Anatomy
Figure 1. Dorsal view of cuttlefish.
Physiology
A defining characteristic of the cuttlefish, the cuttlebone is a porous internal shell that helps both gas-filled forward chambers and water-filled rear chambers. Although it can take hours for the cuttlefish to change its density through its cuttlebone alone, it can control its position in the water with the aid of its specialized fins and mantle. Cuttlefish have two methods of swimming. They can jet propel themselves backwards by sucking water into their body cavity by means of the cuttlebone and then expelling it through a funnel (siphon). This produces a very rapid backward movement, which is usually used for escaping predators as it is requires a great deal of energy. Hovering and normal swimming is achieved by gentle wave-like movements of their side fins.
The common cuttlefish is classified as a mollusk within the class cephalopoda. This group is characterized by the presence of arms surrounding the mouth and an internal or reduced shell. Their behavior and pattern of living makes them more related to finfish than other molluscan shellfish. The cuttlefish is easily identified by its oval, flattened shape and long, narrow fins that from and undulatory margin along each side of the main body or mantle. The head is relatively large in proportion to the body and has a crown composed of eight arms, each equipped with suction cups on their internal face. The arms surround the mouth and also conceal two long tentacles normally contained in pouches. These tentacles are projected and used to seize prey with the aid of suction cups on their flattened ends. The eyes are situated on the sides of the head and have a “W”-shaped pupils. The mantle is heavily pigmented, characterized by a broad, irregular zebra-like striped pattern, more prevalent in males.
Cuttlefish have one of the most highly developed nervous systems among invertebrates. A relatively large brain is housed within a hard cartilaginous skull. The part of the brain which connects to the eyes is particularly highly developed and complex.
Mollusks are characterized by their mantle which is responsible for excreting their shell, a radula, and a foot. Within the Cephalopod class we see a modified radula and foot and a reduced shell.
Characterized by cephalization: centralization of nervous tissue
Spermatophores: packets of sperm
Hectocotylus: specialized arm that holds spermatophores
Closed Circulatory system: Cephalopods differ from other classes of molluscs in that they have a closed circulatory system with hemocyanin as a blood source.
Siphon: used for jet propulsion
Ink Sac: Cuttlefish and other cephalopods have ink sacs in which to story ink. It is used to stun predators as a defense mechanism. Cuttlefish have a brownish ink, what we now call sepia color.
Muscular lateral fins: Aid in swimming through the water in order to use energy in the most efficient way (as opposed to using the cuttlebone for jet propulsion) They allow the cuttlefish to maneuver very well in the water while maintaining constant speeds
Cuttlebone: the defining characteristic of the cuttlefish, the cuttlebone is a porous internal shell that helps both gas-filled forward chambers and water-filled rear chambers control buoyancy and swimming. The cuttlebone is rich in calcium and is often sold in pet stores as a nutritional supplement for birds.
Specialized Radula (beak): The cuttlefish's beak looks much like a parrot's beak, but it is hard to see because it lies buried at the base of its eight arms. The cuttlefish can use its beak to help subdue prey and to defend itself against predators and rivals by biting.
Eyes: Cuttlefish are colorblind but, they have two of the most highly developed eyes in the animal kingdom. They are able to see well in low light and can also detect polarized light, making it an expert at contrast. Humans reshape their lenses in order to focus on specific objects while the cuttlefish moves its lenses by reshaping its entire eye. Also, the cuttlefish's eyes are very large in proportion to its body and are speculated to increase image magnification upon the retina, while the distinct "W"-shaped pupil helps control the intensity of light entering the eye.
Large brain enclosed in a cartilaginous cranium: an effect of cephalizationSkin: cuttlefish skin possesses up to 200 chromatophores (pigment cells) per square millimeter, allowing the animal to pattern itself with a variety of colors. Useful in courtship displays, camouflage and hypnotizing prey.
Skin: bioluminescent skin cells make the cuttlefish a wonder to watch. Sepia officinalis specifically are characterized by their zebra striped skin when not displaying this bioluminescence.
The common cuttlefish is classified as a mollusk within the class cephalopoda. This group is characterized by the presence of arms surrounding the mouth and an internal or reduced shell. Their behavior and pattern of living makes them more related to finfish than other molluscan shellfish. The cuttlefish is easily identified by its oval, flattened shape and long, narrow fins that from and undulatory margin along each side of the main body or mantle. The head is relatively large in proportion to the body and has a crown composed of eight arms, each equipped with suction cups on their internal face. The arms surround the mouth and also conceal two long tentacles normally contained in pouches. These tentacles are projected and used to seize prey with the aid of suction cups on their flattened ends. The eyes are situated on the sides of the head and have a “W”-shaped pupils. The mantle is heavily pigmented, characterized by a broad, irregular zebra-like striped pattern, more prevalent in males.
Cuttlefish have one of the most highly developed nervous systems among invertebrates. A relatively large brain is housed within a hard cartilaginous skull. The part of the brain which connects to the eyes is particularly highly developed and complex.
Mollusks are characterized by their mantle which is responsible for excreting their shell, a radula, and a foot. Within the Cephalopod class we see a modified radula and foot and a reduced shell.
Characterized by cephalization: centralization of nervous tissue
Spermatophores: packets of sperm
Hectocotylus: specialized arm that holds spermatophores
Closed Circulatory system: Cephalopods differ from other classes of molluscs in that they have a closed circulatory system with hemocyanin as a blood source.
Siphon: used for jet propulsion
Ink Sac: Cuttlefish and other cephalopods have ink sacs in which to story ink. It is used to stun predators as a defense mechanism. Cuttlefish have a brownish ink, what we now call sepia color.
Muscular lateral fins: Aid in swimming through the water in order to use energy in the most efficient way (as opposed to using the cuttlebone for jet propulsion) They allow the cuttlefish to maneuver very well in the water while maintaining constant speeds
Cuttlebone: the defining characteristic of the cuttlefish, the cuttlebone is a porous internal shell that helps both gas-filled forward chambers and water-filled rear chambers control buoyancy and swimming. The cuttlebone is rich in calcium and is often sold in pet stores as a nutritional supplement for birds.
Specialized Radula (beak): The cuttlefish's beak looks much like a parrot's beak, but it is hard to see because it lies buried at the base of its eight arms. The cuttlefish can use its beak to help subdue prey and to defend itself against predators and rivals by biting.
Eyes: Cuttlefish are colorblind but, they have two of the most highly developed eyes in the animal kingdom. They are able to see well in low light and can also detect polarized light, making it an expert at contrast. Humans reshape their lenses in order to focus on specific objects while the cuttlefish moves its lenses by reshaping its entire eye. Also, the cuttlefish's eyes are very large in proportion to its body and are speculated to increase image magnification upon the retina, while the distinct "W"-shaped pupil helps control the intensity of light entering the eye.
Large brain enclosed in a cartilaginous cranium: an effect of cephalizationSkin: cuttlefish skin possesses up to 200 chromatophores (pigment cells) per square millimeter, allowing the animal to pattern itself with a variety of colors. Useful in courtship displays, camouflage and hypnotizing prey.
Skin: bioluminescent skin cells make the cuttlefish a wonder to watch. Sepia officinalis specifically are characterized by their zebra striped skin when not displaying this bioluminescence.
Sources
Pechenik JA. 2010. Biology of the Invertebrates. 6th ed. New York, NY. The McGraw Hill Companies; 256-293p
Arkley K, Jacklin MS, Boulter M, Tower J. 1996. The cuttlefish (Sepia officinalis): a guide to its exploitation in UK waters. The Seafish Industry Authority. [Internet]. [cited 2013 May 1]; Report
number SR467. Available from: http://www.seafish.org/media/publications/sr467.pdf
Webber DM, Aitkin JP, O’Dor RK. 2000. Costs of locomotion and vertic dynamics of cephalopods and fish. Chicago Journals: Physiology and Biochemical Zoology. [Internet]. [cited 2013 April
28]; 73(6). Available from: http://www.jstor.org/stable/10.1086/318100#rid_rf2
NOVA: Anatomy of a cuttlefish [Internet]. c2007. St. Paul (MN): PBS: [cited 2013 April 29]. Available from http://www.pbs.org/wgbh/nova/camo/anat-nf.html
Reid, A., P. Jereb, & C.F.E. Roper c2005. Family Sepiidae. In: P. Jereb & C.F.E. Roper, eds. Cephalopods of the world. An annotated and
illustrated catalogue of species known to date. Volume 1. Chambered nautiluses and sepioids (Nautilidae, Sepiidae, Sepiolidae,
Sepiadariidae, Idiosepiidae and Spirulidae) [Internet]. Rome: Food and Agriculture Organization of the United States; [cited 2013 April
29]. Available from http://books.google.com/books?id=QkkjaSA1jKgC&pg=PR6&lpg=PR6&dq=%5E+Reid,+A.,+P.+Jereb,+%26+C.F.E.+Roper+2005.+Family+Sepiidae.+In:+P.+Jereb+%26+C.F.E.+Roper,+eds.+Cephalopods+of+the+world.+An+annotated+and+illustrated+catalogue+of+species+known+to+date.+Volume+1.+Chambered+nautiluses+and+sepioids+(Nautilidae,+Sepiidae,+Sepiolidae,+Sepiadariidae,+Idiosepiidae+and+Spirulidae).+FAO+Species+Catalogue+for+Fishery+Purposes.+No.+4,+Vol.+1.+Rome,+FAO.+pp.+57%E2%80%93152.&source=bl&ots=c8F_gOCxO5&sig=77c3tWdLUi10O2TNx65Ut8e05VY&hl=en&sa=X&ei=C2aFUayHKMS8yAHisoD4Cw&ved=0CDsQ6AEwAg#v=onepage&q=cuttlefish%20&f=false