Flounder Mimicry in an Atlantic Octopus

Octopuses are well known for their ability to camouflage with their environments and, at times, mimic other marine species. A lack of rigid structures in their bodies makes them extremely malleable while command of their coloration allows them to easily blend in with their environments. Muscular and freely bending arms allow them to move in a variety of different ways. These features all contribute to the ability of some octopus species to use mimicry as a method of defense and survival.

 A study published by Hanlon, Watson, and Barbosa describes the first instance of documented flatfish mimicry in an Atlantic octopus species. A few examples of mimicry in octopus species had been observed previously, but the species involved had all been located in the Pacific Ocean rather than the Atlantic. The octopus Macrotritopus defilippi is Caribbean octopus that can be found in sand plains where little shelter is available. Growing up to 90mm in length, details about the biology and life history of this species remain elusive. Over the course of several dives, M. defilippi was observed in five different locations mimicking posture, style, and speed and coloration of a common flounder, Bothus lunatus.

M. defilippi

Octopuses – and other animals that use camouflage – can blend in with their environments as long as they stay still, but movement will alert predators to their presence. While some octopus species can work around this using slow movements in a dense and structured environment (such as a coral reef), M. defilippi has no such luxury. This species faces the challenge of needing to navigate a wide and open habitat without being detected. By combining camouflage and mimicry, M. defilippi can safely cross the sand without raising suspicion.

Figure 1: Examples of M. defilippi using mimicry in its movement.

Using gathered video data, the swimming speed and style of M. defilippi was compared to B. lunatus. The flounders have a distinct swimming style in which they swim along the contours of the sand, hugging the ripples. The octopuses copied this style, swimming along the shapes of the sand just as the flounders did. The octopuses also positioned themselves in such a way that their eyes were in a position similar to where the flounders’ would be. A M. defilippi octopus captured during its planktonic stage and raised in captivity in 1978 with no exposure to flounders exhibited identical swimming behavior, indicating that it is instinctual rather than learned.

Up to this point, octopus defense strategies against predators have been categorized into three stages. First is using camouflage as a primary defense, second is using sudden and startling displays when closely approached by a predator, and third is attempting to escape using erratic movements that will confuse the predator. With camouflage being the primary defense mechanism, developing a method that can maintain the illusion during quick movements is both important and difficult. The authors believe that M. defilippi being the third recorded octopus species to utilize flatfish mimicry means that using mimicry along with camouflage may be more common than previously thought and should thus be added to the category of primary defense.

Hanlon, R. T., Watson, A. C., Barbosa, A. A 'mimic octopus' in the Atlantic: Flatfish mimicry and camouflage by Macrotritopus defilippi. The Biological Bulletin 218:1 (2009). 15-24.
http://www.journals.uchicago.edu/doi/full/10.1086/BBLv218n1p15

Monsters and Mysteries of the Ocean

For many years people have considered the ocean to be a vast mystery of interesting creatures. Dating back to Greek mythology, Hercules battled with a hydra and today the living relative of hydras are octopi. An octopus is such a unique animal, that comes in many different forms. As seen in the earlier post about the octopi, the video shows how fascinating the monsters of the sea can be. Just as they can be fascinating some do come with a slight fear of the power these massive creature hold. The giant squid for example can look "snake-like, with a large head and shaggy mane," and for sailors can be intimidating. Marine biologists Rui Rosa, of the University of Lisboa, Portugal, and Brad Seibel, of the University of Rhode Island have been researching the squid and discovered that it may not be the monster the world perceives it to be. A squid can measure longer than a school bus and can weigh up to half a ton! A perfect suspect for a monster yet the researchers say that there is nothing to fear from a squid because they are basically a massive blog. The amount of energy it takes for a giant squid to be aggressive is close to impossible. This monster moves extremely slow and live in some of the deepest parts of the ocean; close to 6,000 feet under the Antarctic Sea.  

Many ships can and have been overturned by the massive so called monsters. It is said that in the 1860's a animal similar to a whale shark caused the loss of some sailors. This could be due to the shark causing the boat to either flip over, or the shipmates all jumped off in fear. New research in understanding fossilized shark teeth have lead to advancements in understanding these monsters of the sea. The fossilized teeth as well as stories from history help provide information as to what sailors really did see. In 1875 it is said that a "a sperm whale with a snake-like creature wrapped around it's mid-section" was seen. The crew reported this sea serpent eventually dragged the whale down to it's death. With a better understanding of the ocean it is thought that what these sailors saw was a squid battling a whale, seeming highly possible.
There are many creatures of the sea that could be considered monsters. We have yet to discover many of the monsters of the sea. There is so much yet to discover about the sea. As the we learn more about these monsters the sharks, octopi, and squids the ocean becomes more and more interesting!


 


  http://marinebio.org/oceans/mysteries/

Is that an Octopus Walking?

Like a sea monster, the octopus (Octopus aculeatus) walks along the benthic floor while maintaining its camouflage as a piece of algae.  This specimen was captured, along Australia's Great Barrier Reef, and was used in a study carried out at Berkeley.

Could it be possible that octopuses can stroll around on two arms?  An octopus has eight arms total and recent research done at Berkeley has shown that octopuses can use two of those eight arms to run across the ocean floor as a adaption to predation.  Two species of tropical octopuses have developed this trick where they pick up six of their legs and walk or run backwards on two of them to easily escape predators.    

The first report of bipedal behavior in octopuses, was written by University of California, Berkeley, researchers, and will be published in the March 25th issue of Science.

In Indonesia, an example of bipedal movement was found in the coconut octopus, commonly referred to as this because it looks like a coconut.  The coconut octopus can be found tiptoeing along the ocean bottom having six of its arms wrapped around its body, while two are touching the ground.  The octopus is able to use the outer halves of their two back arms like tank treads when walking along.  They alternately lay down a sucker edge, located on their arms, and roll it along the ground to propel themselves forward.

The coconut octopus is found to live on sandy bottoms in water 20-30 meters deep.  They live among sunken coconuts and sometimes even hide in the shells of the coconuts to protect its self from predators.

The other octopus that was studied in the laboratory was able to propel itself backwards.  A graduate student from the University timed the two octopuses to see which was more adapted to this new trick that has evolved.  The coconut octopus moved forward at a rate of two and a half inches per second, while the other octopus moved backwards at five and a half inches per second.  These speeds are faster than they can crawl around, but slower then when they swim (jet) around.

The Indonesian Octopus, Octopus marginatus, scoots along the ocean floor using the tips of its arms and their suckers.

The other type of octopus that can camouflage itself as algae in tropical waters looks like a sea monster walking along the sea floor with two legs, just as the coconut octopus.  This octopus is the one at the beginning of the post, known as Octopus aculeatus.


 Octopus (abdopus) aculeatus, was found to have a head the size of a walnut and it inhabits intertidal zones, with sandy bottoms, living among grasses and hiding out in tide-pools or burrying itself in the sand at low tide so it does not dry out and get stuck on shore.  To camouflage itself, it has been seen to coil its front (2) arms and raise them in a pose to resemble algae.

The researchers at Berkeley believe that the bipedal walking strategy evolved in these two octopuses to backpedal away from predators while remaining camouflaged.  Octopuses can camouflage themselves by changing their color and shape.  Normally, when octopuses are startled they cannot move away and stay camouflaged at the same time, but with this walking behavior they can do both at the same time.

The octopuses can change shape readily because they are basically a water-filled balloon, but their fluid is contained within muscles cells rather than an open cavity.  Octopuses keep their shape due to hydrostatic pressure (hydrostatic skeleton or hydrostat).  They do not contain an external or internal skeleton, that is what the pressure is for.  For movement of octopuses they normally push and pull their suckers on their eight arms or jet backwards through the water (jet propulsion).  These movements are done through the muscles that squeeze and bend the fluid filled arms and body.

In Conclusion:

The two octopuses that are found to walk along the bottom of the sea floor and their ability to camouflage relates to the idea of predation covered in class.  This new evolved trick, can help the octopuses get away from the predators, while still being camouflaged.  These adaptions can help the octopuses to survive and this can lead to zonation and other effects in the food chain and water column.

Berkeley Research Article

Sea lion VS Octopus

Usually when you think of a sea lion, you get an image in your head similar to the one I get.

That was why I was surprised to find this video from National Geographic’s “Critter cam” called Sea Lion Attacks Octopus: An Epic Battle.
I had thought that it would show an octopus attack a sea lion pup, with an adult sea lion coming to the rescue. What it does show is a sea lion repeatedly attacking an octopus, trying to eat it. Ignoring the ink-spraying defense mechanism, the sea lion keeps dragging the octopus to the surface to gain the advantage in the fight.

Video:
Sea Lion Attacks Octopus: An Epic Battle

This video proves the cold fact that nature is not always cute and cuddly. Sometimes it is a cold, indifferent battle to the death for survival, where only the fittest comes out on top.

Source: National Geographic’s “Critter cam”