The oddest among the creatures undersea, there cannot be any other apt introduction for the blanket octopuses than this. These creatures have intrigued the scientific community, unlike any other species, and they are still on the hunt to know more about these magnificent creatures. Blanket octopuses are not easy to find because, for most of their life, they remain hidden between the nooks and crannies or on the ocean bed.
In this article, we will discuss many fascinating & jaw-dropping facts about the blanket octopus that’s going to get you on your toes!
Hop on lads, let’s get going.
Kingdom – Animalia
Phylum – Mollusca
Class – Cephalopoda
Order – Octopoda
Family – Tremoctopoclidae
Genus – Tremoctopus
Common name – Blanket octopus
Size – Males grow up to 1.5 inches & Females grow up to 6ft
Habitat – Tropical & Temperate seas
Lifespan – 3-5 years
Diet – Prawns, Small fishes, and other Cephalopods
IUCN Red List status – Least Concern
The origin of the name Blanket Octopus
Unlike other members of the octopus’s family, the blanket octopuses have sheets of flesh stretched between their arms. These sheets of meat when they spread their arms look like a blanket and thus the name, blanket octopuses
The morphological features of blanket octopuses are very different from a typical octopus. The only morphological similarity between them is the silvery tone on their sides, and the very dark purple or blue dorsal surface.
These blanket like structure is obviously not for warmth! Instead, they use this web as their first line of defense against predators. When threatened, blanket octopuses are found to stretch their arms out, creating a silhouette that is capable of scaring away the predators.
When this deceptive trick does not work out, they are capable of detaching these blankets, causing the predator to be entangled in the web giving them enough time to escape. Detaching these blankets may also happen accidentally.
These blankets are occasionally spotted by deep see divers diving in the Australian waters.
Can you imagine how a blanket of these octopuses would look floating in the water? A beautiful scarf made of living flesh, quite a fantastic sight to behold, huh?
The startling difference in size between a male and a female Blanket Octopus
Among the many factors that make the blanket octopuses one of the weirdest in the marine world is the startling difference in size between a male and female. Male blanket octopuses grow barely up to an inch while some females are found to grow to a whopping 6ft in length. The males are so small that they could easily fit inside the ladies’ pupils.
While a male blanket octopus weighs little over than what a walnut would, the female blanket octopuses can weigh almost 40,000 times more than the males. This drastic difference in size & weight is called sexual-size dimorphism.
Blanket octopuses are not the only species to show sexual-size dimorphism, but theirs is the most substantial difference found in the animal kingdom! It appears to the marine scientists and biologists that the male blanket octopuses spend the majority of their energy on finding a potential female to mate and not on growing.
Did you know that the presence of male blanket octopuses was a myth until they were seen in fishermen’s net?
Only females Blanket Octopuses have the blanket like sheets of flesh
Yeah, not all blanket octopuses have this sheets of flesh between their tentacles. Only the females have them. The reason for this difference, as stated by some biologists points to the evolution of these species.
How do Blanket Octopuses mate? ( Reproduction Behavior)
Though there are other species in the animal kingdom showing sexual-dimorphism none of them have such a startling difference as these blanket octopuses. How do they mate with such a difference in size? This question has intrigued biologist for years.
The males have a large arm known as hectocotylus in a spherical pouch on their body. These large arms are, in fact, the modified reproductive organs of the male.
When they mate, the hectocotylus detaches from the male’s body and the female keeps it in their mantle cavity until her eggs are all fertilized. Soon after a successful mate, the males are found to die as if their sole purpose of survival was to have a successful mate.
The female blanket octopuses can carry more than 100,000 eggs in a sausage-shaped calcareous secretion at the base of the dorsal arms. They carry the eggs until they hatch.
Did you know that mating happens at an arm’s length in blanket octopuses?
What does a Blanket Octopus eat? (Blanket Octopus Diet)
Diet patterns of all the octopuses are similar. Since the blanket octopuses aren’t bottom-dwelling they mainly feed on prawns, small fishes, and other cephalopods.
Predators of Blanket Octopuses and their bizarre method of defense
The main predators of a blanket octopus are large fishes and some types of whales. Since the male blanket octopus is very small they are vulnerable to attack from fishes than the females.
The female blanket octopuses unfurl their blankets in the event of a threat from a potential predator. This behavior is quite common in the animal kingdom. Generally, the bigger a prey appears, the more the predators will be suspicious and do not take a chance.
In the event where this deceptive defense doesn’t work, they can detach their blankets from their body, causing the predator to be tangled in it. The blanket of these species floating the ocean waters is a common sight in tropical & subtropical oceans (Though sighting living octopuses is difficult).
They are immune to the toxins of poisonous jellyfishes
There are quite a few tricks these guys have up their sleeve. In the case where their blanket defense doesn’t work, they don’t freak out.
Blanket octopuses are immune to the sting from the highly toxic jellyfish Portuguese man-of-war. These octopuses are commonly found to break off the poisonous tentacles from these jellyfishes and using them to fight off their predators.
Some divers have reported sighting these octopuses brandishing the tentacles of a jellyfish considering them as a potential threat.
Blanket Octopus Habitat (Where do blanket octopus live?)
They are found to inhabit in all the tropical and subtropical waters in this planet. Blanket octopuses are commonly found in tropical, temperate seas, Indo – Pacific and Atlantic Oceans coasts, Australia, and in the waters of New Zealand.
They are frequently found to live along the coral reefs and ocean floor. These octopuses make dens where they live and can stay undetected in it. Small crevices and rock bottoms are also their preferred places to visit.
Unlike the ordinary octopuses that are found to make only specific depths as habitats, the blanket octopuses are found in deep depths of the ocean floor. This creates another reason for the blanket octopuses to be considered different from their close cousins.
They lead a nomadic life
The blanket octopuses behave similarly to the ordinary octopuses when it comes to choosing their habitat. These creatures tend to find a new place to stay every 10 to 14 days. The reasons for this behavior can be attributed to their opportunistic nature.
These octopuses can survive in different water temperatures making it easier for them to adapt to the nomadic life. This ability to survive in varying temperature conditions is said to be one of the reasons for this species to have survived for millions of years.
Did you know that apart with showing sexual-dimorphism, these octopuses’ size also varies with the temperature of the water they live in? The species living in warmer bodies of water are much smaller than those residing where it is colder.
They are romantic beings
Romantic!? Yeah, you heard me right. Blanket Octopuses are very wild creatures and the epitome of selfless love. Okay, now let’s get to the point.
When a male blanket octopus finds a female, he doesn’t try to prove himself or convince her that he is the right guy. Instead, he fills up his small arm with his sperms and sticks it to her body. She can use it if she wants, no compulsion whatsoever! All he wants is her to be happy, LOL!
The little guys then break their small arm containing the sperms and swim away. These male blanket octopuses die almost soon after a successful mate.
Blanket Octopuses are intelligent species
All octopuses are intelligent, including the blanket octopuses. In fact, biologists say that octopuses are the most intelligent among the invertebrates. They can use tools, create gardens to camouflage, mimic other ocean animals, and perform tasks by watching other more experienced octopuses.
Blanket octopuses are immune to the toxins of the poisonous jellyfish, the Portuguese man-of-war. These octopuses break the tentacles of the jellyfish and are seen to use it to defend themselves from predators.
Biologists who have researched on the behavioral patterns of blanket octopuses’ claims that they have different temperaments towards specific activities and objects. This suggests that they might have different personalities or at least preferences towards certain things.
Some biologists believe that had the lifespan of octopuses been longer, they would have become one of the most intelligent and dominant ocean animals alive.
Unfortunately, they have a shorter lifespan of no longer than 3 – 5 years. A longer life span would have given them enough time to develop their intelligence and improve their abilities.
Only the male blanket octopus use the tentacle of the Portuguese Man O’ War
Though all blanket octopuses are immune to the toxins of the Portuguese man o’ war, only the males tend to use its tentacles to ward off the predators.
The teeny weeny male blanket octopus does not have the flashy blanket like structure like the female, and hence they use the tentacles from the Portuguese man o’ war.
The juvenile females also use the tentacles of the Portuguese man o’ war, but as they grow larger, they abandon this strategy. Predators of the more prominent female blanket octopuses are mainly giant sharks; do you really think the sharks would be scared of the sting? Nah, I don’t think so.
Male blanket octopuses have large eyes (Blanket Octopus Eyes)
Though the male blanket octopuses are smaller than the females, they have an evolutionary advantage that helps them easily spot a female. These male blanket octopuses have a large eye when compared to their body size.
Male Blanket Octopuses have a reproductive arm
The male blanket octopuses that are sexually matured have a large modified reproductive arm known as the hectocotylus within a spherical pouch.
When the male mates the pouch ruptures, causing the sperms to be injected into the tip of the hectocotylus (modified arm).
This arm containing the sperms is given to the female, and it remains in the female’s mantle cavity until used to fertilize her eggs. It is important to note that the males almost certainly die after a successful mate.
Did you know that the male blanket octopuses do not have the ability to regenerate the severed hectocotylus? While other octopuses can regenerate a lost limb.
Sexual selection is quite frequently seen in male blanket octopuses
Sexual selection is a mode of natural selection of mates, where a species competes with other members of the same sex for members of the opposite sex.
In simpler words, the male blanket octopuses are found to compete among themselves to mate with a female.
The females blanket octopuses have been found to contain multiple male arms within their mantle cavities. In such a scenario where the females have more sperm available for use than they have eggs to fertilize, there will be a drastic difference in the reproductive success of males creating a sexual selection.
Sexual selection is seen to cause extreme dimorphism
Sexual selection among the male blanket octopuses means that now the males have to compete among themselves for a mate.
In such a scenario, the male octopuses tend to reduce development time by maturing earlier, but this causes them to be smaller than an average male blanket octopus.
This is known as extreme dimorphism. Being small does not impede their ability to find females; they would still have a large eye compared to their body.
Some biologists also claim that natural selection may also have contributed to extreme dimorphism in this species.
Why are the female Blanket Octopuses larger? (Blanket Octopus size)
If you have a closer look at the animal kingdom, almost all the female species are more significant than the males. The reason is very simple; males do not have to be larger. There is no use in a larger male. Doesn’t make any sense, huh?
Among both the sexes, the female gives birth to an offspring. The larger the female, the larger the eggs/offspring’s she can carry.
After all the more chance you have of getting your genes into the next generation, the better. Size of the male does not matter in ensuring the sustenance of a gene because even a minuscule male can accommodate a large number of tiny male sperms.
Types of Blanket Octopuses
There are 4 types of blanket octopuses.
1. Common Blanket Octopus or the Violet Blanket Octopus
These are the octopuses that belong to the family of Tremoctopodidaes that are found in the tropical and subtropical seas, mainly in the Atlantic Ocean. In the case of this species, the females grow almost around 2 meters while the males grow only about 2.4 cms.
2. Tremoctopus Gelactus
They belong to the family of tremoctopodidaes and are found in the tropical and temperate seas. These species are found to live in greater depths than the typical blanket octopus. A distinguishable feature about this family of blanket octopus is their gelatinous body. Also, they are so transparent that you read a book through their body.
3. Tremoctopus Robsoni
These octopuses are mainly seen in the New Zealand waters.
4. Tremoctopus Gracilis
They belong to the family of Tremoctopodidaes and are seen in the Indo-Pacific waters.
The blanket octopus has three hearts & a massive brain
Similar to the common octopuses a blanket octopus has three hearts and a massive brain that’s located inside their colossal head. Each heart of a blanket octopus serves a distinct function. The systemic heart is responsible for pumping the blood throughout their body while the two branchial hearts are responsible for pumping the blood through their pair of gills.
When the animal swims, the systemic heart stops functioning, and the amount of oxygenated blood in their body drops down to an alarming rate, which is why they aren’t seen swimming rather seen effortlessly gliding.
Another exciting factor about them is the presence of a circulatory system consisting of arteries, capillaries, and veins and are lined with a cellular endothelium.
This is something that is not seen in the other invertebrates. The blood circulates through the aorta and capillary system, to the vena cavae, after which the blood is pumped through the gills by the auxiliary hearts and back to the central heart.
Though there are morphological differences between the male and female blanket octopuses, there aren’t any significant anatomical differences and hence has a similar circulatory system.
The Blanket Octopuses have blue-colored blood
Yeah, blanket octopuses are the epitome of amazement. Just like there is hemoglobin in our blood that is responsible for carrying oxygen to different parts of our body, octopuses have hemocyanin in their blood.
The hemocyanin is rich in copper and is mixed with blood plasma instead of being carried by the blood cells causing its blood to be blue in color.
The blanket octopuses are found to have high blood pressures in excess of 80 mmHg. Having hemocyanin makes the blood viscous, which means it requires a considerable amount of pressure to circulate the blood throughout their body.
The presence of hemocyanin instead of hemoglobin is an evolutionary adaptation to living in cold conditions. Octopuses, in general, are found in considerable depths in their natural habitat.
The temperature in those depths will be very less than what is on the surface, and in such low temperatures, hemocyanin can carry oxygen more efficiently than hemoglobin.
The blanket octopuses are not endangered species
Though blanket octopuses are not widely seen, it doesn’t imply to them being endangered. According to the International Union for Conservation of Nature (IUCN), most octopus species are not endangered.
In fact, it is difficult to collect data about their numbers as most octopuses live in great depths. Speaking of the blanket octopuses sighting them happens once in a blue moon. Human intervention hasn’t affected octopuses much, and their intelligence can he held a reason for it.
The blanket octopus can change color
The blanket octopus, like most of the other octopuses, have the ability to change its color at will. Their ability to observe their surroundings and change color accordingly makes them capable of excellent camouflage which is also an example of their intelligence.
Typically they have silvery sides and purple surfaces!
The Female Blanket Octopuses are highly protective mothers (caring for Eggs)
The male blanket octopuses die almost as soon as they transfer their arms containing the sperms to the female. Once the eggs are fertilized, the females can lay around 200,000 to 400,000 eggs. The female octopuses are seen to take good care of the eggs as if she is obsessed with the eggs.
The female blanket octopuses are even seen to stop consuming food while they wait for the eggs to hatch. Once the eggs hatch, the female’s body starts shutting down.
Cellular suicide happens, which causes her tissues and organs to rip apart. This continues until the adult blanket octopus dies.
The hatched eggs are called larvae, and they are found to drift in the plankton clouds. These larvae are seen eating other animal larvae until they mature.
When living in the plankton clouds, they are prone to be eaten by other species that survive on plankton. These larvae do not have a blanket like structure for defense neither is capable of using a poisoned stinger like the adults.
They are capable of absorbing oxygen through their skin (How do Blanket Octopus breathe?)
Though they have a fully developed respiratory system, the blanket octopuses can absorb additional oxygen through the specialized cells in their skin. When a blanket octopus is at rest, it absorbs almost 41% of the oxygen through their skin and while swimming it drops to 31%.
The normal respiration process involves drawing water into the mantle cavity through an aperture, passing it through the gills, and expelling it through the siphon.
The passage of water into the mantle cavity is achieved by contraction of radial muscles in the mantle wall, and flapper valves shut when strong circular muscles force the water out through the siphon.