DM domain genes are a group of transcription factors that are integral to sexual development and its evolution in metazoans. Their functions and regulatory mechanisms are not well understood in Malacostraca (crabs and crayfish) while these sex regulators have been widely identified in the past decade. In this study, the family was investigated in the decapod crab, . We find that most members of the family begin to enrich around the juvenile 1 stage. In reproductive organs, , , and highly express in the male-specific androgenic gland (AG), while , , , and show relatively high expression in testis. Also, we find the highly aberrant expression of and in the chimeric AG, strongly indicating their function in AG development. Moreover, RNA interference of , , and results in a significant decrease in transcription of the (), respectively. Our findings suggest that genes in primarily function in male sexual differentiation, especially in AG development. Besides, this study identifies two unique groups of genes in Malacostraca: and . In Malacostraca , we uncover a cryptic mutation in the eight zinc motif-specific residues, which were firmly believed to be invariant across the family. This mutation sets the Malacostraca apart from all the other genes and implies a different way of transcriptional regulation. Genes from the group show phylogenetical limitation to the malacostracan species and underwent positive selection, suggesting their highly specialized gene function to this class. Based on these findings, we propose that and in Malacostraca have developed unique transcriptional regulation mechanisms to facilitate AG development. We hope that this study would contribute to our understandings of sexual development in Malacostraca and provide new insights into the evolutionary history of the family.