What if I told you that you can find alien life right here on earth?! Believe it or not you can find it right here in our oceans. An incredible, too amazing too be real creature that has eight arms that grow out of it's head, a W-shaped pupil and a doughnut shaped brain. It has three hearts to pump it's blueish-green blood. A flesh eating predator who can hypnotize it's prey or become completely invisible, and to some people, it is considered a seafood delicacy. This creature is Sepia pharaonis, more simply know as the cuttlefish.
Contrary to it's name the cuttlefish is not actually a fish, rather it is a mollusk.
Evolutionary History and Scientific Classification
Cuttlefish are part of the cephalopod group, and it is believed that the most primitive ancestor of the cuttlefish emerged around 550 million years ago, which may have been in the form of an ancient nautilus-like creature. Speaking from an evolutionary standpoint, fellow cephalopods ,the squid and octopus are the closest cousins to the Cuttlefish.
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Coleoidea
Superorder: Decapodiformes
Order: Sepiida
Phylum: Mollusca
Class: Cephalopoda
Subclass: Coleoidea
Superorder: Decapodiformes
Order: Sepiida
Cuttlefish Habitat and Life Cycle
Cuttlefish Anatomy
Although cuttlefish are mollusks, they do not have a hard shell to protect them from predators, and since they are invertebrates, they do not have any hard bones to make them difficult to eat. Their soft bodies are also high in nutritious protein, making the cuttlefish an easy and nutritious treat for every meat eating sea creature. So how dose the cuttlefish avoid an ocean full of creatures who want to eat them? It's all in their unique skin, which is like nothing else on planet earth.
Cuttlefish Skin and Communication
The skin has an amazing ability to change into a vast variety of different colors, and even texture, to camouflage itself into their natural backgrounds. Their skin is made up of three layers of specialized skin that has up to 200 pigment cells called chromatophores per square millimeter. The first and deepest skin layer is white in color to act as a light retracting base for the other layers. The middle layer produces blue, red, green, orange and even pink through the iridescent light reflecting cells inside the skin. The outer most layer consists of pigment cells that are like tiny disks of color which are too small to see. The layers of specialized skin also contain tiny plates of the protein chitin, called Iridophores, which are responsible for the light reflection. The muscles attached to these pore like disks contract to pull open the disk and allow the color to show through, and when the muscle relaxes, the disk shrinks back and the color disappears. This physiological mechanism is, in a scene, similar to our own eyes, but obviously not in the color changing aspect, rather in the same way that the muscles attached to the iris contract and relax to allow light to pass through.
The cuttlefish also has the ability to completely change the texture of it's skin to aid in it's ability to camouflage so perfectly against it's surroundings. Their skin can go from smooth to bumpy or spiny in a matter of seconds. All of these reactions are caused nerves that send the information signals to the brain. The cuttlefish has truly amazing skin that not only is useful for camouflaging itself from predators, but also is used for communication with other cuttlefish. Scientists are trying to discover and “translate” this secret language, but there are still endless discoveries that have yet to be made in the field of cuttlefish language decoding.
Very little is know about the secret world of cuttlefish communication, but scientists are being to gain a better perspective into the cuttlefish “language.” To predators, a cuttlefish will usually develop two large dark “eye spots” on the top and rear of the head and then use a jet propulsion mechanism that is their cuttlebone to dart of into the distance. To their prey, cuttlefish will splay their arms and put on a hypnotic color display to mesmerize a small fish or crab. If trying to warm another male cuttlefish to back off his mate, the cuttlefish will put on a “zebra stripes” display.
The Cuttlebone
The cuttlebone helps to control buoyancy and keeps the cuttlefish afloat. Cuttlebones have forward chambers that are filled with gas and water filled chambers in the rear. This calcium rich cuttlebone changes in density to allow the the mollusk to control it's positioning in the water. This balance of gas and water filled chambers keep the animal in neutral buoyancy. The cuttlefish allows requires the use of it's mantle and fins for mobility to slide through the water. The cuttlefish will suck water into the mantle cavity and the muscles inside the mantle will force the water with such force that it propels the cuttlefish through the water.
The Tentacles and Arms
Contrary to octopuses, the cuttlefish has eight arms and two extended tentacles. The tentacles are primarily used for grabbing prey and then hands it off to the arms for eating. However, like octopi and squid, the bottom of the cuttlefish's arms and tentacles are also lined with suckers, for catching prey more easily. The cuttlefish will use these arms, along with the color displays, to stupefy and lure in it's prey. First, the cuttlefish will splay out it's arms into intriguing positions, and will put on mesmerizing color displays. The more determined the cuttlefish is to having the shrimp or small crab, which happen to be it's favorite, the more spectacular the performance. The prey is at first cautious, the curiosity will rule out, and the prey is captivated. Then the tentacles will reach out and grab the tiny creature.
The cuttlefish has relatively large eyes compared to the rest of it's body,and a unique “W”-shaped pupil. Although the cuttlefish is one of the most uniquely colorful animal in the world, it is completely color blind, which is why it is truly amazing how they can match their natural background so perfectly. This suggests that the cuttlefish can not rely on the color of their background or by the color of their own skin to tell if they have matched their surroundings. Scientists suggest that the cuttlefish can see in certain shades of green and by polarized light enhancing the contrast of the world around them. While focusing on any particular object, the whole eye is reshaped by moving the lenses, rather then the reshaping of the lens as a focusing mechanism, as it is true with humans.
The Cuttlefish Circulatory System
The cuttlefish has three hearts to pump it's unusual blue-green blood to the rest of it's body. This unusual color is due high copper content of the protein hemocyanin, which acts as the oxygen carrier. Since hemocyanin has a lower carrying capacity for oxygen, then our own hemoglobin,the heart must pump a greater volume of blood, hence the three hearts. Two of the cuttlefish's hearts are used to transport oxygenated blood to the set of gills, one heart per gill in fact. The third heart is used to transport blood to the rest of the body.
The Ink Sac and Beak
The cuttlefish is equipped with an ink sac as a final defense against predators. The ink can be ejected in two different ways. One way is through the ink being released as mucus encased ink bubbles, that are approximately the same size as the cuttlefish. These cuttlefish sized pockets of ink and mucus, act as decoys and will actually trick and confuse the predator, while the cuttlefish slips away. The cuttlefish can also eject ink by producing an ink screen which allows the cuttlefish a chance to escape. The cuttlefish has a beak, made of the protein chitin, that is located on the inside of it's body, at the base of it's arms and tentacles. The cuttlefish's beak looks quite similar to a parrots beak, and it is extremely sharp. It is used for bitting other rival cuttlefish, and tearing at prey.
Cuttlefish have unique mating rituals that involve the males putting on fantastic color displays and intimating body patterns to impress the females. Thousands of cuttlefish will migrate to the breeding grounds once a year where males always outnumber the females, sometimes as much as ten to one. Mating is highly competitive since cuttlefish only live to see one mating season during their lifetime. All of the cuttlefish essentially have the same goal, that is to pass on their genes, and when the color displays and intimidation fails to secure a mate, the male cuttlefish will throw themselves into brutal, violent and strange looking wrestling matches. While all these color displays, attempts at intimidation, and epic fight scenes are transpiring, the small male, who has no chance in a fight, is doing one of the most bizarre advances in the animal kingdom. The small male will dress himself in the colors of a female to effectively sneak pass all the large rival males, and while the other the other males are still fighting and throwing color displays the small, cross-dressing male will mate with the female. Mating occurs when the male and female cuttlefish join their tentacles together, and using a special arm, the male will hand the female a sperm packet. Whether she uses his sperm packet is completely up to the female, and she will continue to mate with several other partners and collect their sperm packets under her tentacles. The males have no influence over whose sperm will fertilize the females eggs.
Cuttlefish are relativity intelligent for mollusks, and Millersville University professor Jean Boal, Ph. D, conducts experiments on cognitive behavior and conditional discrimination learning in cuttlefish. Boal has been working with cuttlefish for about 17 years, but with octopi for about 22 years. To test the relative intelligence of the cuttlefish and their capability to learn, at her lab in Millersville University, Boal created a simple maze in which the cuttlefish had to escape. Once inside the maze, the cuttlefish would have to make a choice, either go left or right, but only one door would lead to the exit. This choice would be made easier with the help of two features that should cue the cuttlefish on which way to go. A piece of plastic seaweed, on either the left or right side, would indicate the way out, where as a brick indicates a blocked door. What Jean found is that cuttlefish are very good at picking the correct door, this demonstrates that the animal can learn two distinct variables and has the capability to remember the information. This level of intelligence may seem simple to us, but for an invertebrate it is very remarkable.
The cuttlefish truly is one of the world's most extraordinary wonders, due to it's ability to almost instantly and perfectly camouflage itself into any natural background, and proving there is alien life...right here on earth.
“We are testing an animal that is very alien. I mean it's as close, perhaps, as we're going to get to studying an animal on another planet. And is that exciting? That's very exciting.”
-Jessie Purdy to PBS Nova special Kings of Camouflage.
WORKS CITED
Brooks, Micheal. “Do You Speak Cuttlefish?.” New Scientist 198.2653 (2008): 28-31. Academic Search Premier. EBSCO. Web. 7 Oct. 2010.
"Cuttlefish, Sepia officinalis at MarineBio.org". MarineBio.org. Web 4 Nov. 2010.
Flores, Graciela. “Squid Secrets.” Natural History 116.1 (2007): 15. Academic Search Premier. EBSCO. Web. 26 Sept. 2010.
Hansford, Dave. Cuttlefish Change Color, Shape-Shift to Elude Predators. National Geographic Society. 6 Aug. 2008. Web. 7 Oct. 2010.
Hogan, Jenny. “The Meaning of a Cuttlefish's Wink.” New Scientist 178.2395 (2003): 19. Academic Search Premier. EBSCO. Web. 26 Sept. 2010.
NOVA. Anatomy of a Cuttlefish. PBS. Mar. 2007. Web. 7 Oct. 2010.
NOVA. Kings of Camouflage. PBS. 3 Apr. 2007. Web Transcript. 7 Oct. 2010.
Wikipedia contributors. "Cuttlefish." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 20 Nov. 2010. Web. 23 Nov. 2010.
PHOTO CREDITS
Anderson, Doug. Cuttlefish. 23 Sept. 2006. Flickr.
Ito, Joi. Mating cuttlefish. 29 Oct. 2010. Flickr.
http://www.flickr.com/photos/joi/5125555199/
Jacinto, Valter. Concha de Choco // Shell of Common Cuttlefish (Sepia officinalis). 25 July. 2008. Flickr. http://www.flickr.com/photos/valter/2716711158/
Ling, Richard. Giant Australian Cuttlefish. 30 May. 2009. Flickr.
http://www.flickr.com/photos/rling/4965181485/
Ling, Richard. Cuttlefish. 26 Nov. 2006. Flickr.
http://www.flickr.com/photos/rling/2294437995/
McCord, Lance. Cuttlefish. 8 Feb. 2009. Flickr.
NeilsPhotography. Flamboyant Cuttlefish Macro. 30 Oct. 2008. Flickr. http://www.flickr.com/photos/neilspicys/3120827177/
Nemo's great uncle. golden cuttlefish. 8 Sept. 2008. Flicker.
Niedilch, Sebastian. L'Aquàrium: Common Cuttlefish. 30 May. 2009. Flickr. http://www.flickr.com/photos/42311564@N00/3577957710/
Smallwood, Jeff. Cuttlefish Eye. 21 June. 2006. Flickr. http://www.flickr.com/photos/jeffsmallwood/234488140/
