| The Gray Whale Advocate
Newsletter June, 2002 edition. Internal mechanisms contributing to the thermal regulation process in the Gray whale species and possibly in other baleen whales. Contents, both editorial and photographic are copyright 2002, Keith E. Jones. Viewpoints and original research concerning the Gray whales internal thermal regulation mechanisms are exclusively by Keith Jones, except as noted. Discussions with dozens of veterinarians, medical doctors of various disciplines and research scientists were all important in helping me come to the conclusions that I discuss below. This month I want to talk about the anatomy of a gray whale. I will explain how the bones in the head of a whale may be part of a complex mechanism that has evolved to protect gray whales (and other baleen whales) from the adverse affects of living in the cold Arctic water. Before I get into this month’s topic I must plug our one and only sponsor, Baja Jones Adventure Travel. The season brochures are ready and have been mailed. If you didn’t receive one, email us and we’ll get it to you. We now have video clips on line. They are brief, but tell the story. Follow this link to the new Video page:http://www.greywhale.com/video.htm Trip prices this season begin at $1,595 for a SIX day drive down trip. Air charter trips start at $1,750. We have two options this year. We can now accommodate as few as two people on the air trips. Or we can take as many as six at one time. I’ve spent a lot of time looking at whale skeletons the last few years. The subject of this article is my speculation on how some unique characteristics of the internal anatomy in the gray whale helps them to survive in cold water.
An interesting talk at the Cabrillo Aquarium by Dr. John Heyning three years ago left me thinking about the head and mouth structure. Dr. Heyning and a colleague, Dr. James Mead dissected the tongue of two gray whales and observed a unique blood vessel structure that they termed the lingual rete. To read the article by Dr. Heyning go to: http://www.nhm.org/research/mammals/jj/The pair of researchers clearly illustrate in their published article how the blood vessel system works as a heat exchanger to protect the whales tongue from the cold environment. When eating, the tongue and inner mouth of the whales are exposed to constant frigid water temperatures. Yet the tongue and mouth temperature remain very close to the internal body temperature of about 99 degrees. After looking at gray whale bones for a long time, I noticed a series of holes in the lower jaw bones. There are others scattered throughout the bone structure of the head, but for this article I deal only with the lower mandible. A foramen is a naturally occurring hole in a bone. There are neural foramen which allow nerve bundles to enter into the interior of a bone. There are nutrient foramen which allow arteries and veins to enter and exit the bone structure carrying needed nutrition to the bone marrow. There are foramen through which both nerves and blood vessels enter. In most land mammals, such as dairy cows, there is only one nutrient foramen in each bone. A single hole allows blood vessels to enter and exit the bone structure. Inside the bone a single large artery branches to many smaller vessels, which carry the nutrients throughout the interior of that individual bone.
In contrast to this human bone structure here is a photo of the lower right side jaw bone of a gray whale. This sketch is preliminary and still only partially substantiated. Additional work including dissection needs to be accomplished before this working theory can be validated.
Notice that there are eight nutrient foramina in this photo. Interestingly the left side jaw bone of this individual had seven foramina. That caused me to count the quantity of holes on every whale skeleton I could find. Of a dozen skeletons, all but one had one more foramen in the right side than on the left side lower jaw bone. Placing that fact in conjunction with the observation that most gray whales are thought to be right side feeders, makes for some interesting speculation. Does the right side need added blood flow because of repeated contact with cold mud? Or does the constant impact and abrasion of the right side cause more blood to flow? I hope someone chooses this topic for advanced study. Not visible in the photo above are the numerous and as yet uncounted foramina through which the veins exit the bone. Those holes are located on the opposite side of the bone and at the lowest point on the inside of the mouth. If you look closely you can see where the blue dotted veins are drawn in. For clarity I’ve only drawn some of the veins. They actually exit the jaw bone all along the lower inside from one end of the bone to the other.
Another observation about the make up of the mouth and head of gray whales is that this area of the animal contains the thinnest layer of blubber. Inside the mouth there is no blubber. Around the entire head structure there is only a very thin layer of fat. Those of us who have had the opportunity to pat a whale on the head know that the bone is not buried beneath a foot of blubber. It is close to the skin surface. I think that the dense and relatively heavy bone structure in the head of the whale acts as a large heatsink and radiator. The warm arterial blood flows into the bone through the numerous thermal foramen and then radiates warmth to the surrounding tissue. The bone acts much as radiator does inside a New York apartment building. This is why there are so many holes for blood vessels to enter and exit the jawbone. If there were only one foramen as in the photo of the human humorous bone above, by the time the blood supply moved to the far ends of the bone, it would be much colder. It would not supply the warmth that is needed to evenly regulate the temperature of the surrounding tissue. There would be hot spots and cold spots in different areas on the face of the whale Because the multiple holes in the jaw bone are likely required for thermal regulation, rather than nutrition I refer to these foramen as "thermal foramen". This is to differentiate them from those foramina that are only for blood nutrient supply. I welcome comments. PS: I have guardedly promised many people that the proof drafts of my book, "The Baja Jones Field Guide to The Gray Whale" would be ready for this coming Baja whale watching season. I’m already falling behind this self imposed schedule, but I maintain my optimism that the proof copies will be available for those of you traveling to Laguna Ojo de Liebre with me this coming year. I promise you that it is more interesting reading than what you just waded through in this months’ newsletter. That’s all for now. Keith (baja) Jones Baja Jones Adventure Travel and coming soon: Individuals who receive this newsletter have either asked to be on our email list or they have sent an email to one of the following websites or individuals: Keith E. Jones, www.greywhale.com , Baja Jones Adventure Travel or www.bajajones.com . If you do not wish to continue receiving this newsletter simply reply requesting removal. |
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