Cephalopods and The Mimic Octopus

This topic submitted by Tim Oliverio ( olivertp@miamioh.edu) at 11:17 PM on 6/10/04.

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Cephalopods and The Mimic Octopus

The ocean is a vast body of water covering more than seventy percent of the world. In this vast body of water lies an enormous amount of life, some life that we know about and study and most that we don’t yet know of. It is important to continue to study our environment so we may gain more knowledge from our findings and that we may be able to better preserve and use it.
The “mimic octopus” is a very recent discovery made by scientists. It was so recent that an official scientific name has yet to be assigned to this organism. The “mimic octopus” has very unique behaviors in order to ward off predators and to remain safe. Octopuses are members of the phylum Mollusca and belong to the class Cephalopoda, further more they make up the genus Octopus. The octopuses’ anatomy along with its means of locomotion and many other physical features are much like other octopuses. There is one major difference; the “mimic octopus” has the ability to mimic other animals.
The octopus is an invertebrate, which means it has no bones in its body. The body is made up of a very muscular mantle and arms, which are called tentacles. The mantle gives the animal its shape and it protects its internal organs. Octopi have numerous hearts, which help to pump blood through its closed circulatory system. Branchial hearts are the two hearts that are located at the base of the gills, which help to move blood through the gills, and this in turns allow gasses and blood to be more efficiently passed through the animal.
A type of jet-propulsion system helps to achieve movement for the octopus. Circular and radial muscles make up the mantle of the octopus. Upon contraction of the circular muscles there is a decrease in the volume of the mantle cavity and valves close to prevent water from moving out of the mantle cavity between the head and the mantle wall. This forces the water to be forced out the narrow funnel called the siphon. There are muscles attached to the siphon that can help to control direction of movement. The cavity’s volume is then increased by radial muscle contraction and the process can begin again.
Octopi have an extremely advanced nervous system compared to other invertebrates. There brains are large and they form from a fusion of ganglia. Muscle contractions, sensory perception, memory and decision-making processes have a very large portion of the brain devoted to theses processes. This allows the octopus to be a very smart animal that is able to lean and problem solve. Studies have found that an octopus can learn by watching other octopi, called observational learning. Not only are octopi smart animals they also have a very keen sense of sight. As a matter of fact their sight is somewhat like humans. One-way in particular their sight is better than ours is how the optic nerve is connected. The optic nerve is connected to the back of the retina in octopi, which allows the octopi to have no blind spots. Humans on the other hand have a blind spot because of the placement of the optic nerve. An octopus can make out shapes and some colors.
When feeding, octopi use their sense of sight to find their prey and their tentacles to catch the prey. The suction cups that line the tentacles are very sensitive to the touch. The tentacles have suction cups covering the bottom side of them, which allows them to grasp onto objects. Some of the suction cups may also contain protein. The protein helps to reinforce the suction cups, and small hooks help to aid in holding onto objects. Mastication is performed with a jaw and a radula. The jaws actually tear the food and the radula grasps the food and forces it into the mouth. Octopuses hunt for snails, fish, and crustaceans. They are nocturnal hunters. In some cases venom from salivary glands help to immobilize their prey so the may eat their prey more easily.
Chromatophores are cells that contain pigment. These cells give the octopus the ability to change color depending on the mood of the octopus. Chromatophores also help the animal blend in with its surroundings so that it may be camouflaged and harder to be found. This sometimes happens in correlation with a discharge of ink from the ink gland. The ink helps to allow the octopus to escape danger. The ink blinds their predator and it can help to disorient it long enough for a getaway. The ink can also be poisonous to other animals as well as itself if exposed long enough.
Octopi are dioecious, which means there are separate male and female sex organs on different individuals. The sperm are contained in “packets” called, spermatophores. A modified tentacle of the male called a hectocotylus, which has modified suckers so that it is able to hold onto the spermatophores, transfers spermatophores. During copulation the male actually removes the spermatophores with his hectocotylus and places it in the mantle cavity of the female, depositing it near the oviduct. Then the eggs are fertilized and the female attaches them to a hard surface outside the body. She will actually keep them clean of algae and parasites until they hatch. The female helps to free the babies from the eggs by shaking and pulling away the shell. After the babies are out of the egg she does not take care of them anymore.
The “mimic octopus” was discovered in 1998 off the coast of Indonesia at the mouth of a river in Sulawesi. It is white and black striped (like a jailbird outfit) on its entire body. They grow to about sixty centimeters from arm tip to arm tip. The “mimic octopus” also feeds from the sea floor, snatching up small animals, such as fish and crustaceans.
While most of the “mimic octopus’” physical or anatomical attributes are much the same as any other octopus, there is one unbelievable ability that this animal has, mimicry. This specific octopus has the ability to portray itself as other animals to help protect itself from predators.
A banded sole, banded sea snake, cuttlefish, lionfish, and a jellyfish are some of the animals that the “mimic octopus” has been observed successful mimicking. Theses animals that are being portrayed are all venomous. The mimicking ability of this octopus is also used in correlation with its coloration to help camouflage itself. A single octopus is able to mimic all of theses animals not just one or two. When the “mimic octopus” is foraging for food it displays a very unique technique. This animal will actually enter tunnels completely, on the sea floor up to one meter deep and hunt their prey. This is the only octopus known to forage in subterranean tunnels in this manner.
Some scientists may argue that this different body formation may just be a type of courtship behavior. The thought most widely believed is that this is a defense mechanism. It is most probably a behavior that is contained in the genetic makeup of these animals and is less likely that it is a learned behavior. This is however a topic that is still being debated and studied to this day.
Survival and reproduction in the wild is the most common goal of species. Defense mechanisms of different animals help to achieve this goal. One of the defense mechanisms that some animals obtain is the ability to produce toxic venom. This venom can be used to help protect them or it can be used to aid in the task of catching food immobilizing their prey. There are a wide variety of marine animals that have this special ability to be able to produce toxic venom.
For example the lionfish has a venomous fin spine. These spines are capable of puncturing flesh and causing a great amount of pain while also releasing harmful toxins into the victim. These toxins can cause paralysis, nausea, breathing difficulties and possible death.
Jellyfish have an intricate stinging technique. It uses a nematocyst discharge method of stinging. A nematocyst develops in a capsule in the cnidocyte. When the covering of this nematocyst is disturbed, the nematocyst is released. This is caused by a large influx of water pressure that forces it out. The nematocyst has little hooks/barbs on it that help it attach to the prey. Once this has happened the toxins enter the prey and being to take their effect. Sever burns along with numbing of the body and even death can be the effects of this toxin.
The discovery of the “mimic octopus” is just another example of an amazing animal that lives in our beautiful ocean. Preservation of our coral reefs and vast oceans is of utmost importance. The reef is a very delicate and sensitive ecosystem, home to millions of animals all around the world. We must take it upon ourselves to help to preserve this natural resource. There is no telling what new and exciting discoveries are out there to be found. Some of these discoveries may help to benefit human kind and others may just help to feed our hungry minds with new and interesting knowledge for years to come.

Bibliography
Croke, Vicki. Mock-to-pus. Popular Science, Jan 2002

Davidson, Osha Gray. The Enchanted Braid: Coming to Terms with Nature on the Coral Reef

Miller, Harley. Zoology 5th edition

Norman, Finn, Tregenza. Dynamic Mimicry in an Indo-Malayan Octopus. The Royal Society 2001.
Norman, Mark. Masters of Mimicry. Nature Australia, Spring 2002, Vol 27 Issue 6

Roach, John. Newfound Octopus Impersonates Fish, Snakes. National Geographic.


Young, Emma. Magnificent Mimic Reveals Multiple Impressions. New Scientist.com


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