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.
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 fin...as 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!
This archive was generated by hypermail 2b30 : Tue Nov 25 2003 - 16:35:52 EST