Ink Sac

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ink sac

[′iŋk ‚sak]
(invertebrate zoology)
An organ attached to the rectum in many cephalopods which secretes and ejects an inky fluid.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Ink Sac


an organ in most cephalopods, for example, octopuses, cuttlefish, and squids, in which a fluid is formed containing granules of a black pigment of the melanin group.

The ink sac, which serves a protective function, consists of a glandular portion and a reservoir, which opens into the rectum through a duct. Old cells of the glandular portion are gradually destroyed, dissolve in the secretions of the gland, and accumulate in the reservoir. When threatened, the mollusk ejects the contents of the reservoir, creating a dark cloud in the water that serves as a smokescreen to hide the mollusk. The coloring capacity of the inky liquid is unusually high; for example, the cuttlefish can color the water of a tank holding up to 5,500 liters in 5 seconds. A dye, natural sepia, has been obtained from the dried contents of the ink sac treated with potassium hydroxide.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
LIFELIKE DRAWING: Scientists used ink from a fossilized creature's ink sac to draw its likeness.
If the ink sac (the rubber ink reservoir) is still attached, supple, and without obvious perforations, immerse the tip of the pen in a glass of cool water and squeeze the sac a few times to see whether it holds liquid.
A newly hatched juvenile with an average mantle length of 1.6 mm possesses an incipient light organ located in the center of the ventral surface of the ink sac (Fig.
In the adult female squid, the AN gland is adjacent to the ink sac and digestive organs on the ventral side of the mantle cavity [ILLUSTRATION FOR FIGURE 1 OMITTED].
Positioned in the body of the pen so that it compressed a rubber ink sac contained inside, the lever caused ink to be drawn up sufficient for several hours' writing.
An intact ink sac was placed on a sheet of Parafilm, and the ink duct was transected about 5 mm anterior to its emergence from the sac.
Positioned in the body of the pen so that it compressed a rubber ink sac inside, the lever caused ink to be drawn up for several hours' writing.
Throw away the guts but keep the ink sac if you want it (place in a cup, pierce, dilute with a little water then add it to sauces or risotto at the end of cooking.
Octopuses are such intelligent creatures, and these ones are unusual in that they don't have ink sacs like some other octopuses, so they have to use other defensive methods to escape predators."
They are used as a source for a red-brown ink, called sepia, that they produce in their ink sacs and squirt out to avoid predators.
1/2 k squid, skin and ink sacs removed, cut into rings
They used commercially available eumelanin that had been collected from the ink sacs of Sepia officinalis, a squid-like mollusk commonly known as a cuttlefish.