Macrobrachium hendersoni (De Man, 1906) (figure 12) Palaemon hendersoni De Man, 1906: 405 [type locality: Darjeeling, northern India]; Kemp, 1913: 303, figures 19–23; 1918: 95; 1924: 41, pl. 3, figure 5; Tiwari, 1955a: 189; 1955b: 233. Palaemon yunnanensis Yu, 1936: 308, figure 3, 4 [type locality: Mann-Tchi-Pan, Yunnan, China]. Macrobrachium hendersoni: Holthuis, 1950: 209. Material examined North Thailand. Five WW, cl 15.2–19.5 mm, 1 ovigerous X, cl 7.0 mm, eggs 1.8× 1.3 mm (ZRC 2000.2729), Mae Sariang district, Mae Hong Son river, coll. Kitisan Suprepapon, 20 February 1994; 8 WW, cl 12.0–14.0 mm, 2 ovigerous XX, cl 13.7–15.0 mm (CU 1997.183), Mae Hong Son, 21 March 1978; 1 W, cl 8.5 mm, 2 ovigerous XX, cl 10.8–12.3 mm (CU 1997.187), Mae Hong Son, 21 March 1978; six specimens, Mae Hong Son, coll. P. Naiyanetr, 26 April 1986; 12 specimens (CU 1997.187), Mae Hong Son, 21 March 1978; 3 WW, cl 19.5–25.0 mm (CU 1997.109), no data; 1 W, 1 ovigerous X, Tha Song Yang, 17 May 1985. West Thailand. Three WW, cl 14.5–24.5 mm (CU 1997.109), near hot spring water, Hin Lad Amphoe, Thongphaphum, Kanchanaburi, 15 April 1985; 1 X, cl 9.2 mm (ZRC 2000.2709), Kanchanaburi: Mae Nam Khwae Noi basin: small forest tributary of Nam Khung, 14°36∞32◊N, 98°31∞52◊E, coll. M. Kottelat and K. Kubota, 3 April 1998; 1 ovigerous X, cl 14.5 mm, eggs 1.5×1.0 mm (ZRC 2000.2711), Tak Province: Mae Nam Moei at Ban Wale, coll. M. Kottelat and K. Kubota, 7 April 1998; 2 WW, cl 9.3–10.1 mm, 2 XX, cl 5.5–11.7 mm (ZRC 2000.2699), Kanchanaburi Province: Mae Nam Khwae Noi basin, Nam Khung, upstream of Ban Huai Pak Khung, riffles, between second ford and reservoir, coll. M. Kottelat and K. Kubota, 3 April 1998; 4 WW, cl 9.5–17.0 mm, 1 X, cl 8.0 mm, 1 ovigerous X, cl 13.0 mm, eggs 1.5× 1.1 mm (ZRC 2000.2657), road from Songkhla Buri to Kanchanaburi, km 12 on road going to small waterfall, coll. K. Kubota, April 1998; 6 WW, cl 6.4–9.6 mm, 8 XX, 1 ovigerous X, cl 11.1 mm, eggs 1.7× 1.3 mm (ZRC 2000.2735), Ratchaburi Province, Mae Nam Phachi basin, Nam Tok Suan Phung, coll. M. Kottelat and K. Kubota, 2 April 1998; 4 WW, cl 14.5–21.0 mm, 1 X, cl 12.0 mm (ZRC 2000.2659), Tak Province, Salwean basin, stream at km 57 on road Mae Sot-Wa Rai, 5 km before Wa Rai, 16°20∞8.2◊N, 98°41∞23.9◊E, coll. M. Kottelat, 8 November 1995; 2 WW, cl 13.5–18.2 mm, 1 X, cl 13.4 mm (ZRC 2000.2658), Tak Province, Salween basin, Mae Nam Moei at Ban Wa Rei, 16°17∞23.2◊N, 98°42∞19.66◊E, coll. M. Kottelat, 8 November 1995; 5 WW, cl 8.5–16.0 mm, 1 X, cl 8.5 mm (ZRC 2000.2662), Tak Province, Salween basin, Huey Moon Hing Leak Phai at Moon Hing Leak Phai, km 26, stone 22, on road Mae Sot-Umphang, 24 km before Phop Phra, coll. M. Kottelat, 8 November 1995; 6 WW, cl 8.4–13.5 mm (ZRC 2000.2663), Rachaburi Province, Suan Pheng District, Suan Pheng waterfall, 13°31∞12.6◊N, 99°14∞19.9◊E, coll. D. Yeo et al., 15 August 1997; 3 WW, cl 11.8–16.0 mm, 2 XX, cl 12.2– 11.6 mm (CU 1997.195), Sai Yok waterfall, Kanchanaburi; seven specimens, cl 10.5–12.0 mm, no data; three specimens, Sai Yok waterfall, Kanchanaburi, 18 August 1989; 1 W (CU 1997.178), Si Sawat, Kanchanaburi, 3 November 1979; two specimens (CU 1997.179), Phop Phra Tak, 7 January 1985; three specimens, Thong Pha Phum, Kanchanaburi, 21 July 1986; five specimens (CU), Phop Phra Tak, 13 August 1988; two specimens, Thong Pha Phum, Kanchanaburi, 5 May 1985; 2 WW (CU 1997.189), Sai Yok waterfall, Kangchanaburi; 20 specimens (CU 1997.185), Thap Sakae, Prachuap Khiri Khan, 22 June 1977; three specimens, Suan Pheng Raichabai, no data; 1 W, cl 15.5 mm, 1 X, cl 11.0 mm, 1 ovigerous X, cl 11.0 mm, eggs 2.2× 1.8 mm (ZRC 2000.2710), Kanchanaburi Province: Mae Nam Khwae Noi basin: Huai Kroeng Kawia, on road from Thong Pha Phum to Thung Yai National Park, coll. M. Kottelat and K. Kubota, 4 April 1998; 1 W, cl 23.3 mm, 2 XX, cl 10.0– 10.5 mm (ZRC 2000.2661), Tak Province: Mae Nam Moei basin, Huai Mae Lamno, about 2 km north of road 105, on road going to Ban Mae Lamao and Ban Mae Ramat, coll. M. Kottelat and K. Kubota, 6 April 1998; 1 W, 17.5 mm (CU 1997.116), Sai Yok waterfall, Kanchanaburi, coll. P. Naiyanetr, 18 August 1989. Diagnosis Rostrum short, or slightly convex at dorsal margin, reaching to end of second segment of antennular peduncle, or to end of antennular peduncle, mostly reaching distal half of third segment of antennular peduncle. Antennal and hepatic spines present. Antennular peduncle 0.6 times as long as carapace. Scaphocerite 2.8 times as long as wide. First pereiopod reaching with entire chela beyond distal end of scaphocerite, fingers slightly shorter than palm; chela 0.65 times as long as carpus. Second pereiopods unequal in length, similar in form. Major second pereiopod slightly shorter than body, with one-third of carpus reaching beyond distal end of scaphocerite; carpus cylindrical, shorter than merus, half length of palm; palm slightly broader than carpus, fingers subequal to palm in length, with distinctive longitudinal grooves, densely covered by velvety setae, fingers not gaping even when closed, with two pairs of strong teeth at proximal half of cutting edge, proximal tooth of fixed finger blunt, with two or more tubercles distally. Third pereiopod reaching with entire dactylus beyond distal end of scaphocerite; propodus seven times as long as wide, 2.1 times as long as dactylus. Uropodal diaeresis with a spine much smaller than outer angle. Ovigerous female with egg size 1.7–2.2× 1.4–1.8 mm in diameter. Remarks Compared to the types (see De Man, 1906), the rostrum of the Thai specimens are slightly longer, but still fall within the concept of M. hendersoni hendersoni as defined by Tiwari (1952). The form of the setae-clothed fingers and the distinctive shape of the proximal tooth at the fixed finger, described in detail by Kemp (1913), are very characteristic for the species. Tiwari (1952) had described two subspecies, Palaemon hendersoni platyrostris and P. h. cacharensis, both from Assam, northern India. According to the original description, P. h. platyrostris has a rostrum that is longer than P. h. hendersoni, reaching to the end of the antennular peduncle, and deeper than the latter. Palaemon h. cacharensis resembles P. h. platyrostris in the character of the rostrum and the shape of second pereiopod, but its main distinguishing feature is the absence of the longitudinal grooves and pubescence on the distal part of the fingers of the male second pereiopod. The form of the carpus is quite different between M. hendersoni hendersoni and Tiwari’s two subspecies, i.e. it is short, and cup-shaped in the nominal subspecies but elongate in the other two. Since the differences are so obvious and consistent, Cai and Ng (in press) recently treated these taxa as three separate species. Six more species in this group were recognized by Tiwari (1955a; 1968), mamely M. cavernicola (Kemp, 1918), M. assamense (Tiwari, 1968), M. peninsularis (Tiwari, 1968), M. siwalikensis (Tiwari, 1952), M. dayanum (Henderson, 1893) and M. hendersodayanum (Tiwari, 1952).

Published as part of Cai, Y., Naiyanetr, P. & Ng, P. K. L., 2004, The freshwater prawns of the genus Macrobrachium Bate, 1868, of Thailand (Crustacea: Decapoda: Palaemonidae), pp. 581-649 in Journal of Natural History 38 (5) on pages 615-617, DOI: 10.1080/0022293021000033238, http://zenodo.org/record/5258702