Subject: pineal glands and placentas

Caroline Margaret Delong (
Tue, 20 Apr 1999 21:59:37 -1000

On Mon, 19 Apr 1999, mellissa marshall wrote:

> Caroline,
> I am a 3rd year student of Veterinary Science and whilst we learn lots 
> about economically important animals like dogs and cows, we only 
> briefly touch on marine mammals. I've got lots of questions I'd love 
> to ask you but I'll limit it to two:
> 1. The Pineal Gland : I know that the pineal gland is rudimentary in 
> cetaceans, but I was wondering if this could be due to the fact that, 
> as olfactory capabilities have  regressed in whales, the rest of the 
> epithalamus has decreased in size and importance as well? What 
> interests me is that the pineal gland is considered so important in 
> seals where it is very large, and may have something to do with deep 
> diving adaptations (through anti-oxidative effects of melatonin???)but 
> if this is true why have whales developed in the opposite direction? 
> (I know it is generally thought of as having a thermoregulatory role 
> but I like this idea better...).

Dear Mellissa,

Marine mammal neuroanatomy/ general anatomy and physiology are outside
my areas of expertise.  I can provide you with some references on work
other scientists have done looking at cetacean brains and perhaps one of
those can lead you to an answer.  I suggest that you consult a marine
mammal vet, such as Dr. Sam Ridgway, for answers to questions as specific
as yours. I also suggest looking at the website for the International
Association for Aquatic Animal Medicine: 
This site may lead you to people or papers that can help you with your

Here are some references I have on cetacean brains:
Jacobs, M.S., McFarland, W.L., & Morgane, P.J.  (1979).  The anatomy of
the brain of the bottlenose dolphin (Tursiops truncatus).  Rhinic lobe
(Rhinencephalon): The Archicortex.  Brain Research Bulletin, 4(1), 1-108.
(lots of references in back)
(1971). Rhinic Lobe (Rhinencephalon). I. The paleocortex.  J.Comp.
Neurology 141: 205-272.

McFarland, W.L., Jacobs, M.S., & Morgane, P.J.  (1979).  Blood supply to
the brain of the dolphin, Tursiops truncatus, with comparative
observations on special aspects of the cerebrovascular supply of other
vertebrates.  Neurosci. Biobehav. Rev., 3, supp.1, 1-93.  

Morgane, P.J., & Jacobs, M.S.  (1972). Comparative anatomy of the cetacean
nervous system.  In: Functional Anatomy of Marine Mammals Vol. 1., R.J.
Harrison (Ed.), p. 117-244.  London: Academic Press. 

Glezer, I.I., Jacobs, M.S., & Morgane, P.J.  (1988).  Implications of the
"initial brain" concept for brain evolution in Cetacea. Behavioral and
Brain Sciences, 11, 75-116. 

Helmut Oelschlager- you mentioned olfactory capabilities
Oelschlager, H.A.  (1992).  Development of the olfactory and terminalis
systems in whales and dolphins.  In: Chemical signals in vertebrates VI,
R.L. Doty & D. Muller-Schwarze.  New York: Plenum Press 

> 2. With regards to placental development, are there any adaptions to 
> protect the foetus against changes in pressure?
> If you could answer these questions for me I would be eternally 
> grateful.
> Thanks,
> Mellissa Marshall

Again, outside my area.  I do have a paper on the female dolphin's ability
to thermoregulate the area surrounding the uterus (describing the
subdermal sheath around the torso and the blood vasculature structure),
but no papers on the dolphin's ability to protect the fetus against
changes in pressure.  Try looking in the March 1997 issue of Discover for
Pabst and McLellan's article and glance through the references for
good prospects. 

I hope this helps!

Best Wishes,