Sucker Ring Composition

Graeme said:
Chitin, I think. Only calcareous part in a ceph is the internal shell of cuttles, as far as I'm aware...

Graeme

Er, I think you're forgetting nautilus in that blanket statement. I've read somewhere that the argonaut shell was evolved independently rather than being related to the shell that was lost in the coleoids, but I'm not sure how they know that or what it's made of. Given its shape, it seems likely that it inherits some from the archaic shell formations of the original ceph ancestry.

Particularly given the the Honolulu aquarium is one of the few places to be able to raise nautilus from eggs, it's be really nifty if Martindale et. al. did the same sort of HOX control analysis for nautilus that they did for the Euprymna, and we could see how the HOX controls the layout for the shell and the non-decapod arrangement...

(see http://www.nature.com/nature/journa...l;jsessionid=4FD50828DF36DE4CD9D3F63D7FFA444E and http://pharyngula.org/comments/558_0_1_0_C/ )
 
Landman et. al., 2006, Jaws of late Cretaceous placenticeratid ammonites : how preservation affects the interpretation of morphology. American Museum novitates ; no. 3500

They are preserved as steinkerns with a thin film of black material, representing diagenetically altered chitin. X-ray diffraction analysis of samples of this material indicates that it consists of magnesium-rich c...

didnt read it all but the rest of the abstract (after the ...) reads: calcite, pyrite, and amorphous material (organic compounds).
 
was just looking into argonaut shell info on tolweb and saw this interesting factoid at Haliphron atlanticus

Unlike other members of the argonautoid families, Haliphron has a remnant of the true shell - a short, thick almost gelatinous stylet (Voight, 1995). H. atlanticus, like other members of the argonautoid families except species of Argonauta, has a hydrostatic organ (Bizikov, 2004).

if it really is a vestigial shell, I'd expect it to be calacareous as well, but it doesn't say. That's the first I've heard of this-- does anyone know what its shape is like? That's the only internal shell I've ever heard of in an octopod... it seems like it'd say a lot about what the early coleoid octo-ancestors looked like...

TOL also says:
Argonauts are muscular, pelagic octopods. Females secrete a thin calcareous "shell" in which they reside

and

Presence of external shell in females secreted by the dorsal arms.

so I guess argonauts' shells are indeed calcium-based as well. The "secreted by the dorsal arms" seems like another good candidated for comparing the HOX control of argonaut shell excretion to nautilus!
 
Ok, I have another question: How are the rings created? What secretes the chitin?

Actually I have another question: Are ceph's born with the full quota of suckers, only they're much smaller, or do they acquire more as the arm grows?

Graeme
 
Graeme said:
Ok, I have another question: How are the rings created? What secretes the chitin?

Actually I have another question: Are ceph's born with the full quota of suckers, only they're much smaller, or do they acquire more as the arm grows?

Graeme

They definitely 'grow' them as the arms increase in length. How the rings are created .... well, that's another thesis .... and would involve a tremendous amount of histology (and comparative anatomy). What a tremendous subject for research that would be!
 
Steve, would Auckland uni ever consider offering a place for a PHd on sucker rings, be it composition, development or what I'm looking at: comparative morphology?
.... just out of curiosity...

Graeme- only scraping the surface, but at least its a start
 
My mind is ticking over as to how it would be done. I could not offer a stipend (as in living allowance scholarship), but could offer a full-fees scholarship (the cost of your enrolment would be zero $); you'd just have to accommodate & feed yourself.

One problem that I see with a programme like this is the histology, especially because you'll be sectioning through a hard structure that will want to destroy the soft part prep when the blade goes through. You'd want to replace the sucker ring with something that is softer - through some fan-dangled technique that I don't know about, but I am sure is common practice elsewhere (with bone).

You'd need ontogenetic series of identified species in pretty much all families of squid and octopus (otherwise you'd go insane if you had to identify them yourself).

You'd want to look at the composition of the sucker rings and hooks - and we've got all the toys here to do that (just don't ask me how to operate them or interpret the data; we have other people that can do that).

It would be very interesting!!
 
one other problem is that I know nothing about histology (or if I do, I'd have to try and locate it in the dark recesses of my brain! Not an entirely sanity-safe thing to do!:lol: ). You are getting me interested though! What I'll try to do just now is find out more about doing PHd's. I wanna try and get everything coursewise done first before I can relax and think about the future (time aint a luxury for me at the moment:cry:). Although like I said, I am interested in finding out a wee bit more!

I think it would be interesting too, if slightly sanity-draining.:wink: :razz:

Graeme
 

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