First record of the coastal water swimming crab from the Indian Ocean

Phylum: Arthropoda

Class: Malacostraca Latreille, 1802

Order: Decapoda Latreille, 1802

Family: Portunidae Rafinesque, 1815

Monomia rubromarginatus (Lanchester, 1900)

Collection: Andaman Sea, east off Little Andaman Island – 10.72°N, 92.71°E, 53 m, 10.08.2019 (FORVSS 388 St. 06), Chain dredge

Voucher No.: CMLRE IO/SS/ANO/00207

Description: Small portunid crab possessing hexagonal carapace, dorsal surface convex, granular patches on protogastric, mesogastric metagastric, epibranchial, cardiac, post-cardiac and mesobranchial regions separated by dense setation; frontal margin with 4 teeth, medians triangular, smaller than and separated from laterals by wide notch; anterolateral teeth 9, anterior eight acutely triangular with convex posterior margins, last laterally directed, 3 times longer than others; posterolateral angle rounded. Basal antennal segment broad, filling orbital hiatus. Mxp3 merus anterolateral angle slightly extended and rounded. Cheliped length 2.0 times CL, merus anterior margin with 3 spines, posterior margin with 1 distal spine; propodus dorsal surface with 2 granular costae, inner costa ending in spine, outer surface with 3 granular costae, spine at carpal articulation; fingers longer than palm. P5 merus posterodistal margin serrate, propodus posterior margin smooth. Male pleon T-shaped, somite 3 with transverse ridge, somite 6 lateral margins subparallel along proximal half, gently converging along distal half, telson elongate triangular, distal margin rounded.

Biological association: None.

Remarks: First record of Monomia rubromarginatus (Lanchester, 1900) from Indian EEZ.

Distribution: Singapore (type locality), Hong Kong, Malaysia, Philippines, Australia, Andaman Sea. Depth range: 6–53 m.

Distribution map:

Identified by: Vinay Padate

Publication: Cubelio S.S., Vishnu K.V., Subi S., Ameri S., Padate V.P., Takeda M. (2023) Morphological and molecular systematics of swimming crabs (Decapoda: Brachyura: Portunidae) from India collected on-board the FORV Sagar Sampada (cruise no. 378, 385 and 392), with notes on biogeography of the Indian portunid fauna. Regional Studies in Marine Science, 62: 102879.

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