Eyes as large as dinner plates

Discussion in 'Physiology and Biology' started by OB, Oct 29, 2005.

  1. OB

    OB Colossal Squid Staff Member Moderator

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    Yes indeed, but what do they see, our friends messie and archi? It is, to all intents and purposes, pitch black at hunting depth. Do they look for disturbances causing bioluminescence? They don't seem to prefer prey which has its own photophores... I recall one Architeuthis specimen being hauled in by fishermen, after they detected a large object on their sonar, hovering 5 meters over a school of hoki at an angle of about 45 degrees. Even if our squid overlords merely respond to fish swimming haphazardly into their clubs, they still need to know where to go in the first place. I now turn to the experts, is there any light left at 600-900 meters below? I was always taught that sunlight will not penetrate past 300 meters below sea level. I also know, however, that i.e. hatchet fish still employ countershading (reinforced by blue bioluminescence!), even at that depth.... I'm all confused now :confused:

    For certain, the recently photographed Architeuthis specimen had a strobe at its disposal.

    On a secondary note, do we know whether Architeuthis hunts both by day and by night? What do bycatch figures teach us there?
     
  2. Feelers

    Feelers Vampyroteuthis Registered

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    I have often wondered the same thing - instead of no eyes they have massive ones. Is there that much bio-luminescence down there?
    What do they see? Endless darkness? Graven images? It's all very confusing.
     
  3. OB

    OB Colossal Squid Staff Member Moderator

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    Well, there is a lot of bioluminescence down there, and, in all fairness, the less there is, the bigger eyes you need.
     
  4. monty

    monty Colossal Squid Staff Member Supporter

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    There's some interesting discussion of Architeuthis vision thoughts in this thread:

    http://www.tonmo.com/community/index.php?threads/3926/

    In particular, um... posted a wonderful reference on vision in the deep sea that discusses the intensity and nature of light at various depths, and a lot of biological issues about vision:

    http://www.tonmo.com/community/index.php?threads/3926/#post-57691

    good stuff!
     
  5. OB

    OB Colossal Squid Staff Member Moderator

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    Now that IS helpful :thumbsup:
     
  6. Feelers

    Feelers Vampyroteuthis Registered

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    I dont really understand the theory of bioluminescence - I understand small amounts such as the masking silhouettes from above, but I dont get how smaller organisms benefit from bright obvious bioluminescence. They can use it to attract food, but wouldnt this be just as or even more likely to attract predators? It seems like your dammed if you do and dammed if you dont!!

    If archyteuthis' eyes can't see any light from above then its diet would presumably consit of only bioluminescent organisms. Is this the case? I have no idea.


    How much light is at those depths? Is it 100% totally dark? or is there enough to be used for hunting?
     
  7. Jean

    Jean Colossal Squid Supporter

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    Many of them use species specific patterns probably for mate recognition (eg Lanternfish) others use it to attract dinner (eg anglerfish) some clever ones even have red coloured filters which turns the light they emit red which negates the protective red colouration that many deep water organisms have! Tis an area of study all on it's own!!!

    J
     
  8. OB

    OB Colossal Squid Staff Member Moderator

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    The staple food of Architeuthis is considered to be both benthopelagic (Nephrops, Eledone, macrourid fishes, possibly the orange roughy) and pelagic ( onychoteuthid, histioteuthid and ommastrephid squids, Trachurus, Micromesistius) and includes fast-swimming fish and squids.

    Hoki, the prey that keeps SOS' population occupied, don't "do" photophores, nor do patagonian toothfish, that in turn keep a vast population of Mesonychoteuthis happy.

    In order to detect prey, or prevent predation for that matter, under (assumed) zero light conditions, you'd need either sensitive motion sensors (i.e. lateral line in fish) or look for bioluminescence as a result of non-bioluminescent prey disturbing plankton in turn. You'll notice when studying deep water fish, that development of the lateral line in these is excellent. I'm not aware of squid having a similar system at their disposal...
     
  9. Jean

    Jean Colossal Squid Supporter

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    Tis possible tho' Bernd Budelmann reported on what appeared to be a similar system on the head and tentacles of cuttlefish

    Budelmann BU, Bleckmann H. 1988. A lateral line analogue in cephalopods:
    ... Trans. R. Soc. Lond. B. 315:305–343.

    Sorry can't remember the rest of the title!

    It's moot point whether or not it exists in the Messies and Archies but I guess it is possible!

    J
     
  10. Feelers

    Feelers Vampyroteuthis Registered

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    Just read up about the lateral line thing, very interesting.

    So much of the plankton down there is bioluminescent too? I remember being told ( at school) that there wasnt really any plankton below 10m!!
     
  11. Jean

    Jean Colossal Squid Supporter

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    No PHYTOplankton certainly but lots of zooplankton (quite a bit of the deep scattering layer is thought to be zoo plankton!) :grin:

    J
     
  12. OB

    OB Colossal Squid Staff Member Moderator

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    Just looked up the article in question via pubmed, here's the publicly available bit:

    J Comp Physiol [A]. 1988 Nov;164(1):1-5. Related Articles, Links

    A lateral line analogue in cephalopods: water waves generate microphonic potentials in the epidermal head lines of Sepia and Lolliguncula.

    Budelmann BU, Bleckmann H.

    Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77550.

    Many cephalopods have lines of ciliated cells on their head and arms. In the cuttlefish Sepia and the squid Lolliguncula, electrophysiological recordings clearly identify these epidermal lines as an invertebrate analogue to the mechanoreceptive lateral lines of fish and aquatic amphibians and thus as another example of convergent evolution between a sophisticated cephalopod and vertebrate sensory system. Stimulation of the epidermal lines with local water displacements, generated by a vibrating sphere, causes receptor potentials that have many features known from lateral line microphonic potentials. The minimal threshold of the head lines is 0.2 micron peak-to-peak water displacement (calculated at the skin surface) at 75-100 Hz.

    PMID: 3236259 [PubMed - indexed for MEDLINE]

    Don't you just LOVE the internet!
     
  13. Jean

    Jean Colossal Squid Supporter

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    Oh Yeah! What did we do before it!!! :lol:


    j
     
  14. OB

    OB Colossal Squid Staff Member Moderator

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    WRT the original thread title: this seems to be an oldy but a goody, anyone for date and location? It looks fifties,sixties or seventies to me and it could well be Tasmanian (comes off a Taz newsletter...), but I'm definitely not sure about either... Absolutely HUGE eye, check the mackerels for size! Crumb from the sperm whale table?
     

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