network supports the non-circular cross sections characteristic of cetaceans.

Research into the thermal conductivity of the common bottlenose dolphin's blubber reveals that its thickness varies greatly amongst individuals. However, blubber from emaciated dolphins is much worse of an insulator than that of non-pregnant adults, which in turn have a higher heat conductivity than blubber from pregnant females and pre-adults.

Maternal care is extremely important to the survival of offspring that need to develop a thick insulating layer of blubber. The milk from the mammary glands of marine mammals often exceeds 40 to 50 percent fat content to support the development of blubber in the young.

Human Influences

Uses

Muktuk, (the Inuit/Eskimo word for blubber) formed an important part of the traditional diets of the Inuit and other northernly peoples because of its high energy value. Seal blubber has large amounts of Vitamin E, selenium, and other anti-oxidants that hinder oxidation, which slows the formation of the free radicals that start a wide variety of diseases. The positive effects of consuming blubber can be seen in Greenland; in Uummannaq for example, a hunting district with 3000 residents, no deaths due to cardiovascular diseases occurred in the 1970s. However, emigrants to Denmark have contracted the same diseases as the rest of the population. The average 70-year-old Inuit with a traditional diet of whale and seal has arteries as elastic as that of a 20-year-old Danish resident.

One of the major reasons for the whaling trade was the collection of whale blubber. This was rendered down into oil in try pots or later, in vats on factory ships. The oil could be then used in the manufacture of soap, leather, and cosmetics. Whale oil was also used in candles as wax, and in oil lamps as fuel.

Blue whales can yield blubber harvests up to 50 tons.

Toxicity

Recent studies suggest that blubber contains naturally occurring PCB, which are cancer causing and damage the human nervous, immune and reproductive systems. . It is not known where the source of this PCB is. Since toothed whales typically place high on the food chain, they are bound to consume large amounts of industrial pollutants. Even baleen whales, by merit of the huge amount of food they consume, are bound to have toxic chemicals stored in their bodies. Recent studies have found high levels of mercury in the blubber of seals of the Canadian Arctic.

References

ISBN links support NWE through referral fees

1. Education Resources for Teachers—Blubber Experiment.

http://www.tmmc.org/learning/education/teacher_resources/blubber.asp MMC n.d.

1. Arctic Facts-Blubber.

http://www.athropolis.com/arctic-facts/fact-blubber-whale.htm Facts: Cold, Icy, and Arctic.

thick layer of vascularized fat found under the skin of all cetaceans, pinnipeds and sirenians. S.E. Smith copyright © 2003 - 2009

Bob Hirshon Ann Pabst http://www.sciencenetlinks.com/sci_update.cfm?DocID=10 Bouncy Blubber Science NetLinks 11/15/2000

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Journal of Thermal Biology Volume 21, Issue 2, April 1996, Pages 123-128

SeaWorld/Busch Gardens Animal Information Database http://www.buschgardens.org/infobooks/Bottlenose/adapaqdol.html Adaptations for an Aquatic Environment 2002

http://www.seaworld.org/infobooks/polarbears/pbadaptations.html Polar bears 2002

Stirling, Ian. Polar Bears. Ann Arbor: The University of Michigan Press, 1988.

<ref>Struntz DJ et al. "Blubber development in bottlenose dolphins (Tursiops truncatus)." PubMed. From http://www.ncbi.nlm.nih.gov/pubmed/14666521?ordinalpos=3&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

J Morphol. 2004 Jan;259(1):7-20.Click here to read Links
   Blubber development in bottlenose dolphins (Tursiops truncatus).
   Struntz DJ, McLellan WA, Dillaman RM, Blum JE, Kucklick JR, Pabst DA.

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