Is Loligo Ammoniacal? | The Octopus News Magazine Online
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Is Loligo Ammoniacal?

monty

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#1
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.)
 

Steve O'Shea

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#2
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).
 

monty

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#3
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.
 

cuttlegirl

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#4
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.
 

cthulhu77

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#5
"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.
 

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