· It’s the intestine: The dark line running along the back is the shrimp’s gut, which can contain sand, algae, plankton, or undigested food.
· Sometimes it looks red: In larger shrimp, a reddish line might be the hepatopancreas (a digestive gland), but the usual dark “vein” is the intestine.
· Is it harmful? No. Eating the vein is not dangerous; cooked shrimp with the vein left in is perfectly safe.
