On the two ‘ forms’ of Dotilla intermedia De Man, 1888 (Crustacea: Brachyura Dotillidae) from the Bay of Bengal, India, with description of a new species Author Mitra, Santanu Zoological Survey of India, F. P. S. Building, 27 J. L. Nehru Road, Kolkata- 700016, West Bengal, India. Author Trivedi, Jigneshkumar N. Department of Life Sciences, Hemchandracharya North Gujarat University, Patan, Gujarat, India. Author Mendoza, Jose Christopher E. Lee Kong Chian Natural History Museum, Faculty of Science, National University of Singapore, 2 Conservatory Drive, 117377 Singapore. jcmendoza @ nus. edu. sg; https: // orcid. org / 0000 - 0001 - 9729 - 5703 text Zootaxa 2020 2020-07-08 4809 3 521 534 journal article 21532 10.11646/zootaxa.4809.3.6 4bd957a1-4346-4339-bb01-293e2f3c31f1 1175-5326 3936887 46DA13F2-1B01-4E07-B134-BCBEFAB44A73 Dotilla intermedia De Man, 1888 ( Figs. 1 , 2 , 3 , 4 , 5 , 7B, 7C, 7E , 8B, 8C, 8D, 8F, 8G ) Dotilla intermedia De Man 1888: 135 , pl. 9 figs. 4–6; Tesch 1918: 45 (key); Gordon 1941: 137 , fig. 11c; Vogel 1984: 225 , figs. 2a, 4; Bairagi 1995: 274 ; Radhakrishnan et al . 2006: 48 (list); Ng et al . 2008: 235 (list); Sahoo et al . 2008: 178 (list); Rath & Dev Roy 2010: 40 ; Dev Roy & Bhadra 2011: 208 ; Allen et al. 2011: 2 , figs. 1–5; Trivedi et al . 2018: 34 (list). Dotilla clepsydrodactylus Alcock 1900: 367 ; Alcock & McArdle 1902: pl. 63 figs. 2, 2a; Kemp 1915: 226 ; Ng et al . 2008: 235 (list). Dotilla intermedia (“high form”), Kemp 1919: 326 (key), 331, figs. 9f, 10a, d, e; Dev Roy & Bhadra 2005: 512 . Material examined. Types: Paralectotypes , 8 males , CW 3.7–4.2 mm , CL 3.1–3.5 mm , 6 females CW 3.2–4.3 mm , CL 2.8–3.6 mm ( ZSI-C8236 /6), Sullivan Island (= Lambi Island ), Mergui Archipelago, Myanmar , coll. J. Anderson , 1881–1882 . Lectotype (here designated) of D. clepsydrodactylus Alcock, 1900 , male, CW 6.5 mm , CL 5.0 mm ( ZSI 438– 45/7), intertidal, sandy beach, False Point, Odisha , India , coll. RIMS Investigator , 1893 –1894. Paralectotypes (here designated) of D. clepsydrodactylus Alcock, 1900 , 4 males , CW 5.8–7.2 mm , CL 4.7– 3.6 mm , 3 females , CW 6.8–7.9 mm , CL 4.5–5.3 mm ( ZSI 438–45 /7), same data as lectotype . Others: 104 males , CW 2.3–5.5 mm , CL 1.8 – 4.9 mm , 44 females (12 ovigerous), CW 3.1–7.5 mm , CL 2.6– 6.7 mm ( ZSI-C9192-3 /10) Chandipur , Balasore , Odisha , India , coll. F.H. Gravely , between June 1915 – May 1917 ; 25 males , CW 9.6– 8.5 mm , CL 7.9– 6.7 mm , 14 females CW 7.6–8.4 mm , CL 5.9–6.8 mm ( ZSI-C7963 /2), Digha coast, West Bengal , India , coll. S. Mitra , July 2017 . Description. See Allen et al. (2011) for a detailed description. Remarks. De Man (1888: 135 , 136) described Dotilla intermedia from “ 32 specimens , all males” collected from the Mergui Archipelago, in the eastern extent of the Bay of Bengal. It is important to note that he described the chelae as long, very slender, and denticulate, and the specimen illustrated ( De Man, 1888: 136 , pl. 9 figs. 4–6) does not show the characteristic chelar morphology, particularly the lobiform teeth, of the adult male as described by Kemp (1919) for his “high form”. It is likely that De Man may have confused some female specimens as males. The female Dotilla intermedia tend to have more slender chelae, without the pronounced teeth at the cutting edges, and their pleons are only slightly broader than those of the males, making them difficult to distinguish from the latter without close examination (see Fig. 3 ). This was confirmed by our examination of the syntype material (deposited in ZSI), where the diagnostic chelar morphology was observed in the males (see Fig. 2C ). FIGURE 1. Dotilla intermedia De Man, 1888 male (CW 9.6 mm, CL 7.9 mm) (ZSI-C7963/2), Digha, West Bengal. A, habitus, dorsal view; B, frontal view; C, right chela, outer view; D, thoracic sternum and pleon, ventral view. On the Indian Dotilla intermedia , Kemp (1919) stated that: “In the ‘high’ male, the first abdominal sternum [= 4 th thoracic sternite] bears a sharp transverse ridge on either side of the trough formed to receive the terminal segment of the abdomen [= telson] and well behind its anterior limit. The fingers of the chela bear a large lobe or tooth near the middle of their prehensile edge. The copulatory appendage [= G1] is blunt at the tip and furnished with numerous setae.” ( Kemp 1919: 331 , figs. 9f, 10a, d, e; see also Figs. 1C, 1D , 2C, 2D , 8B, 8C ). Since De Man (1888) did not indicate a holotype for D. intermedia from among the material he examined, in accordance with Article 73.2 of the International Code of Zoological Nomenclature (ICZN 1999), all such material effectively were syntypes . Allen et al. (2011) formally selected a lectotype (male, CW 3.9 mm ; ZMA 102540 ) from among the syntypes of D. intermedia deposited in the Zoological Museum, Amsterdam, the Netherlands , and provided a modern description for this species, with all other syntypes becoming paralectotypes (viz., Article 74; ICZN 1999). They, however, did not provide illustrations of the lectotype or paralectotypes , opting instead to illustrate a male specimen from Laem Son National Park ( Thailand ) further south. Nevertheless, with this action, D. intermedia s. str. conforms most closely with Kemp’s “high form” (as well as morphologies reported by Gordon 1941 ; Vogel 1984 ), characterized by the presence of four lobules on the carapace gastric region, a pronounced lobiform tooth on the cutting edge of both fingers of the chela, a tympanum on each of the ambulatory meri, two transverse cristate ridges on either side of thoracic sternite 4 posterior to the tip of the sternopleonal cavity, and a stout G1 with a blunt distal tip that is provided with several stiff setae ( Figs. 1A, 1C, 1D , 2A, 2C, 2D , 3A , 5B , 8B, 8C ; also Kemp 1919 : fig. 10a, d, e; Allen et al. 2011 : figs. 1a, 3a, b, 4a, b, 5a–d). The lectotype of D. intermedia is presently deposited in the Naturalis Biodiversity Center, Leiden, the Netherlands , along with an unspecified number of paralectotypes (C. Fransen, pers. comm.). This material could not be accessed by the authors, however, due to quarantine restrictions caused by the ongoing COVID- 19 pandemic. Nonetheless, more paralectotypes ( 8 males , 6 females ) were also found in the collection of the Zoological Survey of India in Kolkata, and a representative male ( Figs. 2 , 5A , 8C ) and female ( Fig. 3 ) are figured here. FIGURE 2. Dotilla intermedia De Man, 1888 paralectotype, male (CW 4.2 mm, CL 3.5 mm) (ZSI-C8236/6), Sullivan I., Mergui Archipelago. A, habitus, dorsal view; B, frontal view; C, right chela, outer view; D, thoracic sternum and pleon, ventral view. FIGURE 3. Dotilla intermedia De Man, 1888 paralectotype, female (CW 4.3 mm, CL 3.6 mm) (ZSI-C8236/6), Sullivan I., Mergui Archipelago. A, habitus, dorsal view; B, frontal view; C, right chela, outer view; D, thoracic sternum and telson, ventral view. Dotilla clepsydrodactylus Alcock, 1900 ( Figs. 4 , 7C , 8D, G ) was described from 8 specimens ( syntypes viz. Article 73.2 of the Code; ICZN 1999) collected from the intertidal zone of False Point, Mahanadi Delta, Odisha , India , on the western edge of the Bay of Bengal. It was subsequently considered a junior synonym of D. intermedia by Kemp (1919) , particularly to his “high form” due to similarities in the carapace morphology. The present examination of the 5 surviving syntypes of D. clepsydrodactylus in the collection of the Zoological Survey of India , Kolkata, affirms the synonymization by Kemp. The morphology of the carapace, chelipeds and ambulatory legs closely matches that of D. intermedia , although there are slight variations in the morphology of the male pleon, G1, and G2 (see Figs. 4D , 7C , 8D, G ), but these are not consistent among all the syntypes . Due to the condition of the syntypes , it is possible that these differences are artefacts and not real. Nevertheless, in accordance with Article 74 of the Code (ICZN 1999) a lectotype (male, CW 6.5 mm , CL 5.0 mm, ZSI 438–45/7) ( Figs. 4 , 7C , 8D, G ) is designated here to stabilize the taxonomy of this species, with the remaining syntypes becoming paralectotypes . Dotilla intermedia s. str. is currently known from both sides of the Bay of Bengal: i.e. , Sullivan Island, Myanmar ( type locality), Laem Son National Park, Thailand , and along the coasts of Kerala ( Radhakrishnan et al. 2006 ; Dev Roy et al. 2009 ); Tamil Nadu ( Kemp 1919 ; Sethuramalingam & Khan 1991 ; Dev Roy & Bhadra 2011 ; Dev Roy & Nandi 2007a ); Andhra Pradesh ( Dev Roy & Nandi 2007b ; Dev Roy 2008 ; Rath & Dev Roy 2009 , 2010 ); Orissa ( Alcock 1900 ; Deb 1995 ; Sahoo et al. 2008 ); West Bengal ( Dev Roy & Nandi 2001 ) in India ( Trivedi et al. 2018 ).