Is Loligo Ammoniacal?

Discussion in 'Physiology and Biology' started by monty, Oct 25, 2007.

  1. monty

    monty Colossal Squid Staff Member Supporter

    Joined:
    Mar 8, 2004
    Messages:
    4,887
    Likes Received:
    11
    I was reading a bit of J. Scott Turner's The Tinkerer's Accomplice last night that brought up using ammonia for buoyancy in squids (which was great, more popular science books need to discuss comparative buoyancy in Cephalopods) but I was surprised that Loligo was brought up as the ammoniacal squid example; I thought Loligo was non-ammoniacal and negatively buoyant... I can't find a good reference except a paper in a journal I don't have access to; anyone got

    Voight J.R., Portner H.O. and R.K. O'Dor 1994. A review of ammonia-mediated buoyancy in squids (Cephalopoda: Teuthoidea). Marine and Freshwater Behaviour and Physiology. 25 : pp.193-203

    handy? Or just know the answer and want to tell me?

    I had thought that most squids we humans can eat are negatively buoyant and just have to swim a lot (although I seem to remember from Dr. Gilly's TONMOcon I talk that Dosidicus gigas is "seasonally ammoniacal" in that it's inedible from ammonia some times of year but not others.)
     
  2. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

    Joined:
    Nov 19, 2002
    Messages:
    4,668
    Likes Received:
    17
    I wouldn't have thought so Mark .... but I've never looked at Loligo (being a genus often eaten I cannot imagine it to be ammoniacal, but I don't want so say so, emphatically, because I cannot say that I've studied it and am any wiser than the original author).
     
  3. monty

    monty Colossal Squid Staff Member Supporter

    Joined:
    Mar 8, 2004
    Messages:
    4,887
    Likes Received:
    11
    Since Scott Turner sent me a nice letter when I praised his book elsewhere, I asked and he confirmed that this was a mistake in his book (although his description of ammoniacal buoyancy in squids is accurate, and his interpretations are interesting.) It's curious that I couldn't find a definitive list anywhere on the internet of which squids do or don't use ammonia for buoyancy.... I would think it's relatively easy to test for, although I guess Dosidicus gigas is seasonably edible or not (at least in the Sea of Cortez) which might be related to ammonia levels in the tissue, so for them the answer is "sometimes." I wonder if Dr. Gilly or anyone else is studying that... It seems weird that the squid's buoyancy needs would fluctuate seasonally... I wonder if there's some sort of tradeoff that when food is scarce, being ammoniacal is good in that the squids have to spend less energy to stay at their preferred depth, but when food is plentiful, it's an advantage to have strong muscles for hunting even if that means there's more effort required to "just keep swimming, just keep swimming" to avoid sinking.

    By the way, I highly recommend his book The Tinkerer's Accomplice (J. Scott Turner is how he's credited) as food for thought about why, even though Darwinian processes are not goal-directed, phenomenologically many things we observe in organisms appear designed, intentional, or teleological.
     
  4. cuttlegirl

    cuttlegirl Colossal Squid Supporter Registered

    Joined:
    Sep 16, 2005
    Messages:
    4,891
    Likes Received:
    236
    Location:
    Pittsburgh, PA
    Hmm, as always, Monty, you make me come up with more questions than answers...

    I wonder if seasonal ammoniacal levels are related to the prey that is eaten seasonally or if it is related to their sexual maturity. Maybe having lots of large eggs in the ovary makes them negatively bouyant and they need the ammonia to counteract this.
     
  5. cthulhu77

    cthulhu77 Titanites Supporter

    Joined:
    Mar 15, 2003
    Messages:
    6,642
    Likes Received:
    2
    "gotta go, I gotta go"...the reason for high ammonia levels. No portable cans in the ocean.

    (joking, jeez)

    I did a series of black and white illustrations for a prof up at NAU waaaay back when, and had to dissect quite a number of loligo...zip ammonia smell. They were cut up over a two semester period, so I think I got a good crossection (pardon the pun) of them at that time. Of course, that was back in the early 80's, when fish was still safe to eat also.
     

Share This Page