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.

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.

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.
To install a new ink sac, gently scrape old glue and pieces of ink sac off the end of the section.
6 mm possesses an incipient light organ located in the center of the ventral surface of the ink sac (Fig.
A medial portion of the ink sac, extending from the posterior end, covers much of the center ventral surface of the organ, and diverticula of the ink sac have moved in from the lateral margins, covering the lateral central portion of each lobe.
To study the mode of infection following hatching, the region near the ink sac and gut tissues was observed in newly hatched juveniles.
For instance, if a pen has a lever fill but has not been used for a long time, the ink sac will undoubtedly have solidified and need replacing.
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.
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.