ink sac

noun

1. a large gland in most cephalopods, as the cuttlefish, octopus, and squid, that is near the rectum and ejects ink at predators.
2. a flexible structure containing ink.

Example Sentences

The well-preserved fossil also “shows some evidence of an ink sac,” probably used to squirt out a dark liquid cloak to help to evade predators, just like modern octopuses, said Christopher Whalen, an American Museum of Natural History paleontologist and co-author of the study published Tuesday in the journal Nature Communications.

From Washington Post

It is preserved well enough that its ink sac and fins are readily visible, as is the very sharp-looking tooth stuck just below its head.

From New York Times

Each one contained a preserved ink sac.

From Scientific American

The fossilized ink sac of an ancient cephalopod—the group of tentacled invertebrates that includes today’s octopi, squid, and cuttlefish—still holds some of the ink pigment, a new study suggests.

From Science Magazine

Again, do not puncture the digestive gland or ink sac during this process.

From Scientific American