Form and Function

The common cuttlefish (Sepia officinalis) is a highly mobile invertebrate (Ikeda 2009). Because cuttlefish have no shell, they have acquired strong muscles that allow them to travel for long distances and hunt aggressively. The common cuttlefish is a certain type of mollusk that is part of the group called Coleoid Cephalopoda, along with the octopus and squid (Fluckiger et al. 2008). Cuttlefish have some unique characteristics including their skin, nervous system, arms and tentacles, cuttlebone, heart and blood, and eyes.  

SKIN           
Another important characteristic of cephalopods are their body-patterning techniques. They change their body color and pattern by neutrally controlling their color pigments (called chromatophores) so they can blend into their surroundings, stun prey, or even warn off predators (Ikeda 2009). They can also change the physical texture of their skin to match their surroundings (Kelman et al. 2008). This body-patterning technique can also be used as defensive camouflage to hide from predators or intimidate them, and males use it to compete with other males for the female (Ikeda 2009). When a male wants to impress a female, he will often display a zebra-like pattern, like in the picture shown below (NOVA 2007).

NERVOUS SYSTEM
Cephalopods have a highly developed nervous systems. In fact, they have brains the size of some vertebrate brains (Ikeda 2009; NOVA 2007). The nervous system includes a variety of senses including sight, smell, and even sound ( in the form of pressure waves) (NOVA 2007). The nervous system of the coleoid cephalopods is composed of the optic lobes, the nervous system of the arms, and the central brain. The optic lobes and the nervous system of the arms lie outside of the brain capsule. The central brain surrounds the esophagus and lies inside the brain capsule (Ikeda 2009). The brain is composed of several lobes (basal, superior frontal, and vertical), each of which control different types of behavior (Ikeda 2009). Their large brains allow them to recall information and learn (Ikeda 2009).

ARMS AND TENTACLES
The Cuttlefish has eight arms that are used for grasping prey, and two long tentacles that shoot our from internal pockets to capture prey. Cuttlefish also wave their arms in such a way that lures in prey. Males have a modified arm that is used to transfer spermatophores into the buccal area of the female (NOVA 2007).

CUTTLEBONE
The cuttlebone is what makes a cuttlefish a cuttlefish, and it is used like a swim bladder that helps the organism control buoyancy. The cuttlebone is rich in calcium, therefore, once the cuttlefish dies its skeleton is sought after by other organisms for its nutrients (NOVA 2007).                     

HEART AND BLOOD
Cuttlefish have three hearts! Two of these hearts are for pumping blood to the gills, and the other heart circulates the blood around the rest of the body. Want to know something interesting about their blood? It is GREEN! The copper-containing molecule called hemocyanin is responsible for this color, and is present in all cephalopods. The hemocyanin functions a lot like the hemoglobin in humans; It transports oxygen (NOVA 2007).

EYES
Even though cuttlefish are colorblind, they still have incredible eyesite; They can see in all directions. With their "W" shaped pupil, they can see well in low light, and even detect polarized light! Unlike us, the morphology of their eye allows them to increase the magnification of the object they are looking at; All they have to do is alter the shape of their eye (NOVA 2007).

 

If you are wondering about how this awesome invertebrate came to be, visit the life history/reproduction page!

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