Hmmm... Why do you want to work with that gene? there is something special on it? I'm sorry I don't know (even I checked a mexican book about crustaceans, in the appendix appear the genes used in crustaceans and its not there, I think its not recorded to Mexico) any work with that gene.
Maybe if you give us more information, about what do you want to do or with what decapod specifically you are working with.
There is differencies in protein profil (among species) when exposed in the same concentration. I do not know what kind of protein (not yet characterized) but think may there is (are) defferencies in metalothionein gene.
That is already used for some decapod crustaceans and its the most consistent MT primer used (or that I know).
That ones (primers) appeared in a paper (Metallothionein genes from hydrothermal crabs (Bythograeidae, Decapoda): Characterization, sequence analysis, gene expression and comparison with coastal crabs, Leignel, V., 2008) and there is another ones, maybe you can check them.