Eurycarcinus bengalensis Deb, 1999

Trivedi, Jigneshkumar, Mitra, Santanu, Patel, Pooja, Maheta, Niketa, Patel, Krupal & Ng, Peter K. L., 2021, On the Indian species of Eurycarcinus A. Milne-Edwards, 1867, Heteropanope Stimpson, 1858, and Pilumnopeus A. Milne-Edwards, 1867 (Decapoda: Brachyura: Pilumnidae), Nauplius (e 2021004) 29, pp. 1-18 : 5-9

Eurycarcinus bengalensis Deb, 1999

( Figs. 3, 4, 9G–I)

Eurycarcinus bengalensis Deb, 1999: 376 (part), fig. 2.

Heteropanope bengalensis — Ng et al., 2018: 474; Trivedi et al., 2018: 59.

Material examined. Holotype, male (CW 25.1 mm; CL 16.9 mm), ZSI-C3349/2, Chamta Block, Sunderbans Tiger Reserve , West Bengal State, India, coll. S. Bhuinya. Paratypes, 2 males (CW 11.5 mm; CL 7.8 mm, CW 11.7 mm; CL 8.6 mm), data as per holotype.

Remarks. Deb (1999) described E. bengalensis on the basis of a holotype and an unspecified number of specimens collected from Sundarbans Tiger Reserve, West Bengal state, India. Ng et al. (2018) provisionally transferred this species to Heteropanope on the basis of the figure and description of the type specimen given in Deb (1999). In the present study, the type specimens of the species were examined and identified as Eurycarcinus because the thoracic sternite 8 of the specimen remains exposed when the male pleon is closed ( Fig. 3E) and pleonal somite 3 is relatively wider, with the lateral margin projecting ( Fig. 3C), which are characteristics of Eurycarcinu s.

The type series of E. bengalensis is mixed. Of the five specimens, the two paratype males agree well with the holotype male in most aspects and are clearly conspecific.The two ovigerous females (CW 13.9 mm, CL 10.4 mm; CW 21.3 mm, CL 15.3 mm), however, belong to E. integrifrons instead. The carapace shape and features ( Fig. 4) are clearly of this species.

Eurycarcinus bengalensis s. str. is similar to E. integrifrons in the following characters: the carapace is not prominently swollen and high in frontal view ( Figs.2A, 3A, 4A), the frontal margin is weakly bilobed ( Figs. 2B, 3B, 4B), there are distinct clumps of short setae between the first to third anterolateral teeth ( Figs. 2A, 3A, 4A), the supraorbital margin is smooth without granules, the sub-orbital and pterygostomial regions are smooth and glabrous with dense setae only along the sutures ( Figs. 2B, 3B, 4B), and the posterior margin of the epistome has the median lobe truncate, protruding anteriorly and separated from lateral margin by distinct rounded angle ( Figs. 2B, 3B, 4B). Eurycarcinus bengalensis , however, differs from E. integrifrons in several characters that cannot be explained by variation: the carapace of E. bengalensis is proportionately wider ( Figs. 3A, 4A) (more quadrate in E. integrifrons ; Fig. 2A); the anterolateral teeth are lobiform and wide, separated from each other by a fissure ( Figs. 3A, 4A) (more narrow dentiform anterolateral margin with the teeth separated by a U-shaped hiatus in E. integrifrons ; Fig 2A); the male chela is proportionately shorter ( Fig. 3D) (more elongate in E. integrifrons ; Fig 2D); male pleonal somite 6 is distinctly trapezoidal in shape ( Fig. 3C) (less so in E. integrifrons ; Fig. 2C); male pleonal somites 1–3 are proportionately less broad ( Fig. 3E) (proportionately wider in E. integrifrons ; Fig. 2E); and the distal part of the G1 is relatively shorter with the tip gently upcurved ( Fig. 9G, H) (G1 distal part relatively longer with the tip almost straight or gently curved downwards in E. integrifrons ; Fig. 9D, E).

The relative width of the carapace and proportions of male pleonal somites 1–3 of E. bengalensis ( Figs. 3A, 4A, 3E) are actually closer to the condition in E. orientalis ( Figs. 1A, E) but the other characters (notably carapace shape, anterolateral armature, posterior margin of the epistome, male pleon shape and G1) do not match.

The characters possessed by E. bengalensis are interesting. While its carapace closely resembles species of Heteropanope as indicated by Ng et al. (2018), the male sternal and pleonal characters are those of Eurycarcinus . It is possible that some, if not all the records of “ Eurycarcinus natalensis ” and “ Eurycarcinus orientalis ” from the eastern Indian Ocean ( e.g., Dev Roy, 2008; Rath and Dev Roy, 2009; see under E. orientalis ) actually belong to E. bengalensis instead. The material will need to be examined.