魚類，蝦, 冷血動物, can they feel pain?

cold-blooded or warm-blooded is not the factor determine whether the animal can feel pain or not.
if they have the pain receptor, they can feel pain

of course they do feel pain..
all animals on earth feel pain.
some ppl said that they can't feel pain because they are just describing some ppl are 冷血..
no matter whom they are, if they are animals ..they have feelings just like we do.