OK, it seems a pity that these obscure little octopods are so rarely mentioned on these pages.

What's going on with these animals? Here we are with this advanced octopus that insists on creating a very ancient ammonite-like shell in which to breed its young. How is this? Is this coincidence or not?

How well studied are these animals? Has anyone ever kept them in captivity?

Never heard of them, but now youve sparked my interest! So the shells look like this (http://members.tripod.com/mgrist/images/640/shells/Argonaut.jpg)?

I've read about them a while go, I think they've been kept before but the longest was 2 weeks, SOS said he kept one for a few days....

http://www.dal.ca/~ceph/TCP/Argo.html

They are amazing!!

That pic on Ceph Page makes them look as if their body is covered in suckers!

There is some good information and pictures of argonauts in the book Cephalopods: A World Guide

Aint those the guys what sailed with Jason, after the golden fleece?

Dr. Woods posted this site on the Ceph list.
Argonauts (http://www.rogerandjudycarlson.com/gallery/recent)

If the argonaut has the ability to secrete a shell with its arms, why would it need to copy an ammonoid shell. If the argonaut was using empty ammonoid shells for a nest in the mesozoic how did it remember what an empty ammonoid shell looked like by the time they developed the ability to secrete one that looked like an ammonoid shell? Seems to me it would be easier to just use some other shell for a nest, than to spend years trying to figure out how to secrete one. :bonk: This would foul-up my theory that the octopods learned to coil their arms to look like a school of ammonoids (pedators would grab an arm, thinking it was an occupied shell).

There is probably a little "coiled shell" in all of us. :D

They are fabulous animals.

Another problem with linking ammonoids to argonauts is the length of time elapsed between the extinction of the ammonites, i.e 65 mya, and the earliest recorded argonaut, i.e 25mya. How could an octopod retain some form of ancestral memory for 40 million years before deciding it suddenly wanted to secrete ammonoid-type shells? (Argonaut date here taken from the Tree of Life pages). Even given that the fossil record is incomplete, this seems an unlikely amout of time to have passed with no fossil argonaut shell remains if they were out there in the immediate post-Cretaceous. :grad:

In addition, the chambered ammonite shell was composed of aragonite, the unchambered argonaut calcite. The more one thinks about the theory the more ridiculous it sounds! It's all coincidence in appearance, I'm sure.

:ammonite: :arrow: :bluering: = x

The more you see and learn, the more things just don't seem to make much sense...I am sure there is an underlying rythym to all of it, but I , for one, seem to be left out of the dance!
Fascinating subject Phil...it never occured to me at all...most perplexing.
greg :oops:

I haven't heard much about them or seen one. All I know is people call it a paper nautilus.

Hi,

I collect cephalopod shells and specialise in animals of the genus Argonauta and Nautilus (though I couldn't even spell the screen-name I wanted right :oops: :bonk: ). Does anyone how many species there are?
I'm sure that more than one species is being treated under the name Argonauta hians due to the diversity in shell shape, size and colour.

Michael.

Hi Michael.

It found is extremely difficult to describe the animals of any of these Argonauta species because they were almost always removed from the shells (with collectors having separated them). The literature is also full of inconsistent and partial descriptions of anatomical characters/character states, and usually for the female only (the male of any species is actually quite poorly described).

It would make for a superb Masters thesis!!! Secure animals with shells and then describe the morphology and anatomy of each. As the hectocotylus of the male is detached and ?swims to the female's mantle, becoming lodged around the base of her gills, detailed examination of these detached structures (often up to 6 per female, mutiple paternity) might enable someone to identify the male morphology of each species (especially if a male with attached hectocotylus is found).

As for A. hians and how many species are being confused with it, it would be very nice to see some of the variation you are encountering in this species. Any chance of a series of photos online?
Kindest
Steve

Hi Steve,

Thank you for that informative reply. I'll try to get a few photos of the shells online.

Michael.

I've hosted all the photos described below here: http://www.picturetrail.com/gallery/view?p=999&gid=4081363&uid=2101892&members=1 (Note: The pictures are of a high resolution so they may take some time to load.)

The first photo is of Argonauta hians "No. 1" which seems to be a very common type. Shells of this Argonaut are usually cream or light sepia in colour and are quite compact. The shell's surface is very smooth with ribs which are barely visible. The tubercles (knobs on top of the shell) are very small and rounded. I have found that shells of this type of A. hians usually don't get very large. Most specimens which I have seen are below 6 cm in size and I have never seen any over 9 cm. Most representatives of this form seem to come from the Philippines.

The second and third photos is of Argonauta hians "No. 2" which seems to be uncommon. This type seems to grow much larger; i have seen numerous specimens past 10 cm (I myself have a shell of 122 mm, a WRS). The shells of this variant of hians usually have a much darker colour (dark brown to even black) and display much more prominent tubercles and ribbing. They also display large "spikes" protruding from both sides of the shell (visible in the second photo of the representative of this variant). A. hians "No.2" seems to be most abundant in the waters surrounding Taiwan and Japan.

Photos 4 through to 6 display different specimens of Argonauta boettgeri, a species often confused with A. hians. These shells seem to be the smallest of all the paper nautiluses (the WRS is listed at a mere 61.9 mm). A. boettgeri originates from Southern Africa (especially Mozambique, where most specimens are from). These are rare finds and vary wildly in degree of pigmentation (as can be seen in the three pics), but most seem to be of a dark colour (dark brown/black). The specimen from S. Africa in photo No. 6 seems to be an "albino", displaying almost a complete lack of pigmentation (sorry for the bad photo - it's the best one I could take o_0). Another characteristic of this species is that the shells are usually finely granulated and display promiment tubercles and well developed ribs (which are usually "wavy"), which alternate in length (one long, one short, etc.).

Photo number 7 is of the very rare Argonauta nouryi. The shell pictured is 87.3 mm in length (my other specimen is 93.9 mm - WRS?), which is at the higher end of their size range. This is one of the rarest Argonauta species and can only be found in the waters around Mexico and Baja California. If my memory serves me well then there have only been two known strandings of this species (both my shells came from the 1992 stranding). The shells of this species cannot be confused with any other being probably the most elongate of any paper nautilus. The shells are of a white or cream colour (with the oldest tubercles having a brownish pigmentation) and possess numerous small knobs on the keel. The surface of the shell is very smuth and has a large number of underdeveloped ribs.

The final photo is of a curious specimen of a shell which seems to share traits of several different species. For the most part it looks like A. boettgeri: it is of a dark colouration and displays very prominent tubercles and ribbing (having the characteristic "wavy" shape). It is also finely covered in small "granules", another characteristic feature of A. boettgeri shells, but it is well outside its normal size range at 75 mm (which would make it the World Record Size by almost 1.5 cm) and displays those prominent spikes which in the description for A. hians "No. 2". Also, this specimen came from Taiwan waters, on the other side of the world when compared to the known distribution of A. boettgeri. Could it be A. cornuta?? I am not sure as the few photos which I have seen that supposedly show this species are very conflicting and also do not seem to show a distinct species. Due to the lack of knowledge on this subject I cannot positively identify it for the moment.

Please let me know if you would like to see any more Argonauta (or Nautilus) shells as my collection consists of over 80 specimens, so this is only a small fraction of it.
Also, I would be interested to know if anyone knows how large Nautilus shells actually get or has any information on the validity of the species Nautilus repertus. In the 2001 edition (newest) of "The Registry of World Record Size Shells" the largest Nautilus pompilius specimen is listed at 253 mm. A shell which I received labelled Nautilus repertus is considerably larger than this at 268 mm, so I am curious as to how large these creatures actually get.

Look forward to reading your replies,
Michael.

8) Awesome pics.


Might I suggest a quarter for reference? :)

Heh, thanks. I tried to make the photos as clear as possible so that a lot of detail would be visible. Hope I achieved that. :)

I've added 11 new photos to my Argonauta photo album, if you'd like to have a look: http://www.picturetrail.com/gallery/view?p=999&gid=4081363&uid=2101892&members=1

Pics 9-11: Argonauta nodosa. Typical Australian form (in my opinion the most magnificent type), Brazilian form (more elongate shell with less developed tubercles and ribbing) and an intersting specimen of an Australian A. nodosa with slightly exagerrated features (and even two small "spikes" like those on A. argo or A. hians "No. 2").

Pics 12-14: Argonauta argo. Typical Australian form, quite a large specimen (about 18 cm). Then there is the South african form which is usually much smaller and more elongate, which underdeveloped "spikes" (some specimens lack them completely). The third is a specimen from Taiwan waters. A. argo shells from this region seem to vary widely in shape and form.

Pic 15: An example of quite considerable shell restoration in a medium-sized specimen of A. argo.

Pic 16: Freak specimen of A. hians from Taiwan.

Pics 17 & 18: Two old pics showing both sides of my A. hians (122 mm) from Taiwan.

Pic 19: An old pic of my Argonauta nouryi (93.9 mm) from Baja California. (Photo courtesy of Guido T. Poppe who I bought it from).

Well, that's most of the major species covered now. :)

Michael.

Very nice Gallery...great pictures, and great information!
thanks!
Greg

Wow,

Thanks for the fascinating detail and images. The argonauts are a more varied group than I had realised, it's fascinating to see the variation in form in the shells on your website.

As for Nautilus repartus, from searching around on the net it seems that there seems to be no consensus about it. However most sources seem to indicate that it is a synonym of N.pompilius, just a rare and large Indonesian subspecies. I'd love to see images of your collection of Nautilus shells, especially. Allonautilus!:nautilus:

Cheers,

Phil

I've only got one Allonautilus at the moment: a quite large specimen of Allonautilus scrobiculatus (184 mm) from Milne Bay, New Guinea. As you can probably see from the photo it still needs some cleaning to remove the remenants of the periostracum.

The second Nautilus photo is of one of my favourite specimens; a very large Nautilus pompilius - 235 mm in size. This shell is very thick-walled and heavy. From Western Australia.

Michael.

Well, I'm absolutely tickled pink! Back in 1999 when I put the last piece of work out on New Zealand Argonauta species (recognising A. nodosa on the basis of animals and shells, and A. argo on the basis of shells only, excluding A. boettgeri from the New Zealand region (the species was included in error based upon a misidentification by Massy 1916)), I had only 2 small animals of A. argo available for comparison, loaned from the British Museum. It was very difficult to dissect this material (given it was on loan), and specimens that could be definitively identified as A. argo (given the shell was present) were extremely rare in collections (to the best of my knowledge). Consequently I was unable to contribute anything to our knowledge of the anatomy of this species.

Debbie Freeman, of the New Zealand Department of Conservation, also the whiz that gave us those sensational photographs of the sperm whale with the gouges over the head (after a rather serious battle with the colossal squid), has just contacted me and sent the following photos of an Argonauta argo just collected off central-eastern New Zealand, for which the shell, animal and eggs are all available. We've now finally got a specimen of this species from New Zealand waters, based upon a record of the animal, and accordingly can now examine it in greater detail than has hitherto proven possible, and describe both external morphology and internal anatomy. You'll not find a half-decent account of the anatomy of A. argo anywhere (or at least I was unable when researching the group).

I'll get this online as soon as I can, when I get the animal.

Debbie, thanks a million, as always (and she's given us permission to post these pictures).
Steve

http://www.tonmo.com/phpBB/download.php?id=2372

http://www.tonmo.com/phpBB/download.php?id=2370

http://www.tonmo.com/phpBB/download.php?id=2371

... and here's a couple of self explanatory pics, a juvenile female (minus shell), and a close up look at her eye (of no particular use to anyone, but one of my favorite shots).

http://www.tonmo.com/phpBB/download.php?id=4080

http://www.tonmo.com/phpBB/download.php?id=2373

Nice photos! :)

I was wondering if anyone else on these boards collects cephalopod shells?

Michael.

I collect really old ones :) :ammonite: :belemnit: :nautilus:

Steve,

You've reached the press again!!!

http://xtramsn.co.nz/news/0,,3762-3263567,00.html

:shock:

I was down at the local jetty yesterday, doing the old food collection for the squid, yet again, and one of the chaps came running down down, someone I regularly exchange a few words with, near-slid on the algal covered ramp, and told me that "I was tickled pink" There'd be something on the radio that this rare octopus had been found and sent to me. I did scratch my head on this one, wondering who on Earth had said anything, and had a laugh. All I can think of is that some reporter, having a rather dull day at work, decided to check out what had been going on in the big wide world, found tonmo, found this and then quoted it on radio.

New Zealand is such a nice country you know :mrgreen:

Either that or the Department of Conservation made mention of it somewhere in a press release.

The argonaut actually reached yesterday and is sitting in my freezer until next week. Another shell was also found yesterday.

"Crikey!" exclaimed Dr. Steve O'Shea, "Ain't she a beaut?"
He then bombarded the reporter with various stories about how Neil Diamond was in fact the leader of the lost tribes of Israel, winner of the cosmic hula contest, and an all around nice guy.
"He's an all around nice guy!" said the Doctor, upon a follow up interview regarding sea badgers and nautiloid predation.
Film at eleven.

I just got a copy of Monks & Palmer's Ammonites book, and find that they discuss two theories of why argonaut egg cases resemble ammonites, and I noticed this has been discussed here, too... unfortunately, they don't provide references for these, but they suggest:

1) early argonauts used empty, floating ammonite shells and evolved a way to patch up the shells using secretions from their arms, and "eventually got so good at it they could make a facsimile of an ammonite shell from scratch"

and

2) argonauts are "nude ammonites" that switched from using the shell for buoyancy to using it just for eggs (this is credited to Lewy 1996 but there's no bibliography to match this ref ) They cite two supporting bits: ammonites showed major sexual dimorphism, like argonauts, and other octopuses, particularly deep-sea octopuses but not other coleoids, have radula teeth that are "very like those found in fossil ammonites."

The Lewy paper is this one: http://geology.geoscienceworld.org/cgi/content/abstract/24/7/627

any comments? This is maybe more "fossils & history" but it fits in this thread, so I'll leave it here.

And for those in a sentimental mood, please find this wonderful collection (http://www.museum.vic.gov.au/caughtandcoloured/collectiondetail.aspx?strCat=Mollusc&IRN=1101289&mIRN=213084) of A. nodosa drawings.

As Phil points out in this thread (http://www.tonmo.com/forums/showthread.php?t=4078&highlight=fossil+argonauts), the first fossil Argonaut shells appear about 40mya, the ammonoids went extinct 65mya. It seems to me that the exhibitionist octopods would be more common closer to the 65mya time frame (both before and after) and most wouldnt have waited the 25ma to come out of the closet 40mya.:smile:

I'm actually just now righting a paper on the argonaut that I caught this past summer. Most of the papers I've read seem to go with the first theory that they used discarded shells found on the bottom and where able to at some point recreate it and also changed into a palagic life style. This was stated in a paper by Young (1960). The sexual dimorphism is probably evolved after it became palagic as it is more adventagous them. Just my thoughts.

Hmmm...I don't know...in fact I'm a Doubting Thomas, sorry. I just don't see where the evidence lies that ancient octopods used ammonite shells. Surely there are no fossils to verify this? Hermit crabs using ammonites for shelter certainly, but other cephalopods? Are there any late ammonite shells that show evidence of repair by a host?

I just can't see this idea of an animal developing an egg shell to emulate another creature's discards holding any water, especially after a 25 million year gap. Not only that, but the ammonite and argonaut shells are not only very different in form but in function too. A floating bouyancy chamber is not even remotely akin to an egg case; and is not a facsimile at all aside from a vague spiral shape. It is not chambered and has no siphuncle to name but two. The male argonaut does not secrete a shell, so if these animals hunted out and repaired ammonite shells for protection, why would this behaviour evolve to be sexually specific? Surely if the both the male and female would still be doing this - of course they don't as the function of the argonaut shell is utterly different and evolved for different reasons.

The similarities are purely cosmetic in my opinion and argonauts developed their egg cases wholely independently. They may look similar to our perception but the similarities are really just superficial. Of course I could be utterly wrong! :wink:

Hmmm...I don't know...in fact I'm a Doubting Thomas, sorry.

Hey Phil, I was thinking along the same lines, but not as brave as you to put it into words. Is making a spiral considered an easy form to replicate? I am trying to think of other animals that make a sprial. Foraminifera come immediately to mind.

Will have to think on this a little more...

For those with access to the Journal of Paleontology, this article (http://apt.allenpress.com/aptonline/?request=get-abstract&issn=0022-3360&volume=079&issue=03&page=0520) (from the aforementioned thread), has a nice review of Argonauts and the ammonoid-Argonaut connection.

Some octopus species carry there home with them. There is one that I've seen that will carry a coconut shell around with it. It is interesting that the female only has the shell so one would think its main purpose is for laying eggs as it provides little protection. Another interesting that the female can't survive without the shell it has no way of swimming, it will just lay on the bottom and die. The body posture is strange comparied to other ceph's with shells because all the arms are folded back into the shell. I think a good question is how the development of laying eggs on the shell instead of what most palagic octo's came about. Is it from when they lived on the bottom or came about afterwards.

yeah, my initial thought on reading it in Monks & Palmer was that both theories seem pretty implausible. Reading the actual paper made it seem a bit more reasonable, though, and it also seemed equally implausible that argonauts would develop an egg case that's so similar in shape to a shell found in other cephs yet not in many other critters.

Monks & Palmer introduce the topic with this observation:

The most curious thing about the argonaut is its egg case, particularly the fact that it closely resembles an ammonite shell , such as the Triassic ammonite Trachyceras. This is unlikely to be the result of convergent evolution, that is, a similar solution to a common problem, because the ammonite's shell and the argonaut's do completely different things. Could it be mere coincidence?

Come to think of it, since argonauts are free-swimmers that sometimes float on the surface, how to they get positive buoyancy? They have no phragmacone; most other cephs are either negative buoyant or ammoniacal, but I thought only squids and maybe vampyroteuthis had developed the ammonia buoyancy mechanism... are argonauts an example of that in octopods? Actually, Nixon & Young point out that "The female is neutrally buoyant, aided by a bubble of gas trapped in the upper part of the shell (Young 1960a, Voss and Williamson 1971, Roper 1972)" so arguments that the "egg case" is functionally distinct from proper phragmacones may be exaggerated... (although they don't mention that the animal can replenish the gas by some mechanism, or where the gas comes from in the first place... but they sink if you take it away).

Anyway, the Lewy paper addresses some of the questions a bit more. Part of his thesis is that ammonite macrononchs (presumed to be female) often have strange and restrictive-seeming body chambers at sexual maturity, so he hypothesizes that female ammonites, at the end of their lives, would seal themselves off to raise their young who would consume the mother in some sort of oedipal cannibalism feast when they hatch. That would explain another complaint about the theory, which is that the argonaut egg case is secreted from the arms, and is a different material than ammonite or nautiloid shells, which were presumably secreted from the mantle. It would also explain why heteromorph ammonites often have a final growth stage that seems to actively interfere with the body's orientation to do anything sensible.

Material-wise, ammonite shells are aragonite, and their aptychi are calcite. The Monks and Palmer book suggests that argonaut egg cases are calcite, but Hallucigenia found a ref that it's chitin:

argonauts use chitin! it's not CaCO3 at all!

and also notes that this info about argonauts:

wikipedia says males semelparous, females iteroparous

would seem inconsistent with Lewy's idea of argonauts sealing themselves off fatally as part of the brooding process..

Nixon & Young confirm that females brood for most of their lives, and say the shell is calcareous and structurally the greater part of it is finely prismatic, consisting of a thicker upper and a thinner under layer, between which is a thin layer of very fine, irregularly grained calcite (Boggild 1930, Noda et al. 1986).

Unfortunately, I had to leave when we were still discussing this, so I didn't really get her final thoughts on it...

One seeming flaw is that Lewy doesn't really explain why an argonaut egg case would look like the main ammonite shell, since if it evolved from some separate thing that was supposed to seal off the shell opening, why would it look anything like the shell?

I think it also raises another question, though: is there some aspect of cephalopod developmental biology control that favors mechanisms that produce spiral things? Such that when the argonaut needed to develop an egg case, it pulled some "spiral pattern" out of its genetic toolbox, even though it's applied through arms instead of mantle, and with a different material.

I agree with Monks and Palmer that it seems awfully weird that it would happen by chance, since we don't see too many spiral animal forms. It's not just spiral, either; in addition to the general spiral shape, its streamlining and ornamentation are rather typical of ammonites and not too common elsewhere. I can't think of a gastropod shell that is as similar, and I can't think of many other spirals in the animal kingdom at all, except maybe some brain structures, the cochlea, and rams' horns. (Although fans of the spirals and the golden ratio like to list nautilus as being kinda close to a "golden spiral," although measurably it doesn't seem locked to the phi, and fossil forms certainly aren't even though planispiral shelled cephs are closer to non-golden logarithmic spirals than anything else.)

One last comment: aren't argonauts extremely rare fossils, since their egg cases aren't much easier to preserve than soft-bodied animals? We seem to infer a lot of coleoid history from very few fossils...

edit: I removed the chitin note in wikipedia, since I found 3 sources that said it was wrong

Well they are molluscs and many do the spiral thing! Just look at your average gastropod, even if you look closely at direction of growth in a bivalve it will often gently spiral so that one side of the valve grows slightly faster than the other. Perhaps spiraling is part of being a MOLLUSC not just a ceph.

my :twocents:

J

I remembered reading an article for my thesis (oh, so long ago...) that might help here.

Sielacher, A. 1973. Fabricational noise in adaptive morphology. System. Zool. 22:451-465.

He basically said that information can be obtained from a skeleton on how that skeleton was formed, but that the clues to its fabrication are not in themselves necessarily an adaptive or a functional part of that organism.

Will be searching through old boxes this weekend for the paper.

"Constructional morphology" rather than functional morphology. My paleobio course spent a lot of time on this.

Going by the timeline that used to be featured on here, i don't think octopuses were closely related to ammonites at all, a segregation of the Bactritina occurring as far back as the Devonian. Personally I just think it's the fact that the coiled shell seems to be perhaps the most common shape of shell, certainly amongst molluscs. A coiled shell does make sense, as each new layer is secreted, naturally the body of the critter (in this case the argonaut) gradually moves around the outside surface of the shell.