Sepia Apama-giant australian cuttlefish

sepia apama - The Giant Australian Cuttlefish

Picture from http://www.daveharasti.com/nelsonbay/cephlapods/sepia_apama.jpg

http://www.youtube.com/watch?v=FcRTc8IWHpM

The Sepia apama has many unique traits that separate it from the almost every other form of mollusk. These features vary from subtle to stunning in their spectrum. Cuttlefish have a highly developed central nervous system and well developed complex eyes. It is the world's largest cuttlefish species, growing to 50 cm in mantle length and over 10.5 kg in weight.

Classification

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Order: Sepiida

Family: Sepiidae

Genus: Sepia

Subgenus: Sepia

Species: apama

Anatomy

http://www.utmb.edu/nrcc/UFAW%20cuttle.jpg

cuttlebone

http://www.susanscott.net/OceanWatch2007/images/cuttlebones3.jpg

In the centre of the Sepia apama there is a structure called the cuttlebone. The cuttlebone is porous and very hard. It is composed mainly of aragonite and is used to control buoyancy. Because of the large cuttlebone, cuttlefish are less active and spend most of their life lying on or hovering slightly above the bottom. Both jet and fins are used, the latter more frequently. Depending on the species, cuttlebones implode at a depth of between 200 and 600 m. Because of this limitation, most species of cuttlefish live on the seafloor in shallow water, usually on the continental shelf. Cuttlebones have both gas-filled forward chambers and water-filled rear chambers.

Blood and Circulation

The blood of a cuttlefish is green because instead of having red hemoglobin, it has hemocyanin, which is a copper-containing protein that helps move oxygen around their body. This is unusual because we have the iron-based hemoglobin. Another unusual feature of the Sepia apama circulatory system is that it has three hearts. Two of these hearts are used to pump blood to the gills, which filter oxygen out of seawater and deliver that oxygen to the bloodstream. The third pumps blood to the rest of the body. However, this unique system has its downfalls. Hemocyanin is substantially less capable of carrying oxygen than hemoglobin and therefore the circulatory system has to work much harder to pump blood. The average lifespan for a Sepia apama is 18 months, this is because their triple-hearted circulatory system uses so much energy, that the whole system just wears out after 18 months.

http://www.mlssa.asn.au/journals/2007Journal_files/image018.jpg

Arms and Tentacles

Although the Sepia apama is classified as ten-arm cephalopods, they really have 8 arms and 2 tentacles. The difference between an arm and a tentacle in cephalopods is that arms have suckers all along them, while tentacles are longer than arms and usually only have suckers on their tips. Sepia apamanormally keep their long tentacles hidden behind their arms. When potential food sources pass nearby, the cuttlefish waves its arms in a mesmerizing display. This attracts potential prey to within grasp of the cuttlefish's tentacles. It then shoots them rapidly to grab the prey. The arms are also important for a defensive exhibit in which the cuttlefish sucks water into its mantle cavity and spreads its arms in order to appear larger to its possible opponent.

Beak

Under the mass of arms and tentacles, the Sepia apama has one other bone in its body, other than the cuttlebone of course. This is the beak of the Sepia apama uses to gnash and bite its prey with. The beak is made of chitin and proteins and is held within a buccal mass. This is a mass of tissue and muscles that act to give the beak a very nasty bite. The beak can be swiveled around at many angles, can project and withdraw, and the whole mass can be dissected out and still function to a high degree. In at least some species, the isolated buccal mass will continue to gnaw away for up to two hours after it's removed. The beak has a distinctive pattern and shape on it depending on the species. This means that scientists can identify which species of cuttlefish have lived and died in certain areas.

http://www.abc.net.au/nature/australasia/img/ep3/gall6.jpg

Lateral Line Analogs

The Sepia apama has a very interesting feature called lateral line analogs. Lateral line analogs compose a mechano-receptive system that assists the Sepia apama in identifying movement in its local area by detecting frequencies. It is a flow-sensing organ.

Ink

The Sepia apama, like many other cephalopods squirts ink through an ink sac. The ink sac is located between the gills and secretes an ink made mostly of melanin and mucus. The function of the ink for the evasion of predators; if the Sepia apama feels threatened; it will shoot the ink from its body and will swim to safety. The Sepia apama can choose whether to spurt ink in the form of mucus, or in the form of a giant cloud.

Brain, Movement, Mantle, and Respiration

The brain in the Sepia apama is known to be one of the largest in brain-to-body ratio of any invertebrate. In some studies it has been more reliably intelligent than the octopus. Although the Sepia apama uses its mantle cavity for jet propulsion, it mainly uses fins that encircle its body to move. With these fins, the Sepia apama can move in any direction. For travel with jet propulsion, the Sepia apama sucks water into the mantle by expanding it and then uses very powerful muscles to shoot water out of an opening in the mantle that propels the Sepia apama forward. The mantle is also responsible for respiration in the Sepia apama, by pumping water into its gills.

Eyes

http://farm1.static.flickr.com/80/234488140_7d5bc3ebf0_o.jpg

The cuttlefish have some of the most well developed eyes in the animal kingdom. Although most kinds of cuttlefish have “W” shaped eyes, the Sepia apama have a bent horizontal slit. Sepia apama are color-blind, they are excellent at detecting low levels of light and can even detect polarized light. While humans focus our eyes by changing the shape of our lens, the Sepia apama changes the shape of its entire eye! The Sepia apama has a higher level of visual acuity than a cat. If the Sepia apama wants to focus on an object, it will contract the muscles around it eye and push its lens forward and away from the retina. To focus on things that are far away, the Sepia apama does the opposite and relaxes those muscles.

Skin

Perhaps the most interesting, mysterious, and miraculous of all of the Sepia apama traits is its innate ability to blend in with its surroundings with the natural ability to change the colour and texture of its skin within seconds. The cuttlefish is known as the chameleon of the sea. The cuttlefish has the best camouflage system in the world. The Sepia apama has a dense layer of pigment cells under its skin called chromatophores. Chromatophores are yellow, red, orange, and dark brown to black, with a density of about 30,000 per square inch. Chromatophores contain pigment as well as two kinds of reflectors called iridophores and leucophores. When certain muscles contract or relax, the appearance color of the cells change. These cells are responsible for the Sepia apama talent. These cells are controlled by papillae muscles, which also control the ability to change skin texture. The Sepia apama can change its skin texture from flat and smooth to that of brain choral or sand. Iridophores (also known as guanophores) are made very thin layers of chitin, crystalline chemochromes made from guanine, and reflectin with layers of cytoplasm that diffract light, this reflects shimmering blues, greens, and silvers. Leucophores are flat, branched cells that, like sequins, reflect all colors.

http://www.youtube.com/watch?v=2x-8v1mxpR0

Communication and mating

Sepia apama are mildly social creatures and mainly use their skin to communicate. They reproduce sexually. The Sepia apama skin is used for hunting, defense, deception, and communication. When not blending into their surroundings, the Sepia apama is able to produce a light show like no other in nature. The Sepia apama congregate in the thousands during the winter months in the southern coast of Australia to mate. Although the population of Sepia apama is 1:1 at birth, during the mating season the ratio becomes 11:1 in favor of the males.. The male find the best spot they can for and egg chamber, the bigger males get the better egg chambers. Therefore the females look for the biggest males when mating. The males create a series of patterns on their skins as well to attract females. These patterns move along theSepia apama skin in a mesmerizing sequence. A trick that some of the other Sepia apama use to get mates is they make the side facing a female look like their a female so that they can get close enough to the real female to mate with it and look like a male on the other side of their body to repel other males. Cuttlefish mate head-to-head, the male places its gentic material into a pouch beneath the females mouth. In a single day one female was documented to mate 17 times, with 8 different males, and lay 37 eggs in the course of 9 hours. Females attach their eggs individually to the underside of rocks, ledges, and caves in subtidal rocky reef habitats, and the eggs hatch in 3–5 months.

http://www.youtube.com/watch?v=fR7Dqf0vzzQ

Habitat

Sepia apama is native to the coast of Australia, from Brisbane in Queensland to Shark Bay in Western Australia. It occurs on rocky reefs, seagrass beds, and sand and mud seafloor to a depth of 100 m.

http://farm1.static.flickr.com/149/339518520_3672695712.jpg?v=0

Food (In and out)

Sepia apama mainly eat crustaceans and small fish (i.e. shrimp). They often change their skin to look like seaweed and wave their tentacles in order to entrance their victims. With a lightening fast motion, they shoot out tentacles that grab prey and bring them back to their beak. There, the animal is eaten. Sepia apama are primarily diurnal. The Sepia apama are also prey to many animals, including fur seals, sea lions, albatross, dolphins and sharks. After the Sepia apama digests its prey, the undigested materials are compressed and packaged, then discharged through the anus into the mantle cavity and are carried away from the animals in the water currents. This packaging of wastes in solid form prevents the excrement from contaminating the water and re-entering the cuttlefish through its gills.  Excretory functions are carried out by a pair of nephridia, tubular structures that collect fluids from the coelom and exchange salts and other substances with body tissues as the fluid passes along the tubules for excretion. The nephridia empty into the mantle cavity.

Fun Facts! (cuttlefish in general, not necessarily sepia apama)

Cuttlefish blood is said to be the ancient dye used by Jews in teckhelet. The recipe for the dye was lost for thousands of years and has recently resurfaced.

Christian groups often use the cuttlefish as an argument towards creationism. They argue that there are too many coincidences and that the cuttlefish could not have survived if it had developed through evolution.

You may be wondering where this mollusks outer shell went. It went from an outer shell to an inner shell! The cuttlefish’s cuttlebone is its current version of what used to be its outer shell.

The original “India Ink” used in fountain pens before the biro was invented was ink from cuttlefish collected in the Indian Ocean.

Cuttlebones are sold commercially as a beak sharpener and supplementary calcium source for birds.

Bibliography

Norman, M.D. 2000. Cephalopods: A World Guide. ConchBooks.

http://www.britannica.com/EBchecked/topic/103036/cephalopod/35763/Locomotion#ref=ref413527

http://www.pbs.org/wgbh/nova/camo/anat-nf.html

http://www.reefed.edu.au/home/explorer/animals/marine_invertebrates/molluscs/squid,_octopus,_cuttlefish

http://www.newworldencyclopedia.org/entry/Cuttlefish#Circulatory_system_and_locomotion

http://www.weichtiere.at/Mollusks/Kopffuesser/Sepia apama.html

http://pharyngula.org/index/weblog/comments/cephalopod_gnashers/

http://209.85.173.132/search?q=cache:K1TkVnHY_Z0J:www.millersville.edu/~biology/faculty/boalpdfs/7.komak_et_al_mfbp_2005.pdf+lateral+line+analog+cuttlefish&cd=2&hl=en&ct=clnk&gl=ca

http://www.pbs.org/wgbh/nova/camo/boal.html