why don't octopus and other cephlapods live very long?

[squidink]

as the title says whats the reason biologically speaking why they don't live very long? i'm not talking about after they breed they die because even without mating they don't live very long do they, i had been informed on another forum it is because they have a high metabolic rate "Their cells turn over molecules more quickly, metabolizing sugars and fats and proteins in order to grow quickly. All of that rapid action leads to the production of free radicals and oxidative damage."
is this correct? and if so is there a way we can slow don't there metabolism?

 

[neurobadger]

They have a gland behind their eyes that, upon reproduction, causes them to age and rapidly die.

If you cut out that gland, they can live about twice as long.

Slowing down their metabolic rate might kill them. I don't know. Perhaps someone should experiment with feeding their octopus antioxidants.

 

[skywindsurfer]

Herbal extracts and green tea? lol

I read somewhere that a scientist did remove some gland or organ in the attempt to make them live longer but was unsuccessful.

 

[DWhatley]

Sadly, I don't know the credibility of this source (colorado.edu) and will continue to look for the study I last found but this outline contains a summary of what I found in a published study (I have read either the full or abstracts from 2)
http://www.colorado.edu/intphys/iphy4480tsai/Lecture26.html

Here is an abstract that summarizes the same thoughts and sites lab work done in 1930, 1956, 1959 and 1977.

Ahh, Here is the 1959 paper, HORMONAL CONTROL OF SEXUAL MATURITY IN OCTOPUS. The experiments were designed to force sexual maturity but they removed the optic gland from several octopuses and found that known procedures for rapid sex organ growth failed when the gland was removed. Page 21 discusses optic gland removal and the results. On rereading the article, this comment was interesting and I wonder if anyone has experimented with the light aspect:

It is concluded that maturation of the gonad is determined by secretion from
the optic glands which is normally held in check by an inhibitory nerve supply
from the subpedunculate/dorsal basal lobe area. The action of this region is in turn
dependent upon the integrity of the optic nerves and thus, presumably, upon light.

Later work found that removal of the optic gland extended the octopuses lives (Hoping Level Head will jump in here as I know he has read the later work and may have a ready reference). From what I remember, not only can the gland be removed and stop sexual maturity but a small piece can be reintroduced and will start up the reproductive cycle.

 

[Level_Head]

On rereading the article, this comment was interesting and I wonder if anyone has experimented with the light aspect:

Later work found that removal of the optic gland extended the octopuses lives

(Hoping Level Head will jump in here as I know he has read the later work and may have a ready reference). From what I remember, not only can the gland be removed and stop sexual maturity but a small piece can be reintroduced and will start up the reproductive cycle.

You've covered the ground well, it seems. There is a good collection of references on this thread:

http://www.tonmo.com/forums/showthread.php?6556-Senescence-and-the-Optic-Gland

On the light aspect, your first outline contained an interesting line:

# Removal of the optic gland and bright light prevent sexual maturation of these animals.

I've read suggestions that the timing of the light is likely to influence the optic gland, but this was the first time I'd see this idea: that bright light keeps it from maturing.

Is that "all the time"? 24 hours? What effect does that have on the animal's lifespan?

I'm still jamming on a project, but that's worth some studies.

You and I have discussed the possibility that tank lighting may be responsible for the shorter-than-natural lifespans of some octopuses in captivity.

The antigen aspect was interesting, too; the idea that the optic gland is tied in to the immune system in some manner, such that the optic gland starts secreting in reaction to foreign proteins in the animal's blood.

That work was done decades ago, and our molecular capability has dramatically improved since then, but I haven't seen an update.

To address SquidInk's original question, I note that some researchers suggested that it was rapid metabolism that caused the short lifespan -- and we now know that this isn't completely true, since we can shorten or extend that lifespan without changing the metabolic rates.

It is apparently a literal case of planned obsolescence. Or, in this case, programmed senescence.

I hold out hope that evolution can make changes here. After all, a fairly close relative of the octopus (the geoduck clam) is known to live for nearly two centuries.

While we don't think of clams and cephalopods as close, the metabolism at the cellular level is in some ways more alike than different. And their body plans have surprising similarities.

 

[squidink]

very interesting. would be great if somehow we could get our octopus to live longer

 

[DWhatley]

After all, a fairly close relative of the octopus (the geoduck clam) is known to live for nearly two centuries.

With that kind of lifespan one assumes low birth rate and it is a wonder they have not become extinct from predation by humans since they are eaten in China (and likely other asian countries but oddly not in the US).

The linked article mentions aquaculture so I am a little surprised we don't see them in the aquarium hobby.

 

[Level_Head]

With that kind of lifespan one assumes low birth rate and it is a wonder they have not become extinct from predation by humans since they are eaten in China (and likely other asian countries but oddly not in the US).

The linked article mentions aquaculture so I am a little surprised we don't see them in the aquarium hobby.

Oh, they are definitely eaten in the US. You can buy them at seafood counters in the Pacific Northwest, where they're farmed:
Geoduck Recipes

 

[DWhatley]

I will have to look for them at the international market seafood counter (they are not in local grocery seafood counters and I have noticed some US food at the interantional marked). I think I would have seen them there though since I am always looking for new foods for the octopuses or live things to try in the aquarium. A an inch a year I would need to find a smaller than eating size one at the market if I wanted to try one in a tank and they are too expensive to feed the octopuses.

Birth rate must not be too low though since they are a 4 year investment and make money for the growers.

 

[Level_Head]

as the title says whats the reason biologically speaking why they don't live very long? i'm not talking about after they breed they die because even without mating they don't live very long do they, i had been informed on another forum it is because they have a high metabolic rate "Their cells turn over molecules more quickly, metabolizing sugars and fats and proteins in order to grow quickly. All of that rapid action leads to the production of free radicals and oxidative damage."
is this correct? and if so is there a way we can slow don't there metabolism?

It occurs to me that we have not addressed your original questions, and got sidetracked into the very interesting discussion of optic glands, which don't have an equivalent in mammals as discrete glands. The secreting neurons involved in vertebrates are apparently more broadly distributed.

Let's break your questions out a bit, and see if any experts here want to take a shot at them. I'm going to separate out the hidden assumptions as separate questions for clarity.

And throughout all of this, let's agree to use "cephalopods" as a shorthand for "cephalopods in general" -- while recognizing that this encompasses a pretty broad range of animals, lifestyles, and adaptations. Few laypersons would suggest that the half-inch male blanket octopus has much in common with the ten-meter colossal squid, the shell-bound nautilus, or the flap-winged little dumbo.

But the differences may help answer some of the questions:

1. Do cephalopods have a high foodmass conversion rate?
2. Does a high food conversion rate shorten cephalopod lifespans?
3. Is foodmass conversion rate the same thing as the metabolic rate?
4. Do cephalopods have a high metabolic rate?
5. Is the cephalopod's high metabolic rate the cause of their short lifespan?
6. How do cephalopod metabolic rates compare with other animals?
7. Do cephlopods have a high production rate of free radicals?
8. Do cephalopods show evidence of high oxidative damage?
9. Do cephalopods show the effects of aging in a way we relate to oxidative damage?

===|==============/ Level Head

 

[Level_Head]

1. Do cephalopods have a high foodmass conversion rate?

This question, at least, has a clear answer: Yes.

Many studies such as this one have documented that cephalopods in general, and octopuses even more than squid, have among the highest known foodmass conversion efficiencies:
Energetics: The Costs of Living and Reproducing for an Individual Cephalopod on JSTOR

And this study, downloadable as a PDF, looks at how different individual octopuses can be, even siblings from the same clutch of eggs. In some cases, their food conversion efficiency exceeded 100%:
http://eprints.utas.edu.au/9741/3/03chapter2.pdf

Octopuses are considered to have the highest conversion percentage among invertebrates — which begs the question, "What about vertebrates?"

 

[DWhatley]

Tomorrow I will see if our state University provides any kind of subscription access to jstor for either state residence or alumni as I would like to read the rest of the first publication and my uni was in the list of GA subscribers (as well as one high school. It is interesting and encouraging that a high school subscribes to this kind of publication outlet).

The second seems only to show one thing, octopuses grow as differently in an aquarium environment as they do in the wild. For hobbyists, this is actually sort of a reassuring concept that suggests tank life does not alter their natural growth. One other hobbyist interests observation that was officially noted was the change in food intake over different periods. It would have been nice if they could have documented something going on at these fasting periods but the fact that they are noted in a species we do not commonly keep in the hobby suggests it is common with this sized animal (medium sized octo with 2' arm span).

 

[devi]

Can't remember where I read this, but isn't it also known for them to live longer if you feed very little? As in near starvation levels?

 

[neurobadger]

This question, at least, has a clear answer: Yes.

Many studies such as this one have documented that cephalopods in general, and octopuses even more than squid, have among the highest known foodmass conversion efficiencies:
Energetics: The Costs of Living and Reproducing for an Individual Cephalopod on JSTOR

And this study, downloadable as a PDF, looks at how different individual octopuses can be, even siblings from the same clutch of eggs. In some cases, their food conversion efficiency exceeded 100%:
http://eprints.utas.edu.au/9741/3/03chapter2.pdf

Octopuses are considered to have the highest conversion percentage among invertebrates — which begs the question, "What about vertebrates?"

Raises the question! RAISES THE QUESTION!

Probably rodents.

 

[Level_Head]

This is actually a common (now) observation in mammals, and has been supported in a number of studies in animal models ranging from rats to human. I am not at all certain that it applies to cephalopods, though.

Moreover, the hunting of live food has been shown to increase the animal's lifespan, by keeping them actively interested in their surroundings. A bored octopus tends to live a short time, and will become neurotic and self-destructive.

I suspect that an active hunter needs such stimulation, which many keepers address in part by providing interesting toys to play with. These seem to help, too.