Ok, Nautilus lovers, here's a lot of information about argonautids...
you sent me off to follow my curiosity and I sure learned a lot!

I have always kind of thought, when I thought about it, that is, that
the female argonaut built her boat, shared it with her miniscule mate,
laid the eggs in it and brooded them, then sent it off like baby Moses
in the bullrushes, to float wherever the currents took it, as the eggs
hatched.  And that that was why we found small, medium and large shells
on the beaches...small from young females, large from older ones. Or
better fed individuals. I really didn't know. But this thread got me
wondering. How did the timing of this work?  What did she do when she
cast adrift her pretty boat full of babies?  Start a new shell
immediately? Or go on vacation and swim the Atlantic solo or something?
And what happened to her 5mm live-in lover if she bailed out of the
boat? Could he even swim with that stumpy atrophied little body?

I was wrong, it seems! We all are wrong.

At the risk of oversimplification, I turned to the "Little Green
Abbott,"  Seashells of North America to see if I could find anything
about the life cycle of the paper nautilus, Argonatua. It seems to me
that every picture I ever see of the things, there is the female,
sailing along in her elegant little boat, and I knew there was one or
more pictures in that beginner guide for most of us. Sure enough, both
Argonauta hians and A. argo are pictured there floating in their shells.
A. hians has its specialized shell-building arms wrapped about the
shell, one arm to each shell side in the position in which the arms form
that shell. The A. argo is waving her specialized arms in the air (or
water...Zim's picture isn't too specific on that!)

So I went further:  Kilburn and Rippey's 1982 Seashells of Southern
Africa (a great book to have! Much about living mollusks.) says:

"Argonauts or Paper Nautiluses are among the strangest  of
cephalopods...the female appears to spend all her life sheltering within
her shell, and probably never vacates it under normal circumstances.
Argonauts are generally found floating near the surface of the sea, but
can swim actively and may cling to floating objects. The dorsal part of
the body is cryptically colored with blue or purple, the underside being
countershaded white. Argonauts are normally slow swimmers and drift
through the water with their arms folded backwards, the first pair
enclosing the shell on either side like a silver sheath; when alarmed
these can be withdrawn suddenly, producing a brilliant flash that may
frighten away predators."

Elsewhere we are told that breaks to the shell can be repaired. So it
would seem that the female keeps her shell for life, enlarging and
repairing it as needed. Hmmmm!

Then I turned to my new favorite, Beesley Ross and Wells' 1998 MOLLUSCA
The Southern Synthesis.  The section on cephalopods is by Katharina
Mangold, Malcolm R. Clarke and Clyde F.E. Roper. Here I learned that
"the web or membrane on the dorsal arm of the female, besides secreting
the shell, acts as a receptor in feeding. When disturbed, red
chromatophores of the upper part of the web, arms, eyes, head, funnel
and mantle, expand, providing a startling colour over a blue and white
background (Young, J.Z. 1960) A second colour pattern is produced as a
sudden flash of white as the web is withdrawn."

 Thus the explanation of the white flash mentioned in Kilburn and
Rippey.

They seem to prey upon pelagic animals, in confirmation of their life
floating in a shell. Heteropods, pteropods and sometimes other octopods
are found in the stomachs of A. hians. In turn, tuna, some other large
fish, seals and sharks are known to eat them.

About the eggs, they are laid in clusters connected by a stalk and
attached to the apex of the sehll, occupying its posterior part.
Clusters of up to three different developmental stages are found in the
shell!! So some hatch then others and then others. Maybe it is a
continual process?

Also, the female argonautids do not go off and die, all worn out from
the rigors of brooding the eggs and no food when their babies hatch,
like octopi do. "Female argonautids begin to reproduce when young, and
continue to grow and reproduce for a long time. Recently mature females
contain only a small cluster of eggs, all at the same stage of
development. Eggs of A. hians and A. boettgeri were .85mm to 1.1mm in
the first and third stages of development. And a female with a mantle
length of 35 mm carried about 40,000 eggs in her floating nursery! (All
from Nesis, 1977)

One more fact:  The mention of clinging to floating objects in Kilburn
and Rippey was borne out by The Southern Synthesis:

"A chain of argonautids clinging to each other may occur, perhaps
involving 20-30 animals of similar size, in which the first female
usually holds onto some other object while other females in the chain
hold onto the preceding one on the ventral part of the shell (Voss G.L.
and Williamson 1971; Nesis 1977)."

This might be an explanation for Kate's sea bird eating not one but
several individuals.

I can scan some pictures if anyone wants to see them...I've run across a
number of them... but have no place to post them.

Well, I have dallied pretty seriously here...better get back to work or
there'll be a January American Conchologist instead of a December one.

Lynn Scheu
Louisville KY
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