Cuttlefish Cuttlefish, belonging to the class Cephalopoda, are marine mollusks. They have eight arms and two tentacles furnished with denticulated suckers. These tentacles are used to hold prey while the cuttlefish feeds on it using its beak.
The cephalopods possess highly developed nervous systems and relatively large brains compared to other invertebrates. The cuttlefish's brain is divided into large symmetrical halves, one half being concerned with the vision-predominant Octopus vulgaris. They exhibit a range of fascinating behaviors such as fast swimming, jet-propulsion, and more importantly camouflage through rapid color change (metachrosis), which is used to evade predators or prey upon other animals.
A cuttlefish can quickly adapt its coloration and pattern to match its current environment by regulating pigments in the skin cells called chromatophores, which can be expanded and contracted under hormonal control. Chromatophores contain different colors and patterns of pigments, so different species can differ significantly in appearance. The animal can also use specialized skin cells called iridophores and leucophores that reflect light, appear shiny or lustrous to human eyes, or change color during a fight.
Cuttlefish are considered one of the most intelligent invertebrates. They are able to use tools and learn through observation. They have also been found to engage in play behavior, which may or may not be related to sexual gratification. Cuttlefish are used extensively in biological research, especially in neurobiology because their large nervous system is very easy to study both experimentally and by observation.
Cuttlefish are characteristically preyed upon in the wild by sharks, seals, predatory fish such as barracuda and tuna, as well as other cuttlefish. Their ink is used as a purple dye for liqueur and food such as pasta or cheese, as well as chemical weapons against predators, although this is usually a last resort.
Cuttlefish are found in all the world's oceans from the surface to depths of about 1,500 meters. Only some species live in brackish water and those that do travel long distances as part of their lifecycles. It has been suggested that they also migrate vertically using tidal currents as part of their reproductive cycle as well as horizontally as nomadic hunters. Cuttlefish live in burrows on the seafloor and benthic octopuses also occupy these burrows.
Cuttlefish possess eight arms arranged around a beak-like mouth, with which they grasp prey; two longer tentacles they may use to help capture and manipulate prey; and two sensory tentacles, which house the statocysts that enable them to sense their surroundings with balance and precision. Cuttlefish eyes are among the most developed in all invertebrates and rival those of some vertebrates.
They possess a large brain (the size relative to body weight is greater than that in any other invertebrate) and are considered to be highly intelligent. The cuttlefish brain shares several fundamental structures with the vertebrate brain, including a structure homologous to the hippocampus. The sophisticated nervous system enables rapid color changes that can be used for camouflage or signaling to each other, but it also makes them extremely difficult to keep in captivity because they are so sensitive to fluctuations in water quality, which stresses them out.