Macrobrachium hirsutimanus (Tiwari, 1952)

Cai, Y., Naiyanetr, P. & Ng, P. K. L., 2004, The freshwater prawns of the genus Macrobrachium Bate, 1868, of Thailand (Crustacea: Decapoda: Palaemonidae), Journal of Natural History 38 (5), pp. 581-649 : 621-628

Macrobrachium hirsutimanus (Tiwari, 1952)

(figure 15)

Palaemon hirsutimanus Tiwari, 1952: 31 [type: Doi Chuang , North Thailand].

Material examined

N: W, cl 15 mm ( ZRC 2000.2668 ), forest stream 95 km north from Nan Town , Nan Province, about 15–20 km north from Ban Pon, Nam Gae, north of Ban Sala, near Laos, North Thailand, coll. Y. Cai, 11 June 1998 .

North Thailand. Four WW, cl 13.3–16.0 mm, 1 X, cl 11.0 mm, 7 ovigerous XX, cl 9.6–10.5 mm ( ZRC 2000.2664 ), forest stream 95 km north from Nan town, Nan Province, about 15–20 km north from Ban Pon, Nam Gae, north of Ban Sala , near Laos, coll. Y. Cai, 11 June 1998 ; 3 XX, cl 10.2–12.9 mm ( ZRC), Nam Wa river at Ban Nam Wa, Nan, coll. A. Dot, 31 Jane 1992; 2 XX, cl 9.7–12.5 mm ( ZRC 2000.2665 ), Mae Nam Lin, stream, 14 km to Mae Khachan , 33 km to Wiang Pa Pao , 55 km to Chiang Mai , 19°6∞46.7◊N, 99°28∞35.8◊E, pH 8.2, coll. Y. Cai et al., 13 June 1998 ; 1 X, cl 11.3 mm (CU), Chiang Mai , 4 November 1977 ; 2 WW, cl 16.3–17.0 mm (CU 1997.153), Uttaradit, no date; 4 WW, cl 10.0–11.0 mm, 1 ovigerous X, cl 11.6 mm, eggs 1.5× 1.2 mm, CU1997.122, Phrae , 28 December 1988 ; 1 W (CU1997.139), Fang, Chiang Mai, coll. Bwn Ket, 17 May 1976; 5 WW cl 14.5–15.5 mm, 1 X, cl 14.0 mm, 2 ovigerous XX, (CU 1997.140), Lampang , 12 February 1977; 1 specimen (CU 1997.142) , Chiang Mai, 4 November 1977; four specimens (CU 1997.193), Lampang, 19 May 1996; one specimen (CU), Chiang Mai, coll. P. Naiyanetr, 20 April 1976.

North-east Thailand. Ten WW, cl 8.2–13.0 mm, 3 XX, cl 6.0– 11.4 mm ( ZRC 1997.119 ), Nakhon Rachasima (Korat) Province, outlet of Lam Takong reservoir, 14°15∞53.3◊N, 101°33∞53.4◊E, coll. H. H. Tan et al., 16 January 1997 ; 8 WW, cl 8.0–12.0 mm ( ZRC 2000.2666 ), Lam Thakong, outlet of dam at upper Mae Nam Mun, way from Sara Buri to Ratchasima , 14°52∞3.1◊N, 101°33∞35.3◊E, pH 8.9, coll. Y. Cai et al., 16 June 1998 ; 11 WW, cl 8.3–15.2 mm (CU 1997.137), Ubon Ratchathani, coll. P. Naiyanetr, no date; 1 W, cl 16.8 mm (CU 1997.141), Nakhon Ratchathani, 6 June 1980; four specimens (CU 1997.160) , Maha Sarakham, no date.

West Thailand. Six WW, cl 10.3–14.3 mm (CU), Tak, 16 December 1984 .

Central Thailand. Seven WW, cl 12.3–15.0 mm, 1 ovigerous X, cl 9.6 mm, eggs 1.4× 1.05 mm (CU), Uthathani , February 1986; 17 specimens (CU) , Uthathani , 6 February 1986; 31 specimens (CU) , Lan Sak Uthathani, coll. P. Naiyanetr, 30 January 1982.

East Thailand. 15 WW, cl 9.0–12.0 mm, 5 XX, cl 9.0–10.0 mm ( ZRC 1997.124 ), Chantaburi Province, Klong Pheet (stream) ca 35 km from Trat, 12°28∞4.5◊N, 102°37∞7.1◊E, coll. H. H. Tan, 14 January 1997; five specimens ( ZRC 2000.2667 ) , waterfall, 22 km turn off from main road, 15°38∞59.0◊N, 101°25∞9.0◊E, coll. Y. Cai, 20 June 1998; 6 WW, cl 8.0–11.0 mm, 5 XX, cl 8–14 mm ( ZRC 2000.2689 ), Trat Province, Nam Tok Salas Phai, about 5–10 km north-west of road 3157, coll. M. Kottelat et al., 3 December 1993 .

Diagnosis

Rostrum reaching to third segment of antennular peduncle or slightly beyond tip; dorsal margin slightly convex, rostral formula: 3–5+6–7/1–4 (mode 2), carapace slightly inflated laterally, surface smooth. Eyes about 0.15–0.20 times of carapace length. Second pereiopods as long as, or slightly longer than body length, distinctly unequal in adult males; merus cylindrical, distal half more inflated than proximal half, outer surface with numerous spinules; chela covered with dense, long pubescence; fingers elongate, slender, subequal to palm; cutting edge with 12–20 closely spaced teeth and denticles; third pereiopod with propodus stout, 2.0–2.5 times as long as dactylus; eggs 1.4–1.7×1.0– 1.25 mm in diameter.

Description of neotype

Rostrum (figure 15A) short, slightly convex, reaching beyond end of second segment, but not end of antennular peduncle, dorsal margin of rostrum with 10 teeth, ventral with two to four dorsal teeth situated behind postorbital margin, occupying about one-third length of carapace, teeth above eye more closely spaced than rest. Antennal spine sharp but short, situated below lower orbital angle. Hepatic spine smaller than antennal spine, lying behind and distinctly below latter. Carapace smooth.

Third thoracic sternite with indistinct transverse ridge, fourth thoracic sternite without projection. Abdomen smooth, glabrous, first to third pleurites broadly rounded, fourth and fifth feebly produced posteriorly, fourth subtriangular, fifth subrectangular, sixth abdominal somite 1.6 times as long as fifth one, with posterolateral angle strongly produced, acute, posteroventral angle produced feebly, subacute. Telson (figure 15D) 1.4 times length of sixth abdominal segment, with two pairs of small dorsal spines, ending in a median point, lateral spines small, smaller than dorsal spines, intermediate spines well developed, with about six pairs of long plumose setae. First to third abdominal sternites (figure 15C) with transverse ridge, with median tooth, that of second abdominal sternite largest, that of third less prominent. Preanal region with rounded ridge.

Eyes well developed, cornea longer, broader than stalk, 0.15 times as long as carapace. Basal segment of antennular peduncle broad. Stylocerite distinctly pointed, reaching middle of basal segment. Anterolateral tooth reaching about middle of second segment. Second segment longer than third segment. Antenna with stout basicerite, with strong distoventral tooth, carpocerite reaching to about 0.4 times of scaphocerite length. Scaphocerite (figure 15E) 3.1 times as long as broad, with straight outer margin.

Epistome as in figure 15B, bilobed by depression. Mouth parts typical of genus.

First pereiopods (figure 15F) very slender, reaching beyond scaphocerite by half of carpus, equal in length, similar in form. Palm 1.3 times as long as fingers, carpus 1.7 times as long as chela, merus shorter than carpus, twice as long as ischium. Second pereiopods unequal. Major second pereiopod (figure 15G, H) as long as body length (rostrum excluded), reaching beyond scaphocerite by carpus. Fingers (figure 15I) of chela straight, with curved pointed tips, slightly gaping when closed, shorter than palm, with about 15 blunt teeth along both cutting edges. Palm slightly inflated, 2.6 times as long as broad, with densely packed long velvety setae on whole surface, setae more densely packed dorsally than ventrally. Carpus short, conical, about 0.3 times as long as chela. Merus 2.0 times as long as carpus. Minor second pereiopod short, about 0.8 times of body length, fingers longer than palm, with numerous blunt teeth on both cutting edges. Chela 1.8 times as long as carpus. Merus 1.5 times as long as carpus, with setae as on major second pereiopod. Third pereiopod (figure 15J, K) reaching end of scaphocerite. Dactylus slender, pointed, 2.8 times as long as broad. Propodus 2.5 times as long as dactylus, with about six spinules on posterior margin.

Endopod of male first pleopod with concave inner margin, outer margin convex. Appendix masculina of male second pleopod longer, stouter than appendix interna, with numerous stiff spines.

Uropodal diaeresis (figure 15L) with movable spine, weaker, shorter than outer angle.

Remarks

Tiwari (1952) established M. hirsutimanus from northern Thailand with a very short diagnosis. This species has never been reported and has been totally ignored since. It has also been ignored by all workers on the Macrobrachium pilimanus species group although the original diagnosis clearly indicates that it is a member of this group (see Johnson, 1960; Holthuis, 1979; Dai, 1984; Chong, 1989; Chong and Khoo, 1987a, 1987c; Ng, 1995). According to the original diagnosis, the rostral formula of M. hirsutimanus is unclear. In the text, Tiwari (1952) stated that the rostral formula is 1–3+7–8/1. However, he also mentioned that the rostral form and the formula were the same as M. latimanus, which has a formula ‘2–3+7–8/2–4’. The rostral formula of M. hirsutimanus , as stated by Tiwari (1952), in fact, is an extremity of specimens from northern Thailand, and most probably, is a typographical mistake. The type material is supposedly deposited in the Zoological Survey of India but could not be located and is probably lost (H. H. Ng and D. Yeo, personal communication). To stabilize the taxonomic status of M. hirsutimanus , as well as the M. pilimanus species group, we hereby designate a neotype (a W, cl 15 mm, ZRC 2000.2668, northern Thailand) for M. hirsutimanus and redescribe it in detail.

To date, there are 12 recognized species in the Macrobrachium pilimanus group, namely M. pilimanus (De Man, 1879) , M. leptodactylus (De Man, 1892) , M. hirsutimanus (Tiwari, 1952) , M. dienbienphuense Dang and Nguyen, 1972 , M. eriocheirum Dai, 1984 , M. ahkowi Chong and Khoo, 1987, [= M. johnsoni Chang and Khoo, 1987c.] M. gua Chong, 1989, M. forcipatum Ng, 1995 , M. platycheles Ou and Yeo, 1995, M. pilosum Cai and Dai, 1999, M. amplimanus Cai and Dai, 1999 , and M. sirindhorn Naiyanetr, 2001 (see also Cai and Dai, 1999; Naiyanetr, 2001). With regards to the presence of pubescence on the merus, this can be used to easily distinguish M. sirindhorn and M. pilosum from other members of the M. pilimanus species group. As such, M. pilosum and M. sirindhorn are here not regarded as members of the M. pilimanus species group. Among members of the M. pilimanus species group, M. hirsutimanus most closely resembles M. pilimanus , M. eriocheirum and M. forcipatum , in the form of rostrum and the pereiopods. Macrobrachium hirsutimanus can be distinguished from M. pilimanus (cf. lectotype, here designated: W, cl 14.5 mm, RMNH D 1477, Moearalaboeh, West Sumatra, Indonesia, Midden Sumatra Expedition, 1877; paralectotypes: 3 WW, cl 8.0– 12.6 mm, 1 X, cl 13.4 mm, data same as lectotype; 3 WW, cl 10.6–13.5 mm, 2 XX, cl 9.5–12.5 mm, 2 ovigerous XX, cl 12.0– 12.5 mm, with eggs 1.5–1.75×2.0 mm (ZMA-De 240494), Kotaboro in swamp, Padang Pandjang, Sumatra, Indonesia, leg. E. Jacobson, February 1925; 3 WW, cl 9.8–13.5 mm, 1 X, cl 13 mm, Lake Danau di Bawah, Sumatra, Indonesia, leg. Weber, 1949) by the more prominent processes on the abdominal sternites (figure 15C versus figure 16D); the form of the epistome (figure 15B versus figure 16C); the propodus of the third pereiopod 2.0–2.5 times being as long as the dactylus (versus 3.2 times); the postorbital teeth being more widely spaced than the anterior (versus closer spaced); the postorbital teeth occupying 0.33 times the length of the carapace (versus 0.15–0.20 times) and the smaller egg size (1.0–1.2× 1.4–1.6 mm versus 1.5–1.75×2.0 mm). It can be separated from M. eriocheirum by its bilobed epistome (versus trilobed; see figure 15B versus 18B); the less prominent process on the third abdominal sternite (figure 15C versus figure 18C) and the propodus of the third pereiopod being 2.0–2.5 times as long as the dactylus (versus 3.3 times). Macrobrachium hirsutimanus differs from M. forcipatum by the more prominent process on the third abdominal sternite (figure 15C versus figure 19C); the propodus being 2.0–2.5 times as long as the dactylus (versus 2.6–3.0 times), and the more numerous but smaller teeth on the cutting edges of male second pereiopods (12–20 versus less than 10).

As far as is known, M. hirsutimanus is distributed in north Thailand, north-east Thailand and central Thailand. It is commonly sold in local markets in these areas.

Lumubol (1980: 503) reported M. esculentum from Lam Nam Phong, Khon Kaen, north-east Thailand. This record was followed by Naiyanetr (1998: 32). It is, however, very doubtful as indicated by the attached figure, which clearly shows the characteristic pubescence covering the whole surface of chela, carpus and merus of the second pereiopod, a character which does not occur on any known Thai species of Macrobrachium. It is most probably a member of the Thai Macrobrachium pilimanus group.