Not sure if it belongs on this forum, but I think this recent ScienCentral news release is pretty interesting:

http://www.sciencentral.com/articles/view.php3?article_id=218393097

Interesting.........although I think squid musculature is rather tougher than jello!!!!

J

I'm sure I've asked this before, but of what material are cephalopod beaks composed? I'm guessing keratin, or something similar, but is any metal used? (Thinking of the radulla of certain marine snails here)

I think they are chitinous.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1559839

CG is right Chitin is the stuff!

Very nice. Very lightweight, yet strong.

thats interesting. i wouldve thought there would've been calcium in squid beaks. thats different.

Actually calcium has some issues as to fixing under high pressure, so chitin or a protein works better

so, obviously cuttlebones (presumably including spirula) and nautilus shells are calcium based... are squid pens and the vestigial shells of some octos also rather than chitin? How about statoliths? I know squid sucker rings are also chitinous. How about radulas? and yeah, I could probably look this stuff up if I wasn't lazy... Is it pretty much across-the-board that all cephs can make both calcium and chitin based hard bits?

weird. i wouldve figured otherwise

gladii (pens) are chitinous also, as is the radula. Statoliths are calcareous.


J

gladii (pens) are chitinous also, as is the radula. Statoliths are calcareous.


J

So I guess that implies that somehow the system that builds the gladius, which seems pretty likely to be homologous to the cuttlebone and shell, somehow changed, within the decabranchia, to be chitinous (and non-chambered) somehow... I wonder if that involved a regulatory switch in the gene battery used to make it all at once, or if there was a chitinous component to the calcite that remained when the calcite was lost, or what. And now I really want to know what the vestigial shells in octopus are made of, since they clearly diverged earlier than squids and cuttles (and I need to check if vampyroteuthis has some homologous internal structure.) I'll mention the (probably) red herring to avoid that the argonaut shell is not believed to be homologous to the structures we're talking about, although that then raises a lot of questions about why its shape is so similar to ammonite shells.

off to tolweb and google...
I'm back, did you miss me?

results: vampyroteuthis has a chitinous gladius, spirula is calcareous as expected, cirrata have a shell with "cartilage-like structure" and incirrata have "stylets" including Haliphron atlanticus with a "gelatinous" shell (not clear what it's made of) and some other octopodidae have "stylets" which are described both as cartilaginous and "often mineralized."

wow. i am now way out of my league. i just had to google like every other word in that statement.

wow. i am now way out of my league. i just had to google like every other word in that statement.

I hope I didn't misspell too many of them...

Actually, I didn't use the word that probably sums up a lot of my thinking: polyphyly (http://en.wikipedia.org/wiki/Polyphyly), or, more specifically, my curiosity that chitonous shell/gladius/pen/cuttlebone/stylet material might be polyphyletic, in that it occurs in both the decabranchians like squids, but also the octopods like octopus and vampyroteuthis, which would mean that the last common ancestor had a calcium-based shell material which was lost somehow in both squids and octopuses, but not in some of their shared ancestors. When this happens, it's interesting because it either means that the ancestor had a predisposition to this trait, so it was easy to happen in two separate lineages, or that there is an immense selection pressure for it (which seems unlikely here). I suspect that belemnites had both a calcareous phragmacone shell part, and a chitinous pen analog, and that could be the commonality, since vampyroteuthis having a chitin squid-like pen pretty much proves that it's there fully formed in both lineages, unless there's a major mistake in the accepted phylogeny (evolutionary tree) of coleoid cephs... that possibility is what makes polyphyletic traits very interesting to biologists, in the sense that science makes the most progress not in "just as a thought" moments but rather "that's funny, I didn't see that coming" observations.

So I guess that implies that somehow the system that builds the gladius, which seems pretty likely to be homologous to the cuttlebone and shell, somehow changed, within the decabranchia, to be chitinous (and non-chambered) somehow...

Hmm... The gladius has ridges in it, which might be growth lines. I need to do some more reading before replying on analogies to cuttlebones...

Hmm... The gladius has ridges in it, which might be growth lines. I need to do some more reading before replying on analogies to cuttlebones...

weeelllllll they're not as defined as an actual ridge (at least not in N. sloanii :roll:) See attached piccy in the word doc!

not sure how they originate however I know that the increments in bivalve shells are calcium (and/ or aragonite) in a protein matrix, so perhaps the calcium has been lost and the protein matrix remains.

J

well monty, that made a hell of a lot more sense.

How's this, then:

Squids have a pen made of chitin, like crab shells. Cuttlefish have, in the same place, a cuttlebone made of some calcium stuff like a seashell... but some octopuses and their relatives have something like the pen also made of chitin. This is weird, because squids and cuttles are supposed to be more closely related to each other than they are to octopuses, but it's pretty much believed that their last common ancestor had a calcified internal shell like the cuttlefish. Did the squids and octopuses lose their shells in the same way? What would this tell us about how they're related or what the last common ancestor was like, since squid- and octopus-like animals haven't left much of a fossil record?

I'm not trying to be too jargon-heavy, it's just sometimes easier to express things the way they're discussed in papers, and anyway, I need some practice with some of this stuff. On the other hand, if you can't explain something without jargon, it's usually a sign that you don't understand it, so writing the version in this post is probably character-building for me as well.

oh no that wasnt sarcasm. my bad

oh no that wasnt sarcasm. my bad

oops, my bad, too, I guess... but it did get me to wake up and think about how much I was using two dollar words where it wasn't really that important to my point. It's an interesting exercise to put the "use the vocabulary in a context where people can learn it" version next to the "how can this be explained so that it makes sense directly" version.

Like I said in another recent post, one of the things I like about TONMO is that there's a range from professional researchers to grade school students, so it's worthwhile trying to make sure we cover all the bases... of course, we'll probably always have both academic discussions and enthusiastic novice questions, and shouldn't have every discussion cover both, but this got me thinking about looking for opportunities to cover a wider range...

yea. thats the best part of tonmo. super collective ceph knowledge. its awesome. i probably wouldve had at least one dead octo by now if i hadn't been recommended to this site. to be honest, i was completely clueless. i had no idea about the 3 month cycling to make sure your tank is mature, the set up of a tank, their unusually high waste production, i didnt know a thing.

weeelllllll they're not as defined as an actual ridge (at least not in N. sloanii :roll:) See attached piccy in the word doc!

not sure how they originate however I know that the increments in bivalve shells are calcium (and/ or aragonite) in a protein matrix, so perhaps the calcium has been lost and the protein matrix remains.

J

Yeah, increments is a better term, in my sleep-deprived state I couldn't come up with a better word than "ridges"... That's why I didn't continue with my post about cuttlebones, I wanted to be sure I was correct before I posted something...

so, obviously cuttlebones (presumably including spirula) and nautilus shells are calcium based... are squid pens and the vestigial shells of some octos also rather than chitin? How about statoliths? I know squid sucker rings are also chitinous. How about radulas? and yeah, I could probably look this stuff up if I wasn't lazy... Is it pretty much across-the-board that all cephs can make both calcium and chitin based hard bits?

There's a lot of Gastropods and Polyplacophorans who have metal in their radulas. That is SO beyond cool.

There's a lot of Gastropods and Polyplacophorans who have metal in their radulas. That is SO beyond cool.

VERY cool, so much fun to tell a group (kids OR adults) about it, listen to them all tell you you're a fibber then whip out a preserved radula and a magnet (metal is magnetite you see!) fun fun fun :twisted:

J

I would be in awe at that demonstration! Where does the metal COME from to be incorporoated? It can't be animal produced so it must be eaten/collected from something.

I would be in awe at that demonstration! Where does the metal COME from to be incorporoated? It can't be animal produced so it must be eaten/collected from something.

magnetite is a form of iron which is in seawater, so they must incorporate it from the seawater, but I don't really know the mechanism and I've not been able to find a satisfactory explanation anywhere!

J