How is stomach content analysis of squid done?

Discussion in 'Physiology and Biology' started by chrono_war01, Jun 12, 2008.

  1. chrono_war01

    chrono_war01 Colossal Squid Supporter

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    Kind of urgent-ish, I'm doing something for my diploma course and I'm supposed to write a paper on something biology related and I'm probing into the possibility of doing a squid stomach content analysis. However, if memory serves well, squids tend to mash their food into very small bits rendering content IDing somewhat hard to do.

    So, if anyone can give me a in-depth explanation on how stomach content IDing for squid is done, it'd be greatly appreciated.

    Thanks,
    Chrono (Eric)
     
  2. Tintenfisch

    Tintenfisch Architeuthis Staff Member Moderator

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    Hi Eric,

    It's a fiddly and frustrating business. Jean has done more than I have and I'm sure she can offer some additional info, but basically you have to (1) find (a) squid(s) with anything IN the stomach caecum (problematic for the larger squids in particular - Architeuthis is almost invariably empty); (2) empty out the entire caecum, sort through every tiny little piece of crud you find, and set aside the few fragments that can potentially be identified; and then (3) try to identify them. You're right that squid chop everything up into tiny pieces. If the squid's been eating fish, your most identifiable pieces tend to be scales, bones (sometimes verterbrae) and eye lenses, which aren't much to go on. If it's been eating other squid you may get an arm fragment (potentially helpful if the suckers/hooks are in good condition), a buccal mass (also good - beaks, radula), or most usefully a piece of tentacle. Sometimes the soft parts aren't completely bitten into separate pieces, but rather chopped into a series of chunks that stay connected as they're swallowed - I've seen whole tentacles like this in stomach caeca.
    Another tough thing about it is that squid digest pretty fast, so unless the squid is caught with a full caecum, killed and and preserved immediately, there won't be much recognizable in there.
     
  3. Jean

    Jean Colossal Squid Supporter

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    Kat's pretty much covered it all.....(Eric check your pms) I have found lone otoliths in an otherwise empty caecum!

    J
     
  4. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    An alternative technique to reconstruct diet involves fatty acid signatures; do a google.scholar search on George Jackson & fatty acids; you'll find a few pdfs readily available.
     
  5. Keith

    Keith Vampyroteuthis Registered

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    man i wish i still had one of my papers from the JC i was goin to. i did something similar in an advanced bio class after we disected squid. bummer.
     
  6. Jean

    Jean Colossal Squid Supporter

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    If you get stuck I have some of those, if not all.

    J
     
  7. chrono_war01

    chrono_war01 Colossal Squid Supporter

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    Thanks for all the help, but on a rather unfortunate note, I've spoken to my Biology teacher and the potential possibility of me doing a related topic was dashed due to it being "unimportant" and the topic being not able to be put into a question format.

    Utter nonsense, I know. Wasted my entire day dissecting squid and looking for the bloody stomach.
     
  8. Keith

    Keith Vampyroteuthis Registered

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    bummer. thats weak.
     
  9. Jean

    Jean Colossal Squid Supporter

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    Really? Your teacher sounds a bit blinkered! what it probably means is that your biology teacher wouldn't be able to mark it because he or she knows nothing about the topic!

    Question: Are squid opportunistic predators or do they target specific prey types?

    Importance: squid fisheries can be worth up to $1 billion in a good year, squid are often "keystone" species in oceanic food webs!

    Seems your teacher doesn't really want to encourage independent thinking!

    J
     
  10. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    :shock:

    What do squid eat, what eats squid? Remove the squid (fisheries) and watch the cascading effects through food chains to the good-old charismatic megafauna (sea birds, teuthophagous cetaceans, fish); just check out Matt's article to see what could happen (decrease in squid in the diet and corresponding increase in fish and crustaceans to compensate for it), or this (and there's another in the articles, report # 2) for long-finned pilot whales. Fish down the food chain (krill, as is occuring now) and see what the cascading effects are through food chains. Remove the fish (fisheries) and see what niche is opened up, and what the likely effects of this might be (good, old cascading effects again) - if we don't know what the squid eat we have no idea what the cascading effects might be. Global warming, expansion in the range and abundance of certain fish and/or squid species (example being Humboldt), and see what the effects of this might be on food chains! It even depends on how we fish for squid!! My word. I realise that I am preaching to the converted, but everything is integrated.

    I don't want to speak ill of your teacher at all; they might have your best interests at heart, but you could direct them here and we'd have a nice chat with them as to the importance of this work, its applied nature, and how we could best fit it into a hypothesis driven research project (most theses/research programmes these days are required to be hypothesis driven, EXCEPT ANYTHING TO DO WITH ME! I have this argument weekly with folk around here and am tired of banging my head against walls).

    Give us one minute of our collective time with your teacher and I'm sure that we'd convert them! It is just as applied and conservation-oriented as any subject, and as far as I am concerned, far-more important!
     
  11. monty

    monty Colossal Squid Staff Member Supporter

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    :notworth: :grad: :oshea:
     
  12. Keith

    Keith Vampyroteuthis Registered

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    well said monty
     
  13. Jean

    Jean Colossal Squid Supporter

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    HEAR HEAR! I note Steve, that it's part of the NZ high school science curriculum that students have to be able to prepare an hypothesis, test and discuss the results........no-where is there any leeway for curiousity based science......the wonder what would happen if........or.....the wonder what the fuzzwart fish eats type research.

    Sad really it takes all the wonder out of science!

    J
     
  14. bathypol

    bathypol Wonderpus Registered

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    If you are still curious, there is a paper about Northern Bottlenose Whales and Gonatus fabricii which is worth checking out (Hooker, et al, 2000 - I beleive). It deals with both stable isotopes and fatty acid analysis in relation to predator/prey interactions.

    On a related note, does anyone know of a good crustacean identification guide? I have quite a few squid with full stomachs and have a lot of intact pieces of exoskeleton...it would be nice to know what they :)

    Cheers.
     
  15. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    Check out the Challenger or Discovery Reports; lots of pics.
     
  16. bathypol

    bathypol Wonderpus Registered

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    thanks :smile:
     

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