Acanthopotamon fungosum (Alcock, 1909)

Shashi, Shibly Sadique, Pan, Da, Emu, Nusrath Jahan, Roy, Mishal, Sadek, Md. Abu, Sharifuzzaman, S M & Sun, Hongying, 2023, Two new records and an updated checklist of freshwater crabs (Arthropoda, Malacostraca, Decapoda, Potamidae and Gecarcinucidae) from Bangladesh, ZooKeys 1167, pp. 211-222 : 211

Acanthopotamon fungosum (Alcock, 1909)

Figs 2 , 4a, b

Potamon (Paratelphusa) fungosum Alcock, 1909: 250.

Potamon (Acanthopotamon) fungosum - Alcock 1910: 65, fig. 12.

Lobothelphusa fungosa - Bott 1970: 148, pl. 38 fig. 25, pl. 46 fig. 23.

Paratelphusa fungosum - Brandis and Sharma 2005: 14.

Acanthopotamon fungosum - Yeo and Ng 2007: 274; Ng et al. 2008: 159.

Material examined.

1 male, 28.84 × 24.28 mm (Table 1 ), Chittagong University Campus , Chattogram, Bangladesh, 22°28'07"N, 91°46'48"E; 15 August 2021, collected by Shibly Sadique Shashi.

Description of the male.

Carapace subhexagonal, convex, covered by short spongy fur, dorsal surface rough, region distinct; ca 1.19 × broader than long. H-shaped groove distinct. Epigastric cristae broad, blunt, well advance of postorbital cristae; post orbital cristae short, not confluent with first epibranchial tooth (Fig. 2a ); external orbital tooth blunt, broadly triangular; anterolateral margin convex, with 4 epibranchial teeth, first epibranchial tooth distinctly triangular, others sharp. Eyes moderate in size, outer margin of eye with U- to V-shaped incision (Fig. 2c ). Third maxilliped elongated, rectangular; with well-developed flagellum present distally on exopod; exopod not distally tapering and longer than merus width. Epistome lateral margins slightly sinuous, medial lobe triangular (Fig. 2c ).

Chelipeds unequal in size, right larger; carpus and merus of cheliped with distinct subdistal and subterminal spine, fingers longer than palm, distinct gap with dactyl and pollex closed, both movable and immovable fingers with 3 or 4 large, rounded teeth (Fig. 2d ); fingers of minor chela slightly gaping when closed (Fig. 2e ). Ambulatory legs bearing short setae; second pair of ambulatory legs longest, fourth pair shortest; dactylus slender, styliform, with spinules (Fig. 2a ).

Thoracic sternum smooth, pitted, suture between s1/s2 completely fused to form triangular structure; suture between s3/s4 indistinct, suture between s4/s5, s5/s6, s6/s7, s7/s8 distinct (Fig. 2b ).

Pleon broadly triangular; all segments rectangular. Telson tongue-shaped, length and width almost equal (Fig. 2b ).

G1 curved outwardly, gradually tapering towards tip; terminal segment subcylindrical, slender, covered by short setae; nearly 3 × shorter than subterminal segment (Fig. 4a, b ). G2 elongated, shorter than G1.

Remarks.

Acanthopotamon fungosum was originally described as Potamon (Paratelphusa) fungosum Alcock, 1909 from Cachar, India ( Bott 1970). Previously, A. fungosum was only known from the states of Arunachal Pradesh, Assam, Mizoram and Manipur, in India ( Pati et al. 2019; Mitra and Pati 2021; Rath et al. 2022). This species is recorded here for the first time from Bangladesh. Acanthopotamon martensi is also distributed in Bangladesh, i.e., in Manikganj district and estuaries of the Chakaria Sundarban area ( Shafi and Quddus 1982; Rahman et al. 2008).

The IUCN conservation status of A. fungosum was assessed as Data Deficient (DD) ( Cumberlidge 2008a). The species is distributed over a small geographical area, i.e., eastern Bangladesh and southern Assam, India. Due to restricted distributional range and increasing threats to freshwater habitats of this region from various human activities, A. fungosum is likely more threatened than M. edentula . Further field surveys are needed to determine population size and threats.

Until now, four species have been described for the genus Acanthopotamon ( Pati et al. 2019). Acanthopotamon fungosum can be easily differentiated by having four epibranchial teeth, compared to two epibranchial teeth in A. panningi ( Bott 1970: fig. 19; Pati et al. 2019), three in A. horai ( Pati et al. 2019), and three in A. martensi ( Bott 1970: fig. 20; Rahman et al. 2008; Pati et al. 2019).

Figures

Figure 2. Acanthopotamon fungosum a dorsal view b ventral view c frontal view d major chela e minor chela. Scale bars: 1 cm.

Figure 4. G 1 a, b Acanthopotamon fungosum c, d Maydelliathelphusa edentula. Scale bars: 2 mm.