In large prawns are there 2 veins, which are to be deveined?

Question

In large prawns, I sometimes get to see a thin black colored thread in the prawn even when it's mentioned that it's deveined. I've seen this is good restaurants and also in the frozen food packs. So, that thread something else or is it a vein?

Answer 1

The thick gray/black "vein" that is removed from shrimps and prawns is actually the digestive canal. The thin thread you sometimes see is an artery that runs down the length of the body (ironically, it has more in common with a vein than the thing we call "the vein"). While you could remove it, it's thin and delicate and connected to the flesh by smaller branching blood vessels, so it would tend to come apart and be a lot of work to remove comprehensively.