Acanthopotamon martensi ( Wood-Mason, 1875 )

Acanthopotamon martensi ( Wood-Mason, 1875) View in CoL

( Fig. 1 View Figure 1 )

Paratelphusa martensi Wood-Mason, 1875: 230 .

Paratelphusa martensi — Wood-Mason, 1876: 122 (list). — Henderson, 1893: 386.

Parathelphusa martensi — de Man, 1898: 438 (list).

Potamon (Parathelphusa) martensi — Rathbun,1905: 258.

Potamon (Acanthotelphusa) martensi — Alcock, 1910: 68. — Ramakrishna, 1951: 92.

Potamon (Spinopotamon) martensi — Bott, 1966: 476.

Acanthopotamon martensi View in CoL — Bott, 1970: 145. — Deb, 1998b: 382. — Yeo and Ng, 2007: 275 (list). — Ng et al., 2008: 159 (list). — Rahman et al., 2008: 13. — Ng et al., 2011: 60 (list). — Nesemann et al., 2013: 218 (list). — Klaus et al., 2017: 567. — Pati and Thackeray, 2018: 9 (list). — Pati et al., 2019: 451 (list).

Material examined. 2 males (29.97 × 24.13 mm, 26.34 × 19.43 mm), 2 females (23.94 × 19.45 mm, 23.24 × 18.99 mm), ZSI-WRC C.1920, India, Odisha State, Jagatsinghpur District, Banikunda , 20.332 86.155, altitude 12 m, 23 July 2017, S. R. Mohanty coll. GoogleMaps ; 5 males (22.58 × 17.90 mm, 22.35 × 18.43 mm, 22.34 × 18.18 mm, 21.50 × 17.64 mm, 20.15 × 16.65 mm), ZSI-WRC C.1921, same data as preceding collection .

Comparative material. Syntype male (29.2 × 22.0 mm), ZSIK 4069 /4, India, Bihar State, Purnia District, Purnia (= Purneah) [~ 25.780 87.470], altitude ~ 42 m, no date, museum collector GoogleMaps .

Diagnosis. Carapace subhexagonal, relatively broad ( CW /CL = 1.3–1.4); anterolateral margins each with 3 prominent epibranchial teeth; first epibranchial tooth distinctly broader than second- and third epibranchial teeth, directed anteriorly, basally broad, tip acute, separated from external orbital tooth by distinct cleft; second epibranchial tooth directed laterally, basally narrow, tip acute; third epibranchial tooth directed laterally, basally broad, tip acute; posterolateral margins almost straight, converging; postorbital cristae relatively long, extending beyond level of mid supraorbital margin; external orbital tooth broadly triangular ( Fig.1A View Figure 1 ). Major cheliped carpus with well-developed, acute inner distal tooth ( Fig. 1A View Figure 1 ). G1 with flexible zone strongly reduced; terminal segment relatively stout, subcylindrical, relatively long, approximately 0.4times length of subterminal segment; subterminal segment with inner (mesial) margin straight just below flexible zone, outer (lateral) margin sharply raised in proximal half to distinct shelf or hump ( Fig. 1B–D View Figure 1 ). G2 longer than G1, approximately 1.1–1.2 times length of G1; distal segment relatively short, approximately 0.5 times length of basal segment ( Fig. 1E View Figure 1 ).

Ecological notes. Specimens of A. martensi were collected from shallow burrows (<0.3 m deep) along the margins of a turbid water channel adjacent to rice and sugarcane fields ( Fig. 2 View Figure 2 ). The margins of the water channel have a profuse growth of Kans Grass ( Saccharum spontaneum L. of the family Poaceae ). At the collection site, these crabs are very common and active during the rainy season (July-September) only.

Geographical distribution. Acanthopotamon martensi has a wider distribution in the northern part of the Indian subcontinent, with confirmed records from Bangladesh, India (Bihar, Haryana, Punjab, Uttar Pradesh, Uttarakhand, and West Bengal States), Nepal, and Pakistan (see Pati et al., 2019) ( Fig. 3 View Figure 3 ). Until now, the distribution of A. martensi was limited to the ‘Ganges Delta and Plain’ and the ‘Lower and Middle Indus’ freshwater ecoregions ( Fig. 3 View Figure 3 ) ( Abell et al., 2008; Pati et al., 2019). The present record of A. martensi from Odisha confirms its occurrence in the ‘Northern Deccan Plateau’ freshwater ecoregion ( Fig. 3 View Figure 3 ) ( Abell et al., 2008).

Remarks. According to Shih et al. (2009), potamid crabs are not known from the main Indian subcontinent south of the Ganges River. They also noted that strong competition from the dominating gecarcinucid crabs in the Indian Peninsula may have restricted the southward extension of potamids. The present record of A. martensi from Odisha, however, represents the southernmost record of the family Potamidae in the Indian subcontinent. In fact, A. martensi is one of two potamid species that is known from the south of the Ganges, the other species being Acanthopotamon panningi ( Bott, 1966) ( Fig. 3 View Figure 3 ; see Bott, 1966; Pati et al., 2019: fig. 1).

Counting the present record of A. martensi , five species of freshwater crabs are now known from Odisha State. Odisha possesses four major physiographic regions: 1) Eastern Coastal Plains, mainly formed by the deltas of six major rivers; 2) Northern Plateau, an extension of Chota Nagpur Plateau; 3) the Central Tract, consisting of plateaus, hills, uplands and valleys; and 4)Eastern Ghats( Tikader and Chhotani, 1987). All these regions provide an array of habitats for freshwater crabs.Most of these regions, however, have been underexplored for freshwater crabs. The present new record of A. martensi and the description of a new species by Pati and Sharma (2012) indicate that there may be more freshwater crab taxa yet to be recognized from the state. More systematic surveys on freshwater crabs, therefore, need to be conducted in Odisha.