A2Ms have been discovered in penaeid shrimps, such as, P. monodon [131], L. vannamei [132], F. chinensis [133] and F. paulensis [134]. The different A2Ms have different orders of multimerization but in case of shrimp, they are homodimers. Immunogold labeling of A2M in the hemocytes of F. paulensis indicated that it was stored in the vesicles of the shrimp granular hemocytes [134]. Interestingly, the shrimp A2M expression level is altered upon bacterial, viral and fungal infections at either the transcriptional or the translational levels [39,131,133e135] revealing its likely diverse functions in shrimp immunity.