Sexual dimorphism of the olfactory system is common in crustaceans; however, it has never been confirmed empirically to be sex dependent. In the current study, the growth pattern of aesthetasc (i.e., olfactory chemosensors of crustaceans) number in 4 protandric simultaneous hermaphroditic shrimp species in the genus Lysmata with 2 social systems—pair living (Lysmata amboinensis and Lysmata pederseni) and group living (Lysmata boggessi and Lysmata wurdemanni)—from male phase to euhermaphrodite phase were examined. The results show that the aesthetasc numbers of both male-phase and euhermaphrodite-phase shrimp are related in general to timing of sex change; in other words, those shrimp that change sex later have greater aesthetasc numbers than those that change sex earlier. This factor is the major reason contributing to the high variation in aesthetasc numbers in euhermaphrodite-phase shrimp. The aesthetasc number increased with shrimp growth during the male phase, but thereafter male-phase shrimp change into euhermaphrodite-phase shrimp and the aesthetasc number increased slowly at first and then stabilized, and even decreased in some. Our results suggest explicitly that the aesthetasc number in Lysmata shrimp is sex dependent and most likely related to their social environment as well.