Argonauts

Discussion in 'Physiology and Biology' started by Phil, Mar 26, 2004.

  1. Phil

    Phil Colossal Squid Supporter Registered

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    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?
     
  2. Burstsovenergy24

    Burstsovenergy24 Larger Pacific Striped Octopus Supporter

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    Never heard of them, but now youve sparked my interest! So the shells look like this?
     
  3. NickA5582

    NickA5582 Sepia elegans Registered

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  4. neptune

    neptune Haliphron Atlanticus Registered

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    They are amazing!!

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

    fluffysquid Vampyroteuthis Registered

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

    Architeuthoceras Architeuthis Staff Member Moderator

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    Location:
    somewhere under the desert sky
    Aint those the guys what sailed with Jason, after the golden fleece?

    Dr. Woods posted this site on the Ceph list.
    Argonauts

    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.
     
  7. Phil

    Phil Colossal Squid Supporter Registered

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    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
     
  8. cthulhu77

    cthulhu77 Titanites Supporter

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    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:
     
  9. Architeuthis

    Architeuthis Pygmy Octopus Registered

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

    Argonautautidae Cuttlefish Registered

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    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.
     
  11. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    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
     
  12. Argonautautidae

    Argonautautidae Cuttlefish Registered

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    Hi Steve,

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

    Michael.
     
  13. Argonautautidae

    Argonautautidae Cuttlefish Registered

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    Argonauta photos

    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.
     
  14. Burstsovenergy24

    Burstsovenergy24 Larger Pacific Striped Octopus Supporter

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    8) Awesome pics.


    Might I suggest a quarter for reference? :)
     
  15. Argonautautidae

    Argonautautidae Cuttlefish Registered

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    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. :)
     
  16. Argonautautidae

    Argonautautidae Cuttlefish Registered

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    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.
     
  17. cthulhu77

    cthulhu77 Titanites Supporter

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

    Phil Colossal Squid Supporter Registered

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    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
     
  19. Argonautautidae

    Argonautautidae Cuttlefish Registered

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    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.
     
  20. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    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

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