Circulatory system of dolphins

From: Dagmar Fertl (
Date: Fri Nov 21 2003 - 11:24:56 EST

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    Dear Dagmar Fertl,

    My name is David, I'm 10 years old and I go to Irwin Park School in West
    Vancouver BC in Canada. I have been assigned a project to compare the humans
    respiratory and circulatory systems with the dolphins. I have had a hard
    time finding diagrams of dolphin's heart and other circulatory information.
    Could you suggest any books or internet resources that you think will help
    me, or could you email me any information. I am very keen on science and you
    need not simplify the info for my benefit.

        With thanks,

        David Stephen-Tammuz.
    Dear David,

    What a great question. Sorry it took me a little longer to get back with
    you, but I had to do some serious digging around for diagrams. By golly, the
    things are just not easy to track down, as you know. I assume since you
    didn't ask about the respiratory system, that you've already found
    information on that? The anatomical and physiological adaptations in the
    dolphins' respiratory system are just fascinating. That said, I will focus
    on your request for help with the circulatory system.

    Just as some background for anyone else looking for information related to
    this topic, I do need to provide a little information that might be a bit
    simplified for you. I looked at an article "Circulatory System" by Paul J.
    Ponganis in the "Encyclopedia of Marine Mammals" which was published in 2002
    by Academic Press and edited by W.F. Perrin et al. Although the circulatory
    systems of marine mammals follow the general mammalian plan, they are most
    notable for features associated with the diving response, thermoregulation,
    and large body mass. Specific features of the circulatory system vary with
    orders, families, and species (we're now talking about not just cetaceans
    but pinnipeds as well in this case and for just a little to follow). These
    adaptations include large blood volumes, large capacitance structures
    (spleens and venous sinsuses), venous sphincter muscles, vascular
    adaptations for thermoregulation, aortic windkesssels, and vascular retia.

    The basic structure and size of hearts in cetaceans are typical of mammals.
    The four-chambered heart with right ventricular outflow to the lungs and
    left ventricular output to the systemic circulation, weighs 0.5-1.0% of body
    mass in most small cetaceans (dolphins). Both the foramen ovale and the
    ductus arteriosus are closed in adult cetaceans as in other mammals.

    There is a diagram of a porpoise heart in a book entitled "Whales" by E.J.
    Slijper, an old book (first published in 1962, reprinted in 1979). I could
    see about making a scan of the page and sending it to you by email, but
    you'll need to write me back again, and I'll send it directly to you, and
    not to WhaleNet. Alternatively, if you can wait for me to mail you a copy,
    send me your address.

    You asked about Internet resources. The following link is to a scientific
    paper about some studies done on a dolphin heart. Quite honestly, the
    article was even above my head in many places, but there are some cool
    photos that might be neat for a school report (?).

    As for the circulatory system itself, we're a bit stuck here. I have a
    diagram from the same book of the main veins in a porpoise. Alternatively, I
    do have a color diagram of the circulatory system of a seal that appears in
    Sam Ridgway's "Mammals of the Sea" published in 1972. That book is not easy
    to track down, unless you are near a university library. There are some
    universities up your way doing marine mammal research, so it's possible that
    your public library could interlibrary loan a copy of the book for you.
    Otherwise, let me know which picture(s) you're interested in, and I'll get
    them to you. (Just remember that I take the weekends off).

    In my opinion, the absolute coolest thing about the circulatory system of
    dolphins and whales is the rete mirable (or retia mirabilia), the parallel
    pattern of counterflowing arteries and veins, present in the flukes and
    flippers of cetaceans. Countercurrent anatomy is even in the reproductive
    organs of these animals! This system helps with thermoregulation. The
    following website gives some very basic information on this and has a
    diagram as well. You should be able to find plenty of information on the
    rete mirable online.

    What's cool to show is a cross section of the dorsal if you just
    sliced it off at the base, b/c you can see the countercurrent system...well,
    in detail with a microscope. There are diagrams in the Slijper book as well
    as in a book chapter by Pabst, Rommell and McLellan entitled "Functional
    Morphology of Marine Mammals" in "Biology of Marine Mammals" edited by J.E.
    Reynolds and S.A. Rommel, published by Smithsonian Press in 1999. If you
    need that diagram, just let me know.

    Ok, whew, hope this helps!
    Dagmar Fertl

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