Purty Molluscs

Discussion in 'Physiology and Biology' started by um..., Sep 26, 2003.

  1. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    To make a short story long...

    I got my hair cut today, which is something I loathe even more than having my teeth cleaned. (While the results are wonderful in both cases, there's just something awfully disturbing about trying to sit still while sharp/pointy objects are being applied to bits of my head.) As I was waiting for my turn in the chair, I was trying to think of interesting things not to talk to the hairdresser about. (Where did all the barbers go?) While I was staring vacantly at a picture of some lovely model with some lovely haircut vacantly staring back at me, I hit upon chromatophores as a suitable topic to concentrate on while I was being tormented for the next 20 minutes. It was the model's makeup. It occurred to me that chromatophores would be an absolute godsend to most of the women I know. Think of the time, money, and frustration (mostly incurred by male companions) that could have been saved, if only the vagaries of evolutionary pressure had so allowed. (BTW, what's the deal with eyeshadow? :yuck: ) So here's what's been bothering me:

    How did cephalopod chromatophores evolve? Are there any good theories or studies that indicate how this might have happened?

    I'm having a hard time convincing myself of a plausible way around that "irreducible complexity" bunk.
     
  2. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
  3. Jean

    Jean Colossal Squid Supporter

    Joined:
    Nov 19, 2002
    Messages:
    4,215
    Likes Received:
    133
    Location:
    Dunedin, New Zealand
    I actually think it was a con job by the male of the species! If you look at most other species it's the MALE who gets all gussied up to attract a mate, somewhere along the line we got conned into putting that gunk on our skin for you fellas to admire(?)

    BTW yes I DO have some eyeshadow & if you give me a year or so I may even remember where I put it...........don't wear it much (ever!) course that may be why I'm footloose & fancy free at the moment, that and the fact I have no life (the thesis thingy!) and often smell of eau d' squid! :lol: :lol: :lol:

    J
     
  4. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    Such is the price of enforcing monogamy (which I happen to prefer, since the alternative seems like too much damned work :D ). Shall I launch into my rant about De Beers? :x


    Mmmmm, eau d'squid... :yuck:
     
  5. Jean

    Jean Colossal Squid Supporter

    Joined:
    Nov 19, 2002
    Messages:
    4,215
    Likes Received:
    133
    Location:
    Dunedin, New Zealand
    If you like, personally, I prefer saphires!


    J
     
  6. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    Shall I launch into my rant about saphires? :)
     
  7. Jean

    Jean Colossal Squid Supporter

    Joined:
    Nov 19, 2002
    Messages:
    4,215
    Likes Received:
    133
    Location:
    Dunedin, New Zealand
    Sure, but I'll ignore you!!!!! :D :D (Anyhow I buy my own saphires! :( )

    J
     
  8. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    All this talk of sparkly things reminds me of something...

    I think my question should be expanded to encompass the evolution of cephalopod body patterning from a holistic point of view. (Does anyone even care? I'm going to turn this thread into a blog, eventually.) Doesn't the efficacy of chromatophores in crypsis/communication depend on the distribution of reflecting cells, iridophores, and leucophores? Does it make sense to inquire about the evolution of chromatophores in isolation?

    I'm assuming that the whole papillation(?) issue can be studied separately from colouration. Does that make sense?

    Enough questions. I'm going to :beer: :beer: :beer: ... :sleeping: now.

    Avast! There be new smilies in the hold: :arr: I'll be raisin' a cup 'o me finest grog ta salute the beauties (sorry, Phil) that painted these! Arrrrr!
     
  9. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    BTW; thanks, Jean, for being the only person to reply to this thread. As for you hundred (or so) others...

    :P
     
  10. tonmo

    tonmo Titanites Staff Member Webmaster Moderator

    Joined:
    May 30, 2000
    Messages:
    8,672
    Likes Received:
    489
    Location:
    Pennsylvania
    Well I think these are good questions... in fact I promoted them in the newsletter last week!

    Tough ones though... evolution of chromatophores... Have you seen this one?

    Shells are often seen as a major contribution to the success of molluscs. Why, then, have many molluscs lost or reduced their shells?

    Talks about how the shedding of shells led to the evolution of chromatophores.

    That's from Andrew Gray, not to be confused with Andrew Packard from one of your excellent links up there...

    I would think so!
     
  11. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    Great link, Tony! That subject could use its own thread...

    Loss of the shell, not to mention coevolution with fish, is clearly going to be important in the evolution of body patterning. So we're looking at something like 350 million years (Phil?) of evolution, which is a heck of a lot of generations for animals with such short lifespans. Plenty of opportunity for all sorts of crazy adaptations. Hmmm....

    What I've been looking for, most recently, is some kind of investigation into how chromatophores develop in embryonic cephalopods (feeling out the "Evo-devo" angle). Such information is proving very hard for me to find. Any marine biologists out there care to suggest a better method of searching than Google?


    :confused:
     
  12. Jean

    Jean Colossal Squid Supporter

    Joined:
    Nov 19, 2002
    Messages:
    4,215
    Likes Received:
    133
    Location:
    Dunedin, New Zealand
    Interesting the comment that deep sea cephs could get there because they had no shell, Packard (1972) went with the opposite, because the cephs went deep they lost their shells due to increased hydrostatic pressure and then some of the shell-less beasties recolonised the shallow water! I think this is one of those chicken & egg questions! Another one is did the chromatophores develop before the good eyesight or did the eyesight develop because the cephs needed to be able to see the patterns in their school mates :bugout: It's interesting that Nautilus with relatively poor eyesight has no chromatophores!

    J


    Reference: Packard, A. 1972 Cephalopods and fish: The limits of convergence Biological Reviews vol 47, p. 241-307
     
  13. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

    Joined:
    Nov 19, 2002
    Messages:
    4,668
    Likes Received:
    17
    .... well, they haven't exactly 'lost' their shell, it's just been internalised in most cephs.

    Cirrate (finned) octopods still retain a shell (internalised, variably U-, V-, W- or saddle-shaped); Vampyroteuthis has that bizarre shield-shaped vestige; squid still retain the gladius in most (although things like Sepioloidea completely lack a gladius/pen/shell); many benthic octopodids (Octopus and kin) still retain a shell vestige, in the form of dorsal stylets embedded in musculature inside the mantle, in some the stylets are calcareous; Spirula still has a calcareous shell .... and of course there's Nautilus. In non-nautiloids, as a rule the shell has been reduced and internalised, with secondary development in the likes of Argonauta.

    ... but evolution of chromatophores ..... hmmmm.
     
  14. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    I'm sure I don't really know what I'm talking about, but Packard's scenario seems less likely to me. Perhaps I'll change my mind when I actually read what he has to say.

    Interesting. Narrow-minded fella that I am, I had assumed body patterning evolved primarily for the purpose of crypsis, with communication being an exaptive(?) development. Now I'm thinking that it might make a lot more sense if it were the other way 'round. It seems to me that crypsis would require a much more complete system to be effective, whereas even primitive stages in the evolution of body patterning could be useful for display/communication.
     
  15. Bald Evil

    Bald Evil Cuttlefish Registered

    Joined:
    Apr 3, 2003
    Messages:
    29
    Likes Received:
    0
    I was wondering if there are any known cephalopods with chromatophores that emit light frequencies outside the visual spectrum. It may be fanciful, but the notion of deep sea cephalopods using short wavelength light emitted from chromatophores as a type of active or passive lidar is appealing to me. I suppose the biggest problem would be the difficulties light has in traveling through water, but if a cephalopod's eyes were adapted to compensate for the diffusion and refraction of deep water, it would make for a very effective detection system. I guess I'm supposing that some cephalopods could evolve (or could have evolved) to use their eyes and chromatophores the way bats use their ears and echolocating sonar. Nature has come up with stranger ideas!

    I know this isn't really about how chromatophores evolved, but the 'why' of evolution often answers the question of 'how'. :)
     
  16. Phil

    Phil Colossal Squid Supporter Registered

    Joined:
    Nov 19, 2002
    Messages:
    3,034
    Likes Received:
    16
    Evolution of chromatophores? Well, I’ve had a bit of a think about this and I think that these were a development of the earliest coleoids. I’ll tell why I think this is, but please feel free to shoot me down in flames if you wish! Fossil coleoids, excluding belemnoids, are very rare due, of course, to their soft bodied nature. There do not appear to be many researchers working on them at present and doubtless with one or two future discoveries the whole working system will have to be reworked. Anyway…….

    I think the key to this lies with Vampyroteuthis. The Vampire squid is the only surviving member of the Vampyromorpha that we know of. The Vampyromorpha were an incredibly ancient lineage, recent cladistic analyses such as the one available here indicates that the Vampyromorphs were at the root of one of the two main branches of the coleoids, the other being the belemnoid families which split from a common ancestor probably in the early Carboniferous sometime around 350mya. Most of the fossil ‘squid’ that one sees depicted from deposits such as the later Jurassic Solnhofen were members of the Vampyromorphs.

    It is believed that these Vampyromorphs and the lineage that led to the modern squid, and cuttlefish, split from a branch soon after this initial divide from the ancestral coleoid, with the modern Spirula representing a comparatively unmodified ancestral form. It is believed that this split into the modern squid and cuttlefish probably happened in the early Tertiary, following the massive Cretaceous marine extinctions. The octopus lineage is thought to have split sometime in the Jurassic from the Vampyromorpha, the earliest known example being Proteroctopus ribeti (160mya)

    What has this to do with chromatophores? Well, according to cladistic analyses Vampyroteuthis, the modern squid, cuttlefish and octopus all appear to have had a common ancestor that lived in the early Carboniferous and all these groups have modern examples that demonstrate chromatophores. Unless it is conceivable that chromatophores evolved independently in all these groups, which seems unlikely, it seems at least a strong possibility that the common ancestor of all these groups would have possessed chromatophores at a date of around 350mya. This ancestor had only comparatively recently split from the initial branch in the coleoids in the late Devonian. Perhaps one could speculate that possibly the belemnoids would have possessed chromatophores too, if the common ancestor of both groups had possessed them. (Practically impossible to prove though!).

    Vampyroteuthis does have chromatophores though they have weak musculature. To quote from the Tree of Life pages:

    “These chromatophores, however, have lost the muscles that enable rapid color change in other coleoids and are probably incapable of changing shape. A few normal chromatophores associated with photophores are still present.”

    This is probably an adaption to life in the abyss; who needs a colourful display in the dark? Early Vampyromorphs were certainly not all deep water animals. The recent discovery of an Upper Cretaceous animal from Japan that has been named Provampyroteuthis giganteus is believed to have swum in the surface waters and was much bigger than the modern Vampyroteuthis. Living in an off–estuary environment it is quite possible that this animal had developed chromatophores to a higher degree than its modern descendant. Fossils of this animal have been recovered from stomach contents of Elasmosaurid plesiosaurs; these were believed to be surface or shallow water swimmers. (I can print the reference for this if anyone wants to follow it up).

    I’m sure that I have managed to make something comparatively simple much too complicated. This stuff is so much easier with a diagram and timeline, you know!

    :vampyro: :bonk:
     
  17. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    While I'm not able to answer that question, I do know of a few species of fish (e.g. Pachystomias microdon) that use red light from photophores under their eyes as a kind of searchlight to locate prey. Many of the animals in the deep sea, as far as I know, cannot see red light since virtually none penetrates to any significant depth. Is this the sort of thing you had in mind?

    That's sort of how I look at it. The 'how' of it is a series of steps, and each step answers a 'why'. I hope this thread touches upon various aspects of ceph body patterning and photophore use, not just the evolution of chromatophores. I don't think that question can really be answered, but hopefully it'll lead to other interesting questions and observations (like yours).
     
  18. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    Please do!

    I was hoping you'd weigh in with something like this. :D

    Must digest...
     
  19. Phil

    Phil Colossal Squid Supporter Registered

    Joined:
    Nov 19, 2002
    Messages:
    3,034
    Likes Received:
    16
    Here you go!

    Kanie, Y., Hasegawa, Yoshikazu, Okazaki, Y. and Tatematsu, Yoshiko; 1998:

    Vampyromorphs: past and present; - Cretaceous vampyromorph (Coloidea: Cephalopoda) as the diet of a plesiosaur; Bulleton of Gunma Museum of Natural History (Number 2) pp: 11-23

    If anyone tracks this down , please let me know! Providing it's not all in Japanese, of course. :D
     
  20. um...

    um... Architeuthis Supporter

    Joined:
    Sep 5, 2003
    Messages:
    1,968
    Likes Received:
    0
    I have just discovered a wonderful article:

    Messenger JB (2001) Cephalopod chromatophores: neurobiology and natural history. Bio Rev 76: 473-528

    I have yet to actually read any of it, but it appears to be fairly comprehensive (for its length).

    5 pages of references. Hooray! More bloodshot eyes!
     

Share This Page