ink sac

Octopus defense organ

An ink sac is the internal organ in cephalopods—squid, octopuses, and cuttlefish—that produces and stores ink.

When threatened, the animal expels dark fluid to create a cloud that confuses predators and allows escape.

The ink was historically harvested to make sepia pigment.

anatomy

cephalopod

Tentacled marine mollusk class

squidTen-armed marine mollusk
octopusEight-limbed sea mollusk
cuttlefishColor-changing cephalopod with internal shell

gland · secretion · siphon · melanin · reservoir · duct · membrane · organ · nautilus · mollusk

pigment

sepia

Reddish-brown pigment

dyePigment for changing hues
melaninNatural coloring compound
colorantSubstance that imparts hue

stain · tincture · hue · shade · umber · brown · writing · calligraphy · artistic · drawing

defense

squirt

Forced liquid jet

ejectThrow out forcibly
cloudAtmospheric water vapor mass
predatorOrganism that consumes others

escape · protection · startle · survival · threat · repel · deterrent · distraction · decoy · smokescreen

Categories

squidtentacles, mantle, fins, beak, eyes
animal defensespoison, venom, toxin, toxins, horns
animal featuresbeaks, scales, antlers, fur, ears
marine anatomytentacle, tentacles, fin, fins, gill
pen partscap, nib, clip, tip, barrel
sacspouch, bladder, vesicle, bursa, cyst

Opposites

anatomical function

ink sacvenom gland

Organ producing toxic secretion

poison gland · stinger · fangs · claws · electric organ

concealment vs. exposure mechanisms

ink saclure

Thing that tempts

Family

ink, inky, inks, inked, sac, inking, inkiness, inkwell, sacs

Familiarity: Top 500,000
Profile: Used worldwide · Timeless · Concrete · Everyday, not technical · Rated G