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Does an octopus ink?
Yes, an octopus, like every other cephalopod inks. The octopus ink is a dark-colored ink released into the water by most octopus species as an escape mechanism. All octopuses except the Cirrina (deep-sea octopuses) are able to release the ink.
This ink is released from the octopus’ ink sacs which are located between the gills. It is distributed more widely when the release of the ink is accompanied by a jet of water from the siphon. Melanin is the main constituent that gives the ink its dark color. However, slightly different colored inks are produced by each species of cephalopod. The octopus produces black ink, the ink of the cuttlefish is a shade of brown whereas, the squid ink is blue-black.
Why does an octopus ink?
An octopus ink when trying to escape a predator. Once they have been seen by a predator, they can create a distraction with an ink cloud. This ink is ejected from their ink sac and is said to reduce the efficiency of the predator’s olfactory organs. Thus, helping them escape from their predators especially predators that use smell for hunting. Also, the ink clouds of some octopus species act as pseudomorphs or decoys that distracts the predator. Making the predator attack the ink cloud instead of the octopus. Also, octopuses have been seen squirting ink at snails or crabs that approach their eggs.
There are two distinct escape strategies associated with inking in octopus:
- Releasing a large amount of ink into the water: In order to escape, an octopus might release a large amount of ink into the water. It does this to form a dark, diffuse cloud that distorts the predator’s view. This allows the octopus to make a rapid retreat and jet away.
- Releasing a smaller amount of ink with a greater mucus content: When in contact with a predator, the octopus releases smaller clouds of ink that contain a greater mucus content. Thus, forming pseudomorphs, the mucus allows the ink to hold its shape for long. The octopus usually releases these pseudomorphs slightly away from itself and changes color as well. These pseudomorphs released by octopuses almost have the same volume and looks that are similar to the octopuses that released them. As a result, many predators have been seen mistakenly attacking these pseudomorphs instead. Thereby, allowing the octopus to escape. However, this behavior is usually referred to as the blanch-ink-jet manoeuvre.
Octopus ink sac
The ink sac is an anatomical feature that is seen in many cephalopod mollusks as well as octopuses. It is the organ that produces the defensive ink they squirt. Octopuses possess an ink sac which is found under the digestive gland.
However, attached to this sac is a gland that produces the ink. The sac then stores the ink. Usually, the ink passes through the glands before it leaves the siphon (the funnel). The ink is then mixed with mucus by these glands. Thus, it forms a thick dark blob that enables octopuses to escape their predator.
An octopus ink sac is close to the siphon. This arrangement is structured in such a way that with a water jet, the octopus can shoot out the ink. Melanin is the main pigment that makes up the ink. This melanin gives it its black color. However, some octopus species lack the ink sac e.g the Cirrate octopuses.
This ink sac is a muscular bag that forms as an extension of the hindgut. The ink sac is a modified hypobranchial gland that lies beneath the gut and opens into the anus. However, its nearness to the base of the funnel means that as the animal uses jet propulsion, the ink can be distributed by ejected water. This ejected cloud of melanin is held together by mucus particles. Thus, it forms a lump that is approximately the size and shape of the octopus. As the predator fixes its attention on the ink, these octopuses make a swift escape.
What is the octopus ink made of?
The main constituent that makes up an octopus ink is melanin and mucus. Depending on the species, the inks in cephalopods contain a lot of chemicals in a variety of several concentrations. The ink can also contain the following:
- Small amounts of free amino acids
- Aspartic acid
- Glutamic acid
Types of ink shapes
The shapes taken by ink when released can be grouped into 6 types:
- Diffuse puffs
- Pseudomorph series
- Ink ropes
- Clouds or smokescreens
- Mantle fills
Is octopus ink poisonous?
Contrary to popular belief, the ink from an octopus is not entirely toxic. However, there are some upcoming studies that have shown that cephalopod ink is toxic to some cells and tumor cells. Though this research is still ongoing and under investigation. Currently, it remains unclear if the octopus ink is truly poisonous via oral consumption. However, it may not be that poisonous as it has made its way into some culture’s cuisines.
For instance, octopus ink has been used by humans in cooking. This is done mainly in Japan and the Mediterranean. It is used in pasta and sauces as a food coloring ingredient and for flavorings. Also, in the past, octopus ink was used for pens and quills.
Furthermore, many animals that prey on cephalopods have advanced chemosensory systems. Some evidence suggests that the irritation, numbness, or even deactivation of such chemosensory systems can be caused by compounds like tyrosinase that are present in the octopus ink. However, few controlled experiments have been carried out to substantiate this. The ink of cephalopods is thereby thought to be more sophisticated than being just a simple smokescreen.
Octopuses as well as squid and cuttlefish like to make a dramatic exit. They generate ink to confuse and deter predators. This ink is ejected from a structure in their body referred to as the ink sac. The ink is mixed with mucus before being released into the water.
These released ink can take on several forms such as the classic ink cloud, worm-like trails, diffuse puffs, pseudomorphs, pseudomorph series, ink ropes, clouds or smokescreens, and mantle fills. The pseudomorphs are ink streams that resemble the octopus releasing them. It is used to distract a predator from pursuing the octopus. The other forms listed could also serve as a distraction or for concealment. Thus, allowing the octopus to escape.
There are experiments that show that some fish are deterred by ink. This is probably due to the chemical composition of the ink. The octopus ink contains melanin, cadmium, lead, copper, and polymers that might have anti-cancer properties. It has also been discovered by researchers that the release of ink by one or more individuals can alert other cephalopods to nearby threats. Thus, making them jet away or adopt defensive behaviors to avoid being eaten by their predator.
Jamar holds an M.D. from Yale University as well as a B.S. in Biology from Brandeis University. He currently conducts research in the field of Microbiology with a specialized focus on bacteria. Outside of work Jamar enjoys spending time with his family and writing about his field of study to help students and other industry professionals better understand its effects on the world.