wikipedia "giant squid" article needs fixing

[monty]

This got my attention earlier, and something about it kept ringing in my head. So I spoke to my friend Thomas about the distribution of ammonium ions in this squid, and he advised me of something which I had long forgotten.

Ammonium ions in solution (NH4+) are a by-product (waste) of protein metabolism and are highly toxic. Yeah, I know - "duh"- but bear with me here. By its nature, its a weak base, and emulsifies lipids into soaps through saponification. It also does this to phospholipids (think cell walls) so accretion of this ion in the system is a bad, bad thing. So a case can easily be made for specialized, ammonium-resistant vacuoles, or the squid muscles would suffer massive reduction damage by such ions. Vacuoles would be EXTREMELY hard to detect. Maybe something chemical in the endoplasmic reticulum?

Just my two cents.

John

Yeah, that certainly sounds like it would be a serious problem for cell walls, and that's fundamental enough that it's unlikely that Archi membranes evolved to somehow tolerate NH4+. So, I guess the question is scale-- are there intracellular vacuoles, or some sort of pockets lined with some protective sheath embedded in the flesh? I still also wonder how much active control there is in getting the ratios right for neutral buoyancy, too-- is there a fixed amount of "negative weight" from the ammonium chloride, or is there some active system that's moving it around (maybe it's re-routed from the excretory system into wherever it's stored?) I thought for a minute that if archi kept its density close to neutral, the squid could tense up muscles and become a little denser to sink, and relax to float, too, perhaps, but then I remembered that mollusk muscle can be thought of as a "muscular hydrostat" which conserves volume and mass, so it can't change density, just shape.... hmmmm....

 

[Fujisawas Sake]

Well, I would imagine that the ammonium chloride breaks down into constituent ammonium and chloride ions in solution anyway, given that NH4Cl is pretty soluble in water.

Maybe the issue is analogous to turtle anoxia. Certain turtles overwinter in ponds, and since some of these ponds freeze, the turtle is trapped underwater for some time. Given that their metabolic rates slow immensely, and gas exchange occurs through the cloaca, the major issue here is a buildup of Carbon Dioxide and resultant carbonic acid. Turtles use the bones of the shell as a "carbon sink" and therefore can tolderate several months' worth of CO2 buildup without suffocating.

Now, maybe there is an extensive mod of the Archi's excretory system that can serve as an ammonium sink. They use pretty well-developed metanephridia, but... Hmm...

Wait one second!! The major ion concentration gradient is in the mantle, right? Fish use their passive and active diffusion across their gills as a way to excrete excess ammonium and other ions, right? Do the ctenidia of Archis also serve such a function? Such a convergence with fish would not be out of the question. It just seems that continuous ion-pumping would get to be pretty metabolically costly for an animal that lives as an ambush predator. Then again, its not like its hunting gazelles on the Serengeti.

Wow, we really don't know much about these animals, do we? Gosh, as much as I hate to say this, it might be easier to find a related species, do some experiments on it, and extrapolate from that.

Just my two cents.

Sushi and Sake,

John

 

[monty]

Well, I would imagine that the ammonium chloride breaks down into constituent ammonium and chloride ions in solution anyway, given that NH4Cl is pretty soluble in water.

Maybe the issue is analogous to turtle anoxia. Certain turtles overwinter in ponds, and since some of these ponds freeze, the turtle is trapped underwater for some time. Given that their metabolic rates slow immensely, and gas exchange occurs through the cloaca, the major issue here is a buildup of Carbon Dioxide and resultant carbonic acid. Turtles use the bones of the shell as a "carbon sink" and therefore can tolderate several months' worth of CO2 buildup without suffocating.

Now, maybe there is an extensive mod of the Archi's excretory system that can serve as an ammonium sink. They use pretty well-developed metanephridia, but... Hmm...

Wait one second!! The major ion concentration gradient is in the mantle, right? Fish use their passive and active diffusion across their gills as a way to excrete excess ammonium and other ions, right? Do the ctenidia of Archis also serve such a function? Such a convergence with fish would not be out of the question. It just seems that continuous ion-pumping would get to be pretty metabolically costly for an animal that lives as an ambush predator. Then again, its not like its hunting gazelles on the Serengeti.

Wow, we really don't know much about these animals, do we? Gosh, as much as I hate to say this, it might be easier to find a related species, do some experiments on it, and extrapolate from that.

Just my two cents.

Sushi and Sake,

John

Hmm.... this is starting to get out of my league biochemistry-wise (mortal fear of organic chem and the like is the main reason I didn't try for a double major in biology). I noticed that there are a number of papers in cephbase on the ammonia secretion mechanisms in cephs (presumably mostly the ones that don't use it for buoyancy) but I didn't look at them closely.

Wouldn't the hypothetical ammonium sink have to be distributed around the body of the squid in roughly the same distribution as Steve found the ammonia concentration, rather than being confined to the excretory apparatus? Or are you saying that perhaps the storage developed in the excretory system at first, but then a mutation allowed it to be expressed in muscle tissue (hence everywhere) and that provided the very favorable neutral buoyancy property so it caught on?

My source for thinking the ions are in the form of Ammonium Chloride (presumably in solution, as you say) is from a short mention in Wells & O'Dor "Jet Propulsion and the Evolution of the Cephalopods" from Bull Marine Science 49(1-2):419-432 1991:

Where coleoids have, for one reason or another, returned to life-styles that would benefit from neutral buoyancy, they have generally achieved this by replacing sodium with ammonium chloride, a mechanism that leads to rather flabby animals but which, unlike the gas-filled shell, is not limited by implosion depth (Clarke et. al. 1979).

Clarke et. al. sounds like it may be similarly enlightening to the journal that's missing its online form:

Clarke, Denton, and Gilpin-Brown, "On the use of ammonium for buoyancy in squids," J. Mar. Biol. Ass. U.K.: 59 259-276

Weirdly, it's not in cephbase. It's also not in the Caltech or U of California library systems database (the whole journal, in fact!). Steve refers to it in his archi buoyancy article in the TONMO science section, too.

So I guess people have studied this, but only published it in hard-to-find places...

 

[Steve O'Shea]

Weirdly, it's not in cephbase. It's also not in the Caltech or U of California library systems database (the whole journal, in fact!). Steve refers to it in his archi buoyancy article in the TONMO science section, too.

... a long time ago I was approached and asked to submit hard copies of my papers to cephbase; I didn't as I was led to believe that they only cite articles that they have a copy of (or some such thing) online. I thought that a little rank. Accordingly countless squillions of papers are not cited on cephbase, simply because they haven't got copies in a personal library!!

I don't think that that is an appropriate service; I thought it more a means of freely developing a library for a limited few.

 

[Steve O'Shea]

"There are now ~5900 ceph papers in our reference database, including 33 papers published in 2004, 119 papers published in 2003, 161 papers published in 2002 and 1103 references in pdf format, available for download. Currently, we are only able to sporadically enter new papers into the database. Please send reprints to Catriona Day, Fisheries Centre, Lower Mall Research Station, 2259 Lower Mall, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4 and email pdfs to cephbase @ hotmail.com. Reprints and pdfs we receive will be added to CephBase in time but there may be considerable delays. Thank you for your patience."

 

[monty]

This is helpful-- I guess for some squids (not specificially architeuthis) there are vacuoles in the muscle mass (there's an overview in the introduction...)

http://academic.evergreen.edu/t/thuesene/seibeletal2004.pdf

 

[Fujisawas Sake]

Monty,

You're preaching to the choir about orgainic chem. Personally, I didn't like the course because most teachers don't seem to like teaching it. And its relevance to modern biology is treated as nearly nil, when the exact opposite is true. But as a subject, its bloody brilliant and fascinating.

Anyway, I figured ontogeny would be a factor here. Steve-O indicated that giant squid were found at different levels of the water column at different stages of their lives, so it would make sense that whatever triggers the storage of ammonium in the system (regardless of structures) occurs as the squid develops.

The quote by Clarke et al made me wonder; if ammonium ions are used in place of sodium, in which functions are they replaced? Also, ammonium ions are 18 amu's (atomic mass units), while sodium are 23 amu's. Are five amu's really enough to affect neutral buoyancy? Maybe there's a chemical property in how the ammonium ions are used as well as their weights. Considering that ammonium ions and hydroxide ions (OH-) form a weak base, while sodium is a reactive metal (and strong base when fused with free hydroxide), there would be a markedly different reaction when these are utilized by a living system. I have to read these papers. However, what do they mean by "mechanism" which "leads to flabby bodies"? Molluscs are soft-bodied by nature! Its a main feature of the phylum! I need to read this paper before I make any generalization or conclusion, but this phrasing was a little odd.

So, Steve... Sound like any good project ideas?

John

 

[Fujisawas Sake]

Okay, went back to my physio. textbook and checked some info.

AMMONIA (NH3) is a metabolic waste compound produced in most marine invertebrates. Nasty stuff there; it passes easily through cell membranes and is highly toxic to cells. However, when presented with a free proton (H+), it becomes the ion NH4+, or ammonium. This is called diffusion trapping. Cell membranes use charged protein "gates", which repel ammonium to a cerain degree. However, ammonium ions are still toxic and must be either excreted as ammonia through changing ammonium to ammonia, amination (the act of adding an amine to the ammonuim ion), or by storage. The first two are metabolically costly processes. The last is storage by conversion to a less toxic, more easily stored material like glutamine. Fish do this.

Ammonium, while being less toxic, still affects neurotransmission at the postsynaptic level. Ammonia is deadly and must be excreted. Hmm...

Maybe this also has to do with the pressure and properties of water at the midwater levels. Ammonium excretion is an active process, and maybe its a lot harder to excrete ammonium and ammonia in the depths at which the adults live, so subsequent buoyancy my have evolved as a side-effect of the need for ammonium storage. Such a welcome mutation could have been the cause of the Archi's lifestyle. Who knows?

John

 

[Steve O'Shea]

... we don't know if the subadults/juveniles are ammoniacal.

 

[Clem]

Ammonium, while being less toxic, still affects neurotransmission at the postsynaptic level. Ammonia is deadly and must be excreted. Hmm...

Hmm...is right, John. Don't squid axons have some odd ability to neutralize "nerve gas" compounds? The de-toxifying agent is an ion called isethionate, (good thing I had the Ellis book out for crypto-zoo references, as he's also got a section about the odd enzyme), "an alcohol molecule with sulfonic acid at one end." Would isethionate react with ammonium in any meaningful way?

Clem

 

[Fujisawas Sake]

Would isethionate react with ammonium in any meaningful way?

Clem

I don't think so, given that acids donate protons and adding another H+ to NH4+ would be HARD.

What are the coping mechanisms for other ammoniac squid? Are there some that we haven't mentioned yet?

John

 

[monty]

Wikipedia accuracy

It is my contention that this sentence from
Giant squid - Wikipedia
is complete nonsense:

However, it is thought to be impossible for a giant squid to lift its tentacles from the water.

Since I removed it once, and one of the editors put it back, I'd like to get confirmation from you architeuthologists that it's pretty bogus. Of course, since Architeuthis is generally not at the surface at all, and no one has seen it alive and healthy, there's no way to know this, but from what I know about cephalopods, they're pretty strong in general, and only the most gelatinous of deep-water cephs seem like candidates for not being able to lift their own arms without help from bouyancy.

Obviously, I'm pretty sure about this, I just would like "ammo" from known experts to wave in the face of the Wikipedia editors if they re-insert this silliness.

(they also seem to be very attached to the many-species-of-architeuthis taxonomic view, but I have references documenting the controversy of that.)

Thanks

- M

 

[PurpleTentacle]

Wiki's been under fire from the Slashdot community recently (and probably several other communties) for their careless attitude toward user privacy and security. They had posted a list (that they have since removed) of users whose password hash values were identical to those of known trolls and problem users. Brilliant. They might as well have come right out and given their users' passwords to the bad guys. I'd change my wiki account password pretty soon if I were you.

 

[monty]

Wiki's been under fire from the Slashdot community recently (and probably several other communties) for their careless attitude toward user privacy and security. They had posted a list (that they have since removed) of users whose password hash values were identical to those of known trolls and problem users. Brilliant. They might as well have come right out and given their users' passwords to the bad guys. I'd change my wiki account password pretty soon if I were you.

Well, I checked that I wasn't on that list, but yeah, I guess. I doubt there are any nefarious people who care about my wiki password anyway, though, since I'm not much of a contributor and there's no useful personal or financial data associated with it. In fact, I did my first edit of the giant squid thing as an anonymous user, but I figured I'd make an account so I can actually post justifying my edits.

Thanks for the heads-up, though. Slashdot is sometimes a bit, er, polarized, of course-- they have a love/hate relationship with wikipedia, it seems. The whole wikipedia thing is sort of goofy, because there's not a formal system of fact checking, but it's pretty good for quick fact-checks as long as you keep in mind that it's only about 80% likely to be accurate.

 

[PurpleTentacle]

Slashdot is sometimes a bit, er, polarized, of course-- they have a love/hate relationship with wikipedia, it seems.

You can go even furhter and say they're a bunch of egomaniacs looking for a good flame war, but if they're concerned about something, it's usually something pretty scary.