To make a short story long...

I got my hair cut today, which is something I loathe even more than having my teeth cleaned. (While the results are wonderful in both cases, there's just something awfully disturbing about trying to sit still while sharp/pointy objects are being applied to bits of my head.) As I was waiting for my turn in the chair, I was trying to think of interesting things not to talk to the hairdresser about. (Where did all the barbers go?) While I was staring vacantly at a picture of some lovely model with some lovely haircut vacantly staring back at me, I hit upon chromatophores as a suitable topic to concentrate on while I was being tormented for the next 20 minutes. It was the model's makeup. It occurred to me that chromatophores would be an absolute godsend to most of the women I know. Think of the time, money, and frustration (mostly incurred by male companions) that could have been saved, if only the vagaries of evolutionary pressure had so allowed. (BTW, what's the deal with eyeshadow? :yuck: ) So here's what's been bothering me:

How did cephalopod chromatophores evolve? Are there any good theories or studies that indicate how this might have happened?

I'm having a hard time convincing myself of a plausible way around that "irreducible complexity" bunk.

I think I'll use this topic to bookmark some pages I find interesting. This is an article on ceph chromatophore systems by Andrew Packard:

Not for giant axons only (http://www.physoc.org/publications/pn/archive/article.asp?ARTICLE_ID=51)

This page links to the following, which has some kinda nifty little movies:

Andrew's Squid Experiments from a Physical Point of View (http://www.gfai.de/www_open/perspg/g_heinz/biomodel/squids/squids.htm)

Here's a story that almost makes me not regret majoring in applied math:

Mathematics reveals the cuttlefish's wink (http://www.newscientist.com/news/news.jsp?id=ns99993728)

Wish I had a bunch ('cuddle'? :) ) of S. officinalis to play with.


:rainbow:

Think of the time, money, and frustration (mostly incurred by male companions) that could have been saved, if only the vagaries of evolutionary pressure had so allowed. (BTW, what's the deal with eyeshadow? :yuck: )

I actually think it was a con job by the male of the species! If you look at most other species it's the MALE who gets all gussied up to attract a mate, somewhere along the line we got conned into putting that gunk on our skin for you fellas to admire(?)

BTW yes I DO have some eyeshadow & if you give me a year or so I may even remember where I put it...........don't wear it much (ever!) course that may be why I'm footloose & fancy free at the moment, that and the fact I have no life (the thesis thingy!) and often smell of eau d' squid! :lol: :lol: :lol:

J

I actually think it was a con job by the male of the species! If you look at most other species it's the MALE who gets all gussied up to attract a mate, somewhere along the line we got conned into putting that gunk on our skin for you fellas to admire(?)

Such is the price of enforcing monogamy (which I happen to prefer, since the alternative seems like too much damned work :D ). Shall I launch into my rant about De Beers? :x


Mmmmm, eau d'squid... :yuck:

Shall I launch into my rant about De Beers?
:x
If you like, personally, I prefer saphires!


J

Shall I launch into my rant about De Beers? :x
If you like, personally, I prefer saphires!

Shall I launch into my rant about saphires? :)

Shall I launch into my rant about saphires? :)

Sure, but I'll ignore you!!!!! :D :D (Anyhow I buy my own saphires! :( )

J

Shall I launch into my rant about De Beers? :x
If you like, personally, I prefer saphires!

All this talk of sparkly things reminds me of something...

I think my question should be expanded to encompass the evolution of cephalopod body patterning from a holistic point of view. (Does anyone even care? I'm going to turn this thread into a blog, eventually.) Doesn't the efficacy of chromatophores in crypsis/communication depend on the distribution of reflecting cells, iridophores, and leucophores? Does it make sense to inquire about the evolution of chromatophores in isolation?

I'm assuming that the whole papillation(?) issue can be studied separately from colouration. Does that make sense?

Enough questions. I'm going to :beer: :beer: :beer: ... :sleeping: now.

Avast! There be new smilies in the hold: :arr: I'll be raisin' a cup 'o me finest grog ta salute the beauties (sorry, Phil) that painted these! Arrrrr!

BTW; thanks, Jean, for being the only person to reply to this thread. As for you hundred (or so) others...

:P

Well I think these are good questions... in fact I promoted them in the newsletter last week!

Tough ones though... evolution of chromatophores... Have you seen this one?

Shells are often seen as a major contribution to the success of molluscs. Why, then, have many molluscs lost or reduced their shells? (http://www.andrewgray.com/essays/molluscs.htm)

Talks about how the shedding of shells led to the evolution of chromatophores.

That's from Andrew Gray, not to be confused with Andrew Packard from one of your excellent links up there...

Does it make sense to inquire about the evolution of chromatophores in isolation?

I would think so!

Great link, Tony! That subject could use its own thread...

Loss of the shell, not to mention coevolution with fish, is clearly going to be important in the evolution of body patterning. So we're looking at something like 350 million years (Phil?) of evolution, which is a heck of a lot of generations for animals with such short lifespans. Plenty of opportunity for all sorts of crazy adaptations. Hmmm....

What I've been looking for, most recently, is some kind of investigation into how chromatophores develop in embryonic cephalopods (feeling out the "Evo-devo" angle). Such information is proving very hard for me to find. Any marine biologists out there care to suggest a better method of searching than Google?


:confused:

Interesting the comment that deep sea cephs could get there because they had no shell, Packard (1972) went with the opposite, because the cephs went deep they lost their shells due to increased hydrostatic pressure and then some of the shell-less beasties recolonised the shallow water! I think this is one of those chicken & egg questions! Another one is did the chromatophores develop before the good eyesight or did the eyesight develop because the cephs needed to be able to see the patterns in their school mates :bugout: It's interesting that Nautilus with relatively poor eyesight has no chromatophores!

J


Reference: Packard, A. 1972 Cephalopods and fish: The limits of convergence Biological Reviews vol 47, p. 241-307

.... well, they haven't exactly 'lost' their shell, it's just been internalised in most cephs.

Cirrate (finned) octopods still retain a shell (internalised, variably U-, V-, W- or saddle-shaped); Vampyroteuthis has that bizarre shield-shaped vestige; squid still retain the gladius in most (although things like Sepioloidea completely lack a gladius/pen/shell); many benthic octopodids (Octopus and kin) still retain a shell vestige, in the form of dorsal stylets embedded in musculature inside the mantle, in some the stylets are calcareous; Spirula still has a calcareous shell .... and of course there's Nautilus. In non-nautiloids, as a rule the shell has been reduced and internalised, with secondary development in the likes of Argonauta.

... but evolution of chromatophores ..... hmmmm.

Interesting the comment that deep sea cephs could get there because they had no shell, Packard (1972) went with the opposite, because the cephs went deep they lost their shells due to increased hydrostatic pressure and then some of the shell-less beasties recolonised the shallow water! I think this is one of those chicken & egg questions!

I'm sure I don't really know what I'm talking about, but Packard's scenario seems less likely to me. Perhaps I'll change my mind when I actually read what he has to say.

Another one is did the chromatophores develop before the good eyesight or did the eyesight develop because the cephs needed to be able to see the patterns in their school mates :bugout: It's interesting that Nautilus with relatively poor eyesight has no chromatophores!

Interesting. Narrow-minded fella that I am, I had assumed body patterning evolved primarily for the purpose of crypsis, with communication being an exaptive(?) development. Now I'm thinking that it might make a lot more sense if it were the other way 'round. It seems to me that crypsis would require a much more complete system to be effective, whereas even primitive stages in the evolution of body patterning could be useful for display/communication.

I was wondering if there are any known cephalopods with chromatophores that emit light frequencies outside the visual spectrum. It may be fanciful, but the notion of deep sea cephalopods using short wavelength light emitted from chromatophores as a type of active or passive lidar is appealing to me. I suppose the biggest problem would be the difficulties light has in traveling through water, but if a cephalopod's eyes were adapted to compensate for the diffusion and refraction of deep water, it would make for a very effective detection system. I guess I'm supposing that some cephalopods could evolve (or could have evolved) to use their eyes and chromatophores the way bats use their ears and echolocating sonar. Nature has come up with stranger ideas!

I know this isn't really about how chromatophores evolved, but the 'why' of evolution often answers the question of 'how'. :)

Evolution of chromatophores? Well, I’ve had a bit of a think about this and I think that these were a development of the earliest coleoids. I’ll tell why I think this is, but please feel free to shoot me down in flames if you wish! Fossil coleoids, excluding belemnoids, are very rare due, of course, to their soft bodied nature. There do not appear to be many researchers working on them at present and doubtless with one or two future discoveries the whole working system will have to be reworked. Anyway…….

I think the key to this lies with Vampyroteuthis. The Vampire squid is the only surviving member of the Vampyromorpha that we know of. The Vampyromorpha were an incredibly ancient lineage, recent cladistic analyses such as the one available here (http://userpage.fu-berlin.de/~palaeont/fossilcoleoidea/phylogenetictree.html) indicates that the Vampyromorphs were at the root of one of the two main branches of the coleoids, the other being the belemnoid families which split from a common ancestor probably in the early Carboniferous sometime around 350mya. Most of the fossil ‘squid’ that one sees depicted from deposits such as the later Jurassic Solnhofen were members of the Vampyromorphs.

It is believed that these Vampyromorphs and the lineage that led to the modern squid, and cuttlefish, split from a branch soon after this initial divide from the ancestral coleoid, with the modern Spirula representing a comparatively unmodified ancestral form. It is believed that this split into the modern squid and cuttlefish probably happened in the early Tertiary, following the massive Cretaceous marine extinctions. The octopus lineage is thought to have split sometime in the Jurassic from the Vampyromorpha, the earliest known example being Proteroctopus ribeti (160mya)

What has this to do with chromatophores? Well, according to cladistic analyses Vampyroteuthis, the modern squid, cuttlefish and octopus all appear to have had a common ancestor that lived in the early Carboniferous and all these groups have modern examples that demonstrate chromatophores. Unless it is conceivable that chromatophores evolved independently in all these groups, which seems unlikely, it seems at least a strong possibility that the common ancestor of all these groups would have possessed chromatophores at a date of around 350mya. This ancestor had only comparatively recently split from the initial branch in the coleoids in the late Devonian. Perhaps one could speculate that possibly the belemnoids would have possessed chromatophores too, if the common ancestor of both groups had possessed them. (Practically impossible to prove though!).

Vampyroteuthis does have chromatophores though they have weak musculature. To quote from the Tree of Life pages:

“These chromatophores, however, have lost the muscles that enable rapid color change in other coleoids and are probably incapable of changing shape. A few normal chromatophores associated with photophores are still present.”

This is probably an adaption to life in the abyss; who needs a colourful display in the dark? Early Vampyromorphs were certainly not all deep water animals. The recent discovery of an Upper Cretaceous animal from Japan that has been named Provampyroteuthis giganteus is believed to have swum in the surface waters and was much bigger than the modern Vampyroteuthis. Living in an off–estuary environment it is quite possible that this animal had developed chromatophores to a higher degree than its modern descendant. Fossils of this animal have been recovered from stomach contents of Elasmosaurid plesiosaurs; these were believed to be surface or shallow water swimmers. (I can print the reference for this if anyone wants to follow it up).

I’m sure that I have managed to make something comparatively simple much too complicated. This stuff is so much easier with a diagram and timeline, you know!

:vampyro: :bonk:

I was wondering if there are any known cephalopods with chromatophores that emit light frequencies outside the visual spectrum.

While I'm not able to answer that question, I do know of a few species of fish (e.g. Pachystomias microdon) that use red light from photophores under their eyes as a kind of searchlight to locate prey. Many of the animals in the deep sea, as far as I know, cannot see red light since virtually none penetrates to any significant depth. Is this the sort of thing you had in mind?

I know this isn't really about how chromatophores evolved, but the 'why' of evolution often answers the question of 'how'.

That's sort of how I look at it. The 'how' of it is a series of steps, and each step answers a 'why'. I hope this thread touches upon various aspects of ceph body patterning and photophore use, not just the evolution of chromatophores. I don't think that question can really be answered, but hopefully it'll lead to other interesting questions and observations (like yours).

(I can print the reference for this if anyone wants to follow it up).

Please do!

I was hoping you'd weigh in with something like this. :D

Must digest...

Here you go!

Kanie, Y., Hasegawa, Yoshikazu, Okazaki, Y. and Tatematsu, Yoshiko; 1998:

Vampyromorphs: past and present; - Cretaceous vampyromorph (Coloidea: Cephalopoda) as the diet of a plesiosaur; Bulleton of Gunma Museum of Natural History (Number 2) pp: 11-23

If anyone tracks this down , please let me know! Providing it's not all in Japanese, of course. :D

I have just discovered a wonderful article:

Messenger JB (2001) Cephalopod chromatophores: neurobiology and natural history. Bio Rev 76: 473-528

I have yet to actually read any of it, but it appears to be fairly comprehensive (for its length).

5 pages of references. Hooray! More bloodshot eyes!

I just realized that yesterday was my one-month tonmoversary. I'm going to use this as an excuse to have a little extra :beer:, and I invite everyone to do the same (provided you have achieved the relevant legal drinking age).

You know you want to.


(and remember: JD and Coke might be a good mix, but drinking and driving aren't!)

I just realized that yesterday was my one-month tonmoversary.

Happy Tonmoversary um...... It's been great to have you online
Cheers
O

I just realized that yesterday was my one-month tonmoversary.

Happy Tonmoversary um...... It's been great to have you online
Cheers
O

Thank-you, sir. It's certainly great to be here, interacting with like-minded individuals for a change.

tonmo.com is my happy place.

Here's a pdf of the chromatophore article by Messenger:

Cephalopod Chromatophores: neurobiology and natural history (http://www.cephbase.utmb.edu/refdb/pdf/6818.pdf)

I love CephBase (http://www.cephbase.utmb.edu).

Still reading...

:madsci:

Thanks! Now I know what I'm reading tonight, when I should be writing :(

Melissa

The section on pharmacology scares me.

Messenger (2001) (http://www.cephbase.utmb.edu/refdb/pdf/6818.pdf) seems inclined to think that "the chromatophores may have evolved primarily for concealment" from "sharp-toothed predators", which became necessary as the external shell was lost. How effective was the shell at keeping predators from eating the occupants? In Ammonites ( :thumbsup: :thumbsup: ), Monks and Palmer write:

Ultimately, cephalopods have had to trade-off increased mobility and swimming efficiency against the defensive properties of the shell. The shell can be thought of as being under a constant 'crushing attack' from the surrounding water. The thinness of the shell and the lack of structural support between each septum, mean the shell has little extra strength to resist the additional forces from a predator's bite.

The shell is obviously going to provide some measure of protection, but more sturdiness will eventually come at the expense of buoyancy. Looking at an ammonite shell, I get the impression that buoyancy is a pretty big deal.

Andrew Gray, in Shell loss in mollusc evolution (http://www.andrewgray.com/essays/molluscs.htm), suggests that:

The internalisation of the shell provides coleoids with several advantages, most of which are related to the development of more efficient swimming. (The coleoids may originally have evolved in response to increasing competition from predatory fish, with which they are convergent in many ways.) Liberation from an external shell helps the coleoids to float horizontally in the water, and has allowed the development of fins for better locomotion, and a highly contractible mantle cavity that can squirt out water violently, moving the animal by jet propulsion.

Basically, I'm getting back to my Jean-inspired epiphany of several posts ago: Might the early development of body patterning have been driven by its use in communication at least as much as by its use in concealment?

If the shell is overrated as a defensive adaptation, and coleoids end up being more mobile (and presumably harder to catch) without large external shells, how badly would crypsis be needed? I'm also making the big assumption here that a chromatophore system in the very early stages of development would not be anywhere near as effective as the finished product, and might even be occasionally harmful.

Anyone care to set me straight?

:bonk:

Hmm…

OK, here’s a bit of a half-baked argument against what I just said.

Consider the case of a young early coleoid, possibly living a life something like a young cuttlefish’s (i.e., benthic). This guy is bite-sized and can’t do as much running or fighting as his larger conspecifics. He is in much greater need of camouflage, since hiding is going to be his shtick. Perhaps early chromatophore systems produced less structured patterns that were more along the lines of Disruptive, and were in fact sufficient to provide some degree of protection for this little guy when hiding over a mottled rocky bottom or partially burying himself into sand. Breaking up his outline might be a good start, even if he can't blend into the background as well as a modern octopus could.

That still leaves me with a million questions…

:confused: , and still :bonk:

Man, I spend way too much time talking to myself.

um...

You aren't talking to yourself, we're just still thinking it through and reading to catch up enough to offer a reply. I should have one around November 14 at the earliest!

Melissa

um...

You aren't talking to yourself, we're just still thinking it through and reading to catch up enough to offer a reply. I should have one around November 14 at the earliest!

Melissa

I didn't mean to imply that I felt alone here, just that I tend to argue with myself too much. I was suggesting to myself that maybe I should shut up a little, and stop replying to my own posts. Other people tend to have more interesting things to say.

:bonk:

Here's an intriguing thought: we know that many cephalopods are pretty bright (for molluscs), and seem to have very highly developed sensory systems (most notably the eyes). What if the advanced chromatophores of many species are not the result of ongoing evolution, but a remnant from a time when cephalopods were much more intelligent? Imagine a species of now-extinct cephalopods with the capacity for advanced communication, moreso than dolphins or other cetaceans, using light instead of sound. We know that dosidicus (for one) hunts in packs; could this be an instinctual remnant of more advanced cooperative thinking? This is purely speculative, but it is certainly worth investigating.

Here’s a thought. As chromatophores are used for visual display, then it follows that they must have evolved in tandem with eyes capable of observing that display. The nautiloids almost certainly had very poor eyesight; think of the modern Nautilus with its pinhole camera type eye. I think it is unlikely that these animals would have evolved these organs. Besides, chromatophores are not present in the modern Nautilus, which uses its striped shell as camouflage.

There is no evidence of eyes in the ammonites; not that they were not present, but we have no soft bodied ammonite fossils to be used as evidence. The ammonites are a bit of a red herring here anyway, as they split from the common ancestor with the coleoids somewhere in the mid to late Devonian, roughly about 370million years ago and are only very distantly related to modern squid. This common ancestor, the Bactritida itself had probably split from the nautiloids somewhere around 400 million, only a few million years before.

The belemnoids and the vampyromorphs, (from which the squid and octopus recently evolved) both of which were probably highly visual animals, themselves divulged from the bactritids in the early Carboniferous, only a few million years later. This could imply that the evolution of complex eyes systems and consequently chromatophores must have happened in a short space of time, probably in the mid Devonian-E. Carboniferous. This is when the earliest common ancestor of all the coleoids lived. Unless all the modern coleoid groups evolved chromatophores independently, they must have been established at this early date.

The upshot of all this is that it seems to me key lies with the obscure bactritids, which was a linking group between the nautiloids, coleoids and the ammonoids. They existed in the short window of time in the Devonian between the externally shelled nautiloids, with no chromatophores and poor eyesight, and the appearance of the internally shelled coleoids with chromatophores and good eyesight.

Perhaps I’m making too many assumptions here, and apologies this was a bit repetitive of my post above. Please forgive, I’m still trying to think this through…..

Um,

Great thread you've started. My head hurts, but in a good way.

The presence of chromatophores on the viscera of some cephalopods has got me to wondering where on the early cephalopods chromatophores first began to appear: on the dermis, or in the guts? Did they take hold first for their value in obscuring the appearance of internal organs (and the contents of the gastric tract) visible through the transparent/translucent bodies of larval cephalopods, or did they "migrate" internally to mitigate the loss of an opaque calcareous shell's light-blocking qualities?

:?:

Clem

What if the advanced chromatophores of many species are not the result of ongoing evolution, but a remnant from a time when cephalopods were much more intelligent? Imagine a species of now-extinct cephalopods with the capacity for advanced communication...

What if they're still out there? Why not?

People around here are pretty good at making feel dumb (see any post in this thread). :)

The presence of chromatophores on the viscera of some cephalopods has got me to wondering where on the early cephalopods chromatophores first began to appear: on the dermis, or in the guts? Did they take hold first for their value in obscuring the appearance of internal organs (and the contents of the gastric tract) visible through the transparent/translucent bodies of larval cephalopods, or did they "migrate" internally to mitigate the loss of an opaque calcareous shell's light-blocking qualities?

I never even thought about the need for chromatophores in larval cephalopods. It's funny how I keep forgetting that 'natural selection' applies to all stages of the life cycle. (I think this might be due to the fact that most of my initial learning about evolution was picked up while studying genetic algorithms. I’ve been reading about ontogeny recently, though, so that’s a pretty weak excuse.)

As for whether chromatophores first appeared on the dermis or in the guts, the only evidence I can think of is the fact that older (black-brown) chromatophores lie closer to the epidermis than younger (orange-yellow) chromatophores. Yeah, I know that’s pretty weak.

You make an excellent point regarding the need to hide the guts. These little guys might be quite likely to eat some bioluminescent plankton, which is no good for hiding in the dark if their innards are mostly transparent. At the same time, being transparent is pretty handy during the day (especially for pelagics). So, what would be ideal is to be pretty much transparent during the day but more opaque at night. Simple pigment cells are only going to help with the latter, but even the crappy hormone-regulated type of chromatophore might provide a workable all-around solution. (How did that kind evolve, by the way? :twisted: )

Any thoughts on what the precursor to the chromatophore organ might have been? Anyone?

The upshot of all this is that it seems to me key lies with the obscure bactritids, which was a linking group between the nautiloids, coleoids and the ammonoids. They existed in the short window of time in the Devonian between the externally shelled nautiloids, with no chromatophores and poor eyesight, and the appearance of the internally shelled coleoids with chromatophores and good eyesight.

Perhaps I’m making too many assumptions here, and apologies this was a bit repetitive of my post above.

Far from being repetitive, this complements your post above by attacking the question of timing from the early end. We mustn’t forget about the bactritids. You make a pretty strong case, based on the available evidence (I’ll have some questions for you about the available evidence, later). It’s also good to be reminded where ammonites don’t fit in.

I’m inclined to believe that chromatophores would have evolved after some kind of reflecting cells. Anybody feel like tackling the question of leucophore/iridophore evolution?

:read:

[this post has been edited]

For Clem:

Clem, when you mentioned light-blocking, what light did you have in mind? Were you thinking along the lines of bioluminescence caused by prey, light produced by photophores (presumably used for counterillumination), or something else?


For all:

From Messenger (2001) (http://www.cephbase.utmb.edu/refdb/pdf/6818.pdf):

We should also make clear that cephalopod chromatophores are always assumed to lack a direct response to light (the so-called 'primary' response, common in many invertebrates, Weber, 1983). However, Packard & Brancato (1993) claim that, in Octopus vulgaris and O. macropus, light may act directly on the skin and this obviously merits further investigation.

I certainly agree. It would be quite nice to know whether or not such an effect existed, and what mechanisms might be involved in such a response. I'm attempting to track down the article referred to:

Packard, A. & Brancato, D. (1993). Some responses of Octopus chromatophores to light. Journal of Physiology, London 459, 429P.

I don't suppose anyone knows any more about this, eh?


I know a lot of people might have already seen this clip of Octopus vulgaris (http://www.cephbase.utmb.edu/viddb/vidsrch3.cfm?ID=132&CephID=495) from CephBase (http://www.cephbase.utmb.edu/), but I found it so amazing that I was compelled to post a link to it (I recommend the mpeg over the avi).

Gotta do some work now, will babble more later...

For Clem:

Clem, when you mentioned light-blocking, what light did you have in mind? Were you thinking along the lines of bioluminescence caused by prey, light produced by photophores (presumably used for countershading), or something else?

Um,

I was thinking mostly about luminescent prey items: animals that generate their own light (primary) and animals that consume bioluminescent organisms which might remain active light-producers for a short time after consumption (secondary). Bio-luminescence that persisted after maceration, radular grinding and transit through the esophagus into the GI tract would seem to require either an active (chromatophores on the gut) or passive (dark pigment on the mantle wall) counter-illumination strategy on the part of the cephalopod in order to maintain low visibility. Larval and juvenile cephs with transparent/translucent bodies that ingest small luminescent organisms would be at high risk, unless they restricted their pursuit of food to the daylight hours, and kept close to the surface. I might be totally wrong about this, but I'd expect that cephs with internal, light-blocking chromatophores would have a decisive evolutionary advantage, by being able to feed at all hours and with diet restricted only by availability of manageably sized prey.

On a tangent (sorry!), I noted a reference in Messenger ("Cephalopod Chromatophores: Neurobiology and Natural History," p. 5) to cephs whose external chromatophores retracted completely upon "exposure of cephalopod skin to ammonia fumes." Do the ammoniacal squids have to do something differently, then?

Um, thanks for posting the PDF link for the Messenger text. Great stuff, and I've lots to learn.

:bugout:

Clem

I was thinking mostly about luminescent prey items

I'm glad my assumption was correct. I was going to bring up the photophore issue, but then decided that it might be better to leave those worms in the can for now.

On a tangent (sorry!), I noted a reference in Messenger ("Cephalopod Chromatophores: Neurobiology and Natural History," p. 5) to cephs whose external chromatophores retracted completely upon "exposure of cephalopod skin to ammonia fumes." Do the ammoniacal squids have to do something differently, then?

I'd like someone to explain to me exactly how ammonia acts to produce that effect. I am almost completely ignorant concerning matters of physiology.

Ammonia is generally quite toxic, is it not? It reacts with water in a rather exothermic reaction which produces highly alkaline ammonium hydroxide (burns, burns, burns). I was under the impression that ammoniacal squid actually use an ammonium chloride solution for buoyancy, and that the ammonium (NH4+) cation is much less toxic than ammonia (NH3). However, there is a very good chance that I don't know what the **** I'm talking about. I would appreciate some enlightenment on this issue.

I was under the impression that ammoniacal squid actually use an ammonium chloride solution for buoyancy, and that the ammonium (NH4+) cation is much less toxic than ammonia (NH3). However, there is a very good chance that I don't know what the **** I'm talking about. I would appreciate some enlightenment on this issue.
Um,

Trust me, I don't know what the **** I'm talking about. Can you say "rank amateur?" It's spelled C-L-E-M. (I need to finish reading the Messenger text.) This is a good place to ask clumsy questions, though.

As for the photophore can of worms...I'm not touching that with a 10-foot flying gaff.

:roll:

Clem

Can you say "rank amateur?" It's spelled C-L-E-M.

Humility is nice, Clem, but saying you're a "rank amateur" is a bit disheartening to those of us who are beneath you. :)

There's a photo of a translucent juvenile octopus (Octopus sp. is all we get for an id) on page 259 in Cephalopods: A World Guide that convinces me (even more) that you might be on to something with the visceral chromatophores. I wish I had a scanner here.

As for the photophore can of worms...I'm not touching that with a 10-foot flying gaff.

C'mon, it'll be fun! TTF already gave us a start in her Deep-Sea Cephalopods (http://www.tonmo.com/science/public/deepseacephs.php) article.

:idea: :rainbow: