I don't see why this should be a surprise. The idea that these animals don't feel pain because they don't produce a sound that we can hear is dumb to start off with.http://www.sciencedaily.com/releases/2013/01/130116195336.htm
Jan. 16, 2013 — The food and aquaculture industries should reconsider how they treat live crustaceans such as crabs, prawns and lobsters. That's according to a Queen's University Belfast researcher who has found that crabs are likely to feel pain.
The latest study by Professor Bob Elwood and Barry Magee from Queen's School of Biological Sciences looked at the reactions of common shore crabs to small electrical shocks, and their behaviour after experiencing those shocks. The research has been published in the Journal of Experimental Biology.
Professor Elwood's previous research showed that prawns and hermit crabs respond in a way consistent with pain.
Professor Elwood says that his research highlights the need to investigate how crustaceans used in food industries, such as crabs, prawns and lobsters, are treated. He said: "Billions of crustacean are caught or reared in aquaculture for the food industry. In contrast to mammals, crustaceans are given little or no protection as the presumption is that they cannot experience pain. Our research suggests otherwise. More consideration of the treatment of these animals is needed as a potentially very large problem is being ignored.
"On a philosophical point it is impossible to demonstrate absolutely that an animal experiences pain. However, various criteria have been suggested regarding what we would expect if pain were to be experienced. The research at Queen's has tested those criteria and the data is consistent with the idea of pain. Thus, we conclude that there is a strong probability of pain and the need to consider the welfare of these animals."
Yeah, and it is impossible to demonstrate absolutely that a human experiences pain. We can only experience our own pain.