Squid can not only be incredibly colorful, as this picture shows dramatically, but they can also change color to blend in with their surroundings. How do they do that ?
Why Squid Change ColorSquid skin is translucent. Color comes from pigment cells, called chromatophores, located in the outer layer of skin. These chromatophores appear as small patches or dots. Chromatophores in California market squid contain red, yellow, or brownish-black pigments.
Model of the Sepioteuthis Chromatophore
After N Caloylanis and C Berger, Marine Biological Laboratory, Woods Hole, MA 02543
Judging Squid Freshness by ColorThe bright colors of live squid, fade after the squid is harvested, as this sequence shows.
30 seconds after harvest
California squid are harvested with round-haul nets and pumped from the sea across a dewatering screen and into a hold containing refrigerated seawater. In this photograph, the squid are less than 30 seconds out of the water. These squid exhibit the natural color variation seen in freshly harvested California squid.
5 minutes after harvest
Squid die quickly after harvest. These squid were photographed minutes after harvest, and illustrate the natural color variation present in California squid. After death, squid coloration slowly fades, but the colors do not change.
1 day after harvest
When squid are unloaded from fishing vessels, they are immediately transferred into bins containing ice water. Squid are soaked in ice water for a few hours until they are processed. These squid, photographed 24 hours after harvest, show the bleaching effect of the ice water, but also show that squid retain some of the natural color they had when harvested.
3 days after harvest
California squid held at 4 ° C (40 ° F) for 3 days after harvest retain some of their natural color and continue to show some color variation. The top (dorsal) view of the squid appears brownish in color, the ventral view (underside of squid) is reddish in color. When the skin is removed (bottom picture), the squid meat appears nearly white, without discoloration.
6 days after harvest
California squid held at 4 ° C (40 ° F) for 6 days after harvest retained some natural color variation. The squid meat still appeared white, although a slight off-color odor was present due to enzymatic breakdown of the squid viscera and muscle.
10 days after harvest
California squid held at 4 ° C (40 ° F) for 10 days after harvest retained some natural color variation, but the skin appeared slightly reddish-purple in color. The meat of the squid was mostly white with some red to purple discoloration. The odor of the squid was strongly putrid.
Poor quality squid have a dark red or purple discoloration of the meat, and a strong off-odor.