An octopus is one of the most intelligent non-human species on Earth, can manipulate objects, and has lots of other interesting adaptations (e.g. the ability to change color). But, an average octopus has a life expectancy of less than five years.
What evolutionary adaptations could cause the average octopus to have a longer lifespan of 40 years or more on average?
Octopuses, or at least the bigger examples of octopuses like the giant pacific octopus, are fairly big, and really smart. Those are usually the hallmarks of an animal with a fairly long life, but octopuses live fast and die young for one major reason: they devote their lives (or rather, the end of their lives,) to protecting a huge number of eggs, which then hatch and drift up to the surface, where they effectively live as plankton. Since parenting stops when the eggs hatch, it makes sense, from a reproductive fitness standpoint, for octomoms to work themselves literally to death protecting their eggs and ensuring that a high percentage of them hatch.
If young octopuses, rather than drifting free, were intensively cared for by their parents, who actively protected them and hunted to provide them with food, there would be strong evolutionary pressure for parents to remain fit and healthy, at least until their young were relatively mature.
Parental protection and feeding would also provide a strong motivator for females not to kill and eat their mates. While, for a single female, guarding her eggs until they hatch without eating means that a single large meal is more important than a second parent, if octopuses needed to actively hunt to ensure the survival of their young, there would be a strong pressure for cooperative parenting to evolve. For males, at least, this would lead to significantly longer life spans.
Another behavioral change that could lead to longer life spans would be group living, particularly if the octopuses were able to cooperatively defend each other and their young. Octopuses living in such and environment would stand to benefit from the presence of larger octopuses to protect them from attacks, and if some sort of long-distance signalling were evolved, would also have a greater ability to spot and avoid predators.
Octopuses are also capable of learning from one another. In group-dwelling octopuses, it might make more sense for individuals to have long life spans, in order for young to more effectively learn how to survive in their environments.
Larger animals tend to live longer. Obviously, it takes longer to mature to a larger size, so as the animal gets larger, it will take longer to reach its sexually mature size. The creature will then undergo whatever adaptations it needs to so that it lives longer.
The smarter a creature is, the more it can learn in its lifetime. If a creature then applies this intelligence to increase it's survival chances, the creature's evolution will point it in the direction of longer life, because more accumulated knowledge will be more useful. A more intelligent creature will evolve to live longer.
The Pacific Giant Octopus females stop eating to monitor their eggs after they are laid. Then they die. This is obviously not conducive to a long life. In order to have long lives, female octopuses should evolve to be able to breed and lay eggs more than once. Perhaps they can form pairs and have the male octopus help watch the eggs.
You need to entirely rework their circulatory and respiratory systems, take it easy, and watch the salt.
Even though it's already at around 40-50 beats per minute (humans average 60), make their hearts beat even slower. That's going to be tricky though, because octopi have some pretty funny stuff going on with their circulatory system.
Common octopi have three hearts, one on each gill and one main one. For [reason?] the main heart stops when they swim around. Because of this, they have to store some backup oxygen in large blood sinuses behind their eyes and in their gut, for in cases of "physiological stress".
The octopus’ heart rate does not change significantly with exercise, though temporary cardiac arrest of the systemic heart can be induced by oxygen debt, almost any sudden stimulus, or mantle pressure during jet propulsion. Its only compensation for exertion is through an increase in stroke volume of up to three times by the systemic heart, which means it suffers an oxygen debt with almost any rapid movement. The octopus is, however, able to control how much oxygen it pulls out of the water with each breath using receptors on its gills, allowing it to keep its oxygen uptake constant over a range of oxygen pressures in the surrounding water. –Wiki
Don't make it have to swim around too much.
That might sound like a no-brainer, but it is especially important to octopi because of their means of locomotion via the location of their gills, and the oxygen requirements of a high functioning brain. Although they have an exceptional ability to extract oxygen from water through their gills and their skin, the efficiency of their circulatory system (and in turn, their respiratory system and cognitive ability) is inhibited when they swim.
the octopus uses a jet mechanism that involves creating a much higher pressure in their mantle cavity that allows them to propel themselves through the water. As the common octopus’ heart and gills are located within their mantle, this high pressure also constricts and puts constraints on the various vessels that are returning blood to the heart. Ultimately, this creates circulation issues and is not a sustainable form of transportation, as the octopus cannot attain an oxygen intake that can balance the metabolic demands of maximum exertion.
crawling increases metabolic demands greatly, requiring they increase their oxygen intake by approximately 2.4 times the amount that is required for a resting octopus.
Shadwick and Nilsson concluded that the octopus circulatory system is “fundamentally unsuitable for high physiologic performance.”
–Wiki
Make it as big as possible.
As animals get bigger, from tiny shrew to huge blue whale, pulse rates slow down and life spans stretch out longer, conspiring so that the number of heartbeats during an average stay on Earth tends to be roughly the same, around a billion. –kottke.org
Can you think of an appropriate environment that would be safer?
They are exposed to a wide variety of temperatures in their environments, however their preferred temperature ranges from about 15 °C to 16 °C. They have an acceptable ambient temperature range of 13-28 °C, with their optimum for maximum metabolic efficiency being about 20 °C.
The receptors on its gills allows it to keep its oxygen uptake constant in a wide range of oxygen levels in the surrounding water, so that you can play with, however
It has been shown that octopuses have an average minimum salinity requirement of 27g/L, and that any disturbance introducing significant amounts of fresh water into their environment can prove fatal.
This likely complicated by the fact that
they are conformers. This means that they adapt to match the osmotic pressure of their environment, and because there is no osmotic gradient, there is no net movement of water from the organism to the seawater, or from the seawater into the organism.
An octopus is an intelligent creature, stuck with a "reproduce once, lay thousands of eggs, and then die" life cycle. To benefit from a longer life and evolve to have one, a lot would have to change. Of course what you'd choose to include in a story is up to you.
Let's start simple. For a male octopus to live longer, he may just need a mutation that deactivates (or fails to activate) the "death genes" after mating. Then he may be able to live as long as he can avoid being lunch or any kind of injury. So if you just want one octopus swimming around, contemplating the cruelty and wonder of life for years, you're done. But for the mutation to spread, of course it would need to give his offspring some advantage.
A female octopus lives for a time after laying her eggs, to protect them and fan water over them so they have enough oxygen. She does this to the exclusion of feeding herself (perhaps she has death genes, as well, so feeding is irrelevant). To live longer, as it is now, she'd have to abandon her eggs (or at least care for them less). Of course that's not an advantage, and may stop her genes from getting into the next generation entirely.
If they became cyclic maters, and cared for the eggs together, that would bring more of their genes into future generations. But there's a reason they don't live that way now. Too many would strain the food supply. And an octopus lives a solitary life, avoiding predictors through cunning and stealth—too many in an environment would make predictors more familiar with their tricks.
So unless they somehow happened to find an environment that had no predators and lots of food, they'd need to deal with both food and safety in very different ways. Perhaps it's my species bias, but I tend to think of ways to do this that would mimic human advancements.
Manipulate the coral to grow into protective structures. Promote growth of other species, like farming. Form a symbiotic relationship with another species, like we did with wolves, to help protect the underwater structure and farm from predictors. I don't know what an octopus could bring to such a relationship, but they are much better at escaping than fighting, so they'd need muscle. Obviously they'd need to be social to do all this, and learn to communicate.
Octopus can manipulate the environment. They are strong, and smart. But I doubt they could evolve this way. For one thing, they don't have stamina, and building and maintaining such a system would take a lot of work. They have copper-based blood (like a Vulcan); it evolved to deal with the pressure at depth. Compared to our blood, it is less efficient at carrying oxygen, and it is thicker and harder to push around their circulatory system. So they tend to expend energy in short bursts, and then they are exhausted.
So I'm not really sure what natural conditions would allow them to benefit from a long life. Perhaps if a new sea opened up, an octopus with multiple mating cycles would help fill up their niche faster, but the situation would eventually stabilize and be similar to existing seas.
I keep thinking it would have to involve another species, to evolve naturally. Perhaps if they developed a very close symbiotic relationship, they hitch a ride and get protection in exchange for pulling off lampreys and companionship...? Intelligent creatures on land seem to have some recognition of other intelligent creatures, and sometimes reach out to them. But intelligent land animals are already social, so an octopus may not think this way.
I hope that gives you some ideas to work with.
There are two ways to envolve based on the dangerous-level of the enviroment:
PD: Also I am agree with the kingledion answer.
