The Dark Line on Shrimp: What It Is and When to Remove It
You have seen it a hundred times. You are peeling shrimp for dinner and there it is: that thin, dark line running along the back. Maybe you dutifully…
What the Dark Line Really Is
Start with the most common misconception: it is not a vein at all. That dark line running along the back of a shrimp is the digestive tract, essentially the shrimp’s intestine. The dark color comes from undigested food and waste, usually algae, plankton, or whatever the shrimp was feeding on before it was caught.
Shrimp have what is called an open circulatory system, which means their fluids are not carried through veins the way ours are. So there are no blood vessels running along that line. There is also a faint white line along the underside of the shrimp, and that one is the nerve cord, the shrimp’s equivalent of a spinal cord. Most people never notice it, and it is completely harmless.