Discussion in 'Physiology and Biology' started by neurobadger, Apr 29, 2011.
Do we know what actually gets secreted from the optic gland?
Optic gland juice.
More seriously, a gonadatopic hormone. The optic gland has a nerve that is used to inhibit the production of this hormone -- so cutting the nerve causes the cephalopod to start aging (and dying) rapidly.
Removing the optic glands, though, can greatly extend their lives:
This effect figures into my novel; the octans (descendants of octopuses) are just learning about surgery.
The optic gland hormone -- a type of steroid -- is indicated here as being part of a foreign protein defense mechanism:
I just watched an interesting Smithonian video on aging/cell life that would be really interesting to combine with a study on this process. If you choose to watch it, allow time for the whole program as seeing only part does not give the full story of what they are finding.
Several reactions. I'm fairly familiar with telomere research (though I confess that I've never pronounced it like that) -- and this was interesting. And annoying at the same time: Some 90% or so of the visuals were stock footage of traffic or old movies or other such things -- this is packaged at low information density.
But at least there were no commercials!
The optic gland hormone, so far as I know, has no connection with telomeres in its operation. The eyes are wired to the brain and to the optic gland by a fairly visible nerve -- as long as the nerve is generating a signal to the optic gland, it remains mostly inactive. (Though it does seem to have a defensive role in the cephalopod immune system.)
But once the eye and brain decide that the light pattern of the day meets a certain criteria, this nerve signal changes or stops -- and the optic gland starts doing its thing. The animal become rapidly sexually mature, and pursues reproduction -- and ultimately, death.
We've speculated, you and I, that changes in the lighting pattern from natural environment to tank lighting may trigger this process -- which means that, once we figure out what the right "not time yet" lighting is for a particular species, we might extend their lives greatly in aquaria.
And surgical removal of the optic glands has been shown repeatedly that lifespan can be greatly extended -- and the maturing process and behavior even reversed somewhat. Just as cutting those nerves brings an immediate onrush of sexual maturity, even in animals too young. It doesn't always work, of course -- there's such a thing as too young -- but the body tries its best.
So far as I know, humans do not have an equivalent mechanism. But cephalopods and humans share the telomere-limiting aspect, the "Hayflick limit" -- it's just that cephalopods seem to get nowhere near this limit under normal circumstances, so it's the action of the optic gland that controls their lifespans.
My thoughts were more to see if the chemical changes brought about by the optic gland would show in the tips of the DNA cell lengths (I agree that the video lacked anything to see but the information was new to me so the audio kept my interest) BECAUSE the aging process is SO different.
Another piece in the lighting puzzle (with no place to arrange it) may be the very strange way Monty suddenly keeps his eyes closed. It appeared to happen overnight but he was reclusive for about a week before I saw his eyes. In the smaller aquarium, he will now come out and follow the walls, in the larger tank he just stayed in his den. I am not sure if this is good or bad for him but we do see him more. He will touch my hand and not jerk away but does not seek petting or handling. I have determined that he can detect light and does not like it. It may be that he is coming out now because we are keeping the tank lights off and nothing to do with the environment change.
From my reading, I would wager that the optic gland hormone (the general description is "a gonadotropin") does not affect telomere length. Except, of course, indirectly, in that it induces rapid growth (i.e. much cellular division) in gonads and other changes associated with sexual maturity -- but these are likely to be the normal "use" of those telomeres.
Monty's closed eyes are curious -- and I hope, not uncomfortable.
humm, I wonder if cell division is excellerated and they do indeed replicate to the Hayflick limit. It would be an interesting study since we so often find parallels for the basics in animals that have evolved separately (I am specifically thinking about eyes)
Yes - a gonadotropic hormone is what I found in my searching on the internet.
Rapid growth in gonads isn't going to necessarily affect it; in germ cells, the telomeres are kept intact by telomerase. (Telomerase is also expressed in tumors of some kinds.)
The only case in which I've seen an octopus keep its pupils closed was in an octopus at the aquarium I volunteered at; this was probably partially because of the conditions in which she was kept and not necessarily due to normal aging processes, plus her keepers gave her another estimated year and a half before she died.
Surgical removal of the optic gland, oddly enough, also causes sterility in the octopus whose optic gland is removed.
If the light pattern of the day meets certain criteria, wouldn't the onset of sexual maturity occur in any octopus exposed to it? I would wager that certain other biochemical criteria would have to be met; this is much the case in mammals of certain ages whose mating season is determined by environmental criteria.
Ultimately, I guess what's not answered is why this causes the octopus to die (and interestingly to me, the onset of senility in the male octopus. What goes on in the brain of a senescent male octopus? Perhaps this could have some interesting medical applications).
For everyone's benefit, this is what Wikipedia says about gonadotropic hormones in Vertebrata (I have made it a different color because the quote function is hard to read):
Gonadotropins (or glycoprotein hormones) are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates. This is a family of proteins, which include the mammalian hormones follitropin (FSH), lutropin (LH), thyrotropin (TSH) placental chorionic gonadotropins hCG and eCG and chorionic gonadotropin (CG), as well as at least two forms of fish gonadotropins.
The alternate names for these hormones are follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-stimulating hormone (TSH), human chorionic gonadotropin (hCG), and equine chorionic gonadotropin (eCG).
By the way, Level_Head, can I read what you've typed of your novel so far?
Certainly. I'd be pleased to have you read it, and perhaps it can be a pleasant distraction from life's recent unhappinesses.
The expression "your novel so far" suggests a bit of confusion. There are five novels planned in the Octans saga. Book One, Age of Octans, is complete. Book Two, Octans War, is not yet finished. That's what our mutual friend DWhatley has been nudging me on; she's read Book One.
And so can you, as soon as you pop me a private message with your email address, and whether you prefer Word or PDF format.
Separate names with a comma.