The ammonium vacuoles would make sense as a buoyancy adaptation, although its eerily looking more and more fishlike. What's next, swim bladders? Gee...
Why wouldn't they just retain the ions in their flesh? And is this the case across the entire Pholido- and Lepidoteuthidae families?
Heh heh... These body plans just get weirder and weirder. If in the future I'm sitting on a tropical beach somewhere, and some scaled octo comes out of the surf, slides up to me to ask me for some raspberry sake, I'm quitting!
There is an octopus with a 'swim bladder' - a very bizarre arrangement. It is found in the female of Ocythoe tuberculata, but I'm not sure if the male also possesses this structure (the female is considerably larger than the male); family Ocythoidae, monotypic.
I've only ever dissected one mature female (they're quite scarce); they also brood embryos in their distal oviducts - another very bizarre attribute for a cephalopod.
I agree with you John that they might as well distribute ammonium ions throughout the body tissues if achieving buoyancy was the sole purpose of these scale-like structures in the Lepidoteuthidae and Pholidoteuthidae. Lepidoteuthid squid are way-cool (and very rare, at least in collections) squid!!!
There is an octopus with a 'swim bladder' - a very bizarre arrangement. It is found in the female of Ocythoe tuberculata, but I'm not sure if the male also possesses this structure (the female is considerably larger than the male);
It does appear, from this site, that this structure is only present in the females. This species displays extreme sexual dimorphism with the male at about 30mm being about a tenth the length of the female. It also mentions that Ocythoidae are the only octopus family that bear live young, with the juveniles hatching in the oviducts. Is this truely a unique approach amongst the cephalopods, or are there others?
The male has also been known to hide inside the bodies of salps (free swimming sea squirts), leaving the protection when approached and retreating when the threat has passed! (Source here: Mark Norman's Cephalopods: a World Guide).
It really is quite astounding the sheer diversity of body plans and differing functional mechanisms within the cephalopods. So many different approaches to the same problems, and so many resolutions.
See, I think that there is a possibility, however remote, that ancestral traits "lost" along the evolutionary path are still encoded in DNA. albeit sleeping between relatively recent STOP and START codons.
Hope you don't mind me risking sidetracking this interesting discussion about Lepidoteuthis, but I once saw a fascinating TV documentary that demonstrated your point, John. I am not exactly sure how it was done but a certain section of DNA coding was chemically 'switched off' somehow in an embryonic chick. The section that was turned off controlled the formation of the beak. When the chick was X-rayed a few days later it seems that instead of a beak fully forming, rudimentary teeth began to develop along the jaw. The idea here was to demonstrate the dinosaur/bird link and that 'fallback' structures are indeed encoded in DNA. Atavism indeed!
I freely admit I do not understand genetics in any detail. Would the sequence of genes that caused the teeth to form been a recessive trait?
You might like to look this up, the experiment was three or four years ago. Anyway, back to the squid........
Wouldn't it be so nice to be able to grow these squid from the eggs, then subject them to all manner of environmental or genetic perturbations ....
I know I run the risk of further hate mail by making suggestions like these, but if you can manipulate chick embryonic development to the extent these ancestral characters/states appear, then just imagine what you could do with ..... Spirula for instance. Would an ammonite develop? Or what would become of Vampyroteuthis? Cirrates also .... what ancestral characters/states would appear????
These are exciting, but at the same time ethically challenging times.
Why does one octopod only retain a swim bladder .... or is it a derived state? Perhaps we should experiment with the likes of Ocythoe. Perhaps I'd best get back to work and figure out how to keep these animals alive, happily, in containment.
Whoa, we are REALY getting off topic here . But, since we are... As far as the traits being recessive or dominant I have no idea. But, expression of a trait is based upon whether a gene is dominant and its overall frequency within a given population. And, there cannot be a suppressing factor involved.
As far as how you shut down and turn on gene sequences, its all dependent on activation of regions of DNA called "start" and "stop" codons. These are regions that tell enzymes where to begin and end reading and coding information. Kinda like regions of information on a hard drive, except you don't have to defrag it!
Mind you, genes also can be linked, meaning that one gene affects the expression of another or more. Also, there is incomplete dominance and co-dominace. And mutation... Wow.
Yeah... Its a mess.
A few years ago PBS ran an episode of "NOVA" called "The Real Jurassic Park", where they discussed the concept of essentially "reverse-engineering" dinosaurs from birds on a genetic level over several generations. Interesting theory, albiet a weird one. Evolution is supposed to be a one-way process for a reason, given mutation, gene frequency, and directional selection.
Steve, I know what you mean. The real issue here is not whether or not we can reverse enigineer a ceph but rather how we do it. It would involve EXTENSIVE gene mapping, and a high degree of work over several ceph generations. And in the end, would it realy be an ammonite, or some mutant mixture of man-made animal?
Troubling times indeed.
So, on a more light note, about the swim bladders: Its still not a ceph asking me for raspberry sake, so I'm safe! Dude, what's next, a pulmonate ceph? (Really stretching for that squibbon)
..... will respond soon - just a complicated question. In brief, yes, but I need to speak to a colleague in order to get the references (there is some very interesting work being done, but it goes well over my head) - I believe it is rather recent work.