The ocean is filled with thousands of interesting creatures whose behaviors have intrigued scientists and curious minds around the world for years. One group of these remarkable creatures are octopuses, consisting of over 300 species, known for their intelligence, problem-solving skills, and tragic phenomenon: self-destruction.
Many species of these soft-bodied, eight-limbed cephalopods take their own lives after reproducing. But why do these creatures, so evolved and intelligent, seem to take their own lives? Let’s have a look at the perplexing mystery behind this self-destructive behavior.
Octopus Intelligence
Did you know that octopuses have the most brains among invertebrates? Unlike many other animals, they grow up and learn by themselves, with no help from their parents. This makes sense since their parents are often dead before they are even born! These majestic animals quickly learn how to hide and camouflage to avoid interactions with predators.
Eight Limbs, Nine Brains
As if these eight-limbed creatures weren’t interesting enough, they impress us further by sporting 9 brains. Yes, nine! Unlike most animals, they don’t have a centralized brain. Instead, they have one mini-brain in each of their eight tentacles with around two-thirds of their neurons also located in their limbs. Through this decentralized nervous system (the system that sends messages back and forth between the brain and the body), each of their mini-brains allows each tentacle to function and process information independently. Allowing each limb to perform complex tasks like exploring, manipulating objects, or reacting to outside stimuli without direct input from the central brain. This is also the reason these cephalopods have such sharp reflexes!
Central Brain
Their ninth, and highly developed larger central brain oversees their entire nervous system and can even override their mini-brains to operate their tentacles when needed. The central brain has large optic lobes contributing to octopuses excellent vision and spatial memory.
Proven Intelligence
The combination of their distributed nervous system and sophisticated central brain allows these incredible animals to show remarkable problem-solving skills, learning capacity, and at times, even playful behavior. Octopuses proved their intelligence time and time again by exhibiting behaviors like using tools, solving puzzles, and even escaping from enclosures. Yet, despite their brilliance, they have a shockingly short life span, some species only living between 1 and 2 years.
This short lifespan is mostly due to their reproductive cycle, which marks the beginning of the end for these sea creatures. For most octopus species, reproduction is a once-in-a-lifetime event that triggers the start of their rapid decline.
Reproduction
Octopuses are semelparous animals, meaning they only reproduce once in their lifetime and then die. After mating, female octopuses lay their eggs in a den and dedicate their entire existence to guarding and caring for their eggs.
It is during this time that their decline begins. She stops eating as her sole focus lies on the survival of her offspring. Once her eggs hatch, sometimes even before, her body starts to deteriorate leading to what appears to be intentional self-harm and eventually, death.
Longest Brooding Period Ever
But don’t think that this is always a quick process. One incredible Deep-Sea octopus, scientifically known as Graneledone boreopacifica, was observed in the Monterey Canyon brooding her eggs for 53 months – the longest brooding period ever recorded in the animal kingdom! This means that she took care of her eggs for longer than most octopuses live for, while not leaving her eggs unattended for one second.
Process of Self-Destruction
This process where octopuses exhibit strange and distressing behaviors is known as senescence. During this time they become disoriented, lose their motor control, and inflict wounds on themselves, such as tearing off their skin and limbs.
Some octopuses also completely stop taking care of themselves and lose their appetite entirely. As the process of senescence progresses, the octopus’ body deteriorates until it dies, often before even meeting their offspring.
The Reason Behind Senescence
But, before you start to think that octopuses are ending their lives due to being unhappy there is a scientific reason behind their behavior. These eight-limbed animals have a small gland called the optic gland responsible for this odd behavior.
The optic gland controls the release of their reproductive hormones, and after an octopus lays eggs it releases a cocktail of hormones that triggers their senescence. Making this gland the reason behind their self-destructive behavior.
Catch 22
Interestingly, studies have shown that if the optic gland is removed from an octopus, the self-destructive behavior stops and the octopus continues living. However, without this gland, they cannot reproduce! This discovery proves the biological nature of this strange behavior, rather than it being a conscious choice.
Naked Mole Rat Senescence
Senescence can also be described as biological aging, and the rate at which animals undergo this process in the animal kingdom varies immensely. For instance, if we look at the naked mole rat who lives for around 30 years, their senescence is unusually slow. Despite their significant lifespan, naked mole rats show little to no signs of aging when it comes to their metabolism, reproduction, and mortality risk. In other words, they hardly age as the years go by!
Pacific Salmon Senescence
On the other hand, the senescence of Pacific salmon is remarkably quick – just a couple of days to weeks after spawning, or laying their eggs! Once Pacific salmon are done with their upstream journey and reproduce, hormonal changes trigger their internal decay causing tissue breakdown, organ failure, and immune system decline. Some of the more visible signs of these fish’s physiological deterioration include skin discoloration, lesions, and muscle wasting. Interestingly, much like the octopus, Pacific salmon also only reproduce once in their lifetime before their senescence is triggered.
Evolutionary Biology
If you look at it from an evolutionary standpoint, the idea of self-destruction might seem counterintuitive, right? However, it is believed that this behavior ensures the survival of their offspring. But, how?
By the female octopus dedicating all her resources to caring for their eggs and then dying, she gives her offspring the best chance of survival. Her passing means that her offspring has less competition for food, ensuring them a better chance of survival.
Do All Octopuses Self-Destruct?
Although most octopus species undergo the process of senescence, it is important to note that not all species exhibit this extreme behavior. Some species have different reproductive strategies and their post-reproductive behaviors vary.
However, many well-known species, like the common octopus, scientifically known as Octopus vulgaris, follow this cycle of reproduction and self-destruction.
But, Is It Suicide?
When seeing or learning of this behavior, it is easy to anthropomorphize and think of it as suicide. Yet, it is crucial to differentiate between the human idea of intentional self-harm and the biological process driving these octopuses.
For these incredible animals, it is a predetermined, evolutionary process and not a conscious decision. And while it might appear incredibly sad, it’s simply the way nature has programmed these animals to ensure the next generation’s survival.
Conclusion
The perplexing mystery of these wonderful sea creatures’ self-destructive behavior is rooted in the intersection of biology, evolution, and survival. While this process of senescence may seem grim, it highlights the fascinating ways in which nature has adapted different species to thrive in their different environments.
While understanding the science behind this seemingly odd phenomenon, it helps us understand and appreciate the complexity and wonder of these remarkable creatures. The next time you see or think of an octopus, remember that even in their final act, they are driven by purpose embedded deep within their biology.
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