Morgan tears 4 and 5

Elaine Morgan (Elaine@desco.demon.co.uk)
Wed, 01 Nov 1995 22:15:47 GMT

Question 4. Do aquatic animals weep?

It may or may not have any relevance to AAH but some aquatic
animals certainl shed tears which are not "reflex" in the
sense of reacting to irritation of the eyeball.
These tears are saline secretions produced by salt glands.
Salt glands are found in marine birds (but not land ones) and
also in marine ( but not terrestrial or freshwater)
crocodiles, chelonians, iguanas, and snakes. (Salt Glands in
Mrine Reptiles, l958. by Knut Schmidt-Nielson, and Ragnar
Fange, Nature, Vol 182, 783-785.September 2oth.)

The glands can be activated by injecting seawater into the
stomach. In retiles the secretion sometimes exits through the
nasal cavity (marine iguana) but more frequently via the eyes.

Question 5. Do aquatic *mammals* weep?

Mammals do not evolve salt glands, passibly because their
kidneys are more efficient than those of reptiles.
Schmidt-Nielson reported (op. cit) "When we injected them
(seals) with salt solutions that stimulate the salt glands
of birds and reptiles, they merely increased their output of
urine"

Seals and walruses have been marine for millions of years and
have had plenty of time to evolve such efficient kidneys.
Apes' kidneys however are not nearly so efficient Humans
cannot drink seawater with impunity (sea water 3% salt, human
urine 2% salt) It is possible - an unprovable speculation
like so much inthis field - that if an aquatic ape populations
was *suddenly* subjected to the necessity of life in a salione
environment it might have been more expedient to step up
sodium excretion through other auxiliary channels (lacrimal
and eccrine) even though their out put like that of the
kidneys is normally hypotonic. Some outlet or other would
have had to be made more concentrated. The kidneys are vastly
more complex than tear and eccrine glands and would take
longer to modify.

For whatever reason, seals do shed non-relexive teARS. As far
as I know that fact is not disputed: rather it is explained
away, as follows.

Apart from psychic tears and reflex tears there are residual
teras - a small constant output of fluid just sufficient to
coat the eyeball with a film of moisture. A naso-lacrimal duct
in the inner corner of the eye normally channels this fluid
into the nasal cavity where it evapoorates and is breathed out
with vapour from the lungs. Seals have no nasolacrimal duct,
so it is argued that when seals "weep" it is merely because
th residual tears flow out instead of being re-routed.

I don'y buy that. If it was true the traces of tears would be
(a) barely detectable and (b) present in all seals at all
times. But films and photographs of breeding colonies make it
clear that most of the anmals show no trace of tears while a
small minority at any one time are weeping profusely. As far
as I know no one has tried to investigate why this is, excpet
Schmidt Nielsen's experiment with its negative result.

Now the sea-otter and a confession (JDM, prepare for rapture):
I cannot give a reference for this quote, which runs :"I have
sometimes deprived females of their young on purpose, sparing
th lives of the mothers, and they would weep over their
affliction just like human beings."

In recent weeks my standard of source-crediting and
page-numbering - I hope you have noted - has been impeccable.
This is all due to JDM and Natural Selection. As the predator
has sharpened his weapons, his intended prey has strengthened
her defences. I have admitted past errors, recited fifty Hail
Darwins, and vowed not to sin again.

This time I can't help it. That quote is in a book by
G.W.Steller, which I read in the library of the Zoological
Society of London when I was a raw beginner and had no system.
I copied out passages but not alas the title and publisher.
When I returned there years later it could not be found and
even the British Museum Library does not seem to catalgue it,
at least in the English edition in which I read it,

Steller was the discovere of the Rhytina (Steller's sea cow).
The book also had good descriptions of that animal and how it
moved, part swimming and part walking, like a cross between a
manatee and a hippo. He wrote a work in Latin (De Bestiis
Marinis) as well as papers in German. There must be a copy of
his book somewhere, in some language. If anyone can help me
trace it I will be eternally grateful. Failing that, if JDM
is determined to call me a liar and pursue this to a
shoot-out, I may have to go back to the B.M. and give the
quote from the Latin version. In Latin, of course, With the
page in Roman numerals, just to show off.

More follows. (I say this so that everybody who is bored
stiff with this stuff, and I know they are many, can get ready
to duck)

Elaine.