The group of mollusks that includes octopuses, cuttlefish, squids, ammonites, nautiluses and belemnites, are not only strange when anatomically compared to their shelled relatives like bivalves, snails and chitons, but their evolution, physiology and behavior makes them almost as interesting as vertebrates. Generally, black ink is produced by octopuses, blue-black ink comes from squid and cuttlefish produce ink that is a shade of brown. The ability to squirt ink and create a smokescreen is a defense mechanism and these inky adventures usually occur just before they jet off to safety.
The ink is mostly made from a dark pigment called melanin, which is suspended in thick mucus along with small amounts of other things such as amino acids. The ink sac is connected to the end of the intestine and feeds into the rectum, controlled by a sphincter and in some inking events mucus from another organ, the funnel organ is ejected with water and ink through the anus and the siphon (a part of their bodies that helps them breathe, feed and move, the funnel that the squid uses for jet propulsion) to create a cloud of ink. When a squid wants to “ink”, it squeezes the sac so that the ink squirts into the siphon. There, it mixes with water and is forced out as the squid shoots off in the opposite direction. If they feel under attack, they will shoot out the ink creating dark, thick clouds of pigment in the water, masking their quick departure, so the predator will not be able to see clearly and then the squids will swim away and escape the predator.
Written for July Writing Prompts – Inky adventures.