Morphological and molecular characterization of the thunder crab Myomenippe hardwickii Gray, 1831 (Brachyura: Menippidae) from the Malabar coast, India

The thunder crab, Myomenippe hardwickii, has been reported to be seen across Southeast Asia, including the Indian coast. However, previous research has lacked detailed taxonomic descriptions, color photographs, or the molecular characterization of Indian specimens. This study presents the first comprehensive documentation of M. hardwickii in India, combining both morphological and molecular taxonomy techniques. It also represents the first recorded occurrence of this species along the Malabar Coast. DNA barcoding was performed using mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) gene markers to validate the species identity based on taxonomic classification. Previous taxonomic references indicate that the gonopods of M. hardwickii and its sister species, Myomenippe fornasinii Bianconi, 1851 are similar. However, this study marks the first instance of presenting a detailed description and illustration of the male gonopods (G1 & G2) and outlining the characteristics of the vulvae in female individuals of M. hardwickii. Consequently, we have provided species identification supported by appropriate illustrations and ecological information.