Macrobrachium neglectum (De Man, 1905 )

Wowor, Daisy & Ng, Peter K. L., 2010, On the taxonomy of Palaemon javanicus Heller, 1862, and Palaemon sundaicus Heller, 1862, with description of a new species of Macrobrachium Bate, 1868 (Crustacea: Decapoda: Caridea: Palaemonidae) from Southeast Asia *, Zootaxa 2372 (1), pp. 278-297 : 283-287

Macrobrachium neglectum (De Man, 1905)

( Figs. 3–4 )

Palaemon acutirostris . — De Man 1888: 280, Pl. 18, Fig. 7 . — Ortmann 1891: 707 (nec Palaemon acutirostris Dana,

1852). Palaemon (Eupalaemon) equidens . — De Man 1892: 453, Pl. 26, Fig. 37 (nec Palaemon equidens Dana, 1852 ). Palaemon (Parapalaemon) javanicus . — Nobili 1900: 483. — Roux 1932: 571 (nec Palaemon javanicus Heller, 1862 ). Palaemon equidens . — Lanchester 1901: 565, Pl. 34, Fig. 4 (nec Palaemon equidens Dana, 1852 ). Palaemon (Eupalaemon) neglectus De Man, 1905: 201 , Pl. 15, Fig. 6 . — Chace & Bruce 1993: 14. Palaemon neglectus . — Kemp 1918: 265. Macrobrachium javanicum . — Holthuis 1950: 190, Fig. 38 (part). — Johnson 1963: 8 (part). — Chace & Bruce 1993: 29

(part) (nec Palaemon javanicus Heller, 1862 ). Macrobrachium javanicum neglectum . — Johnson 1960: 262, Figs 2 C-D, 3.

Macrobrachium neglectum . — Ng 1990: 196; 1997a: 268. — Ng & Choy 1990a: 304, 309; 1990b: 15. — Cai & Ng 2002: 62, Fig. 3 . — Cai et al. 2004: 590 . — Wowor et al. 2004: 353, Fig. 13W.

Macrobrachium neglectus . — Naiyanetr 1998: 32; 2007: 37.

Material examined. Type material. Palaemon (Eupalaemon) neglectus De Man, 1905 , male (tl 85.0, ZMA De 102.811a, lectotype designated herein), lower Batak landen, near Deli, North Sumatra; 2 paralectotypes ( ZMA De 102.811b), same data as lectotype; paralectotype male (tl 67.0, ZMA De 102.810, incorrectly identified as Palaemon acutirostris Dana, 1852 , by De Man, 1888), King Island, Mergui Archipelago.

Other Material examined: MYANMAR: see Cai & Ng (2002) for list; THAILAND: 25 specimens ( USNM 65508 ), Nam Chuet, Koh Chang, leg. H. M. Smith, 5.IV.1924 ; 4 males ( USNM 65574 ), Koh Chang, leg. H. M. Smith, 12.IV.1925 ; 1 male ( USNM 65507 ), Klong Raibon, Krat Province , leg. H. M. Smith, II.1927 ; 1 male ( USNM 65624 ), Tadi Stream, Ban Kiriwong; for more Thai records, see Cai et al. (2004); PENINSULAR MALAYSIA: 2 males ( RMNH D 16166), Sg. Sekolah, P. Langkawi, 7.XII.1960 ; 5 specimens ( NHM 1898.11.28), P. Pinang, leg. S. S. Flower, 8.III.1898 ; 6 males, 3 females, 5 ov. females ( ZRC), Kg. Tengah, P. Pinang, leg. H. H. Tan & S. H. Tan, 8.VI.1993 ; 1 male, 2 females, 2 ov. females ( ZRC), Chin Farm Waterfalls, Batu Ferringhi at Teluk Bahang, P. Pinang, leg. H. H. Tan, 9.VIII.2001 ; 1 male, 1 female ( ZRC), tributary of Sg. Korbu, Perak, leg. H. H. Tan, 17.XI.1995 ; 3 males ( ZRC), Sekayu Waterfall, Trengganu, leg. H. H. Tan, 16.V.1995 ; 2 males, 3 females ( ZRC), down river of Sekayu Waterfall, Trengganu, leg. H. H. Tan, 16.V.1995 ; 2 males, 2 females, 1 ov. female ( ZRC), Sg. Berang, tributary of Sg. Trengganu, Trengganu, leg. H. H. Tan, 21.X.1998 ; 1 male ( MZB Cru 2595), Sekayu Waterfall, Sekayu Recreation Forest , Trengganu, leg. O. Chia et al., 9.X.1997 ; 13 males, 8 ov. females ( ZRC), Sg. Berang, Kg. Sekayu, Hulu Trengganu, Trengganu, leg. P. K. L. Ng & D. Wowor, 8.X.1997 ; 2 males, 1 female ( ZRC), Sg. Mupor, Kota Tinggi, Johor, 21.VIII.1994 ; 3 males, 2 ov. females ( ZRC), foothill of Gn. Panti, Kota Tinggi, Johor, leg. P. K. L. Ng, 20.IX.1990 ; SUMATRA: 1 male, 3 ov. females ( MZB Cru 2596), Krueng Peuto, Cot Girek, Aceh Utara Regency, Aceh, leg. D. Wowor, 7.II.1984 ; 2 males, 1 female ( MZB Cru 2597), Sg. Lembang, Suag Balimbing Research Station , Gn. Leuser N.P., Aceh Selatan Regency, Aceh, leg. R. K. Hadiaty, 4.IX.1997 ; 1 female, 1 ov. female ( MZB Cru 2598), Sg. Lembang, Pasi Lembang, Aceh Selatan Regency, Aceh, leg. R. K. Hadiaty, 27.VIII.1997 ; 2 males ( MZB Cru 2599), Sikundur, Langkat Regency, N. Sumatra, leg. J. Sugardjito, 5.X.1978 ; 1 male ( MZB Cru 716), Sikundur, Langkat Regency, N. Sumatra, leg. J. Sugardjito, 5.X.1978 ; 1 male, 1 female ( MZB Cru 2600), Sg. Besitang, Sikundur, Langkat Regency, N. Sumatra, leg. S. Wirjoatmodjo & D. Hardjono, 9.II.1983 ; 1 male ( MZB Cru 2601), Sg. Besitang, Gn. Leuser N.P., Langkat Regency, N. Sumatra, leg. S. Wirjoatmodjo & D. Hardjono, 14.II.1983 ; 12 males, 5 ov. females ( MZB Cru 887), Sg. Besitang, Sikundur, Langkat Regency, N. Sumatra, leg. D. Wowor, 25.X.1981 ; 1 male, 1 ov. female ( MZB Cru 2602), Alur Di, a tributary of Sg. Besitang, Sikundur, Langkat Regency, N. Sumatra, leg. S. Wirjoatmodjo & D. Hardjono, 9.II.1983 ; BORNEO: 4 specimens ( NHM 1893.3.26.3-6), Sarawak River, leg. A. Everett ; 6 specimens ( NHM 1893.3.26.10-14), Sarawak River, leg. A. Everett ; 1 male ( ZRC), stream nearby Kubah N.P., Sarawak, leg. O. Chia, 26.VI.1998 ; 3 males ( ZRC), Sg. Sendok, Sg. Rayu basin, Matang Wildlife Centre, Kubah N.P., Sarawak, leg. T. Iwata, 1998 ; 1 male ( ZRC), Sg. Rayu, Matang Wildlife Centre, Kubah N.P., Sarawak, leg. T. Iwata, 20-21.XII.1997 ; 1 male ( ZRC), Sg. Rayu basin, Matang Wildlife Centre, Kubah N.P., Sarawak, leg. T. Iwata, 1998 ; 2 males ( SM), Sg. Joh, Sg. Katibas basin, Sarawak, leg. C. Leh, 10.X.1997 ; 1 male, 4 ov. females ( RMNH D 35315), Sg. Pelagus, Sarawak, leg. A. Lelek, 1-3.VIII.1981 ; 1 male ( ZRC), Kg. Matang, Sarawak, leg. H. H. Tan, 4.IX.1995 ; 3 males, 2 ov. females ( MZB Cru 2603), Matang, Sarawak, leg. L. W. Loh, VI.1998 ; 3 ov. females ( ZRC), Sg. Malinau Paku, at border of Gn. Mulu N.P., Sarawak, leg. D. Wowor, 19.IX.1998 ; 1 male, 1 ov. female ( ZRC), Sg. Adang, a tributary of Sg. Tutoh, outside of Gn. Mulu N.P., Sarawak, leg. D. Wowor, 19.IX.1998 ; 3 males, 3 females, 3 ov. females ( ZRC), Sg. Malinau at border of Gn. Mulu N.P., Sarawak, leg. D. Wowor, 18.IX.1998 ; 2 ov. females ( ZRC), Sg. Pala, confluent to Sg. Malinau, outside Gn. Mulu N.P., Sarawak, leg. D. Wowor, 17.IX.1998 .

Diagnosis. Rostrum short, 0.64–0.75 of cl, reaching or slightly behind distal end of scaphocerite; moderately slender, maximum depth about equal to maximum dorsoventral diameter of cornea; dorsal carina straight above orbit, bent downwards in front of orbit with tip directed anteriorly, teeth subequally distributed, armed with 9–12 teeth (mode 12), 2–4 teeth completely postorbital (mode 3 and 4), postorbital teeth on anterior 0.26–0.37 of carapace; ventral carina with 3 or 4 teeth (mode 4). Carapace with minute spinules ( Fig. 3A ). Epistome completely bilobed, lobes with blunt rounded margins ( Fig. 3C ).

Second pereiopods with distal quarter or half of minor cheliped carpus extending beyond end of scaphocerite. Major cheliped ( Fig. 4A ) with chela covered by spines and few scattered short stiff setae but not concealing cutting edges, 1.09–2.01 times CL, length 6.83–8.89 times width, outer and inner margins slightly convex and concave respectively; palm subcylindrical, greater than maximum merus width, slightly compressed, width 1.10–1.24 times depth; fingers 0.51–0.79 times palm length, gaping, distal half with a row of sharp spines on each side of cutting edge of each finger, tips uncinate; dactylus with 2 large teeth, first tooth at proximal 0.49, second tooth at proximal 0.21 and 2 smaller teeth towards articulation of fingers, pollex with 2 large teeth at proximal 0.44 and 0.16 respectively and 3 smaller teeth towards articulation of fingers, teeth unequally distributed along cutting edges; carpus 0.67–0.84 times palm length and 0.99–1.14 times merus length, conically long, length 3.11–4.31 times distal width; merus not inflated, 1.14–1.61 times ischium length. Minor cheliped ( Fig. 4B ) generally resembling major cheliped; chela covered with spines and few scattered short stiff setae; fingers 0.58–0.76 times palm length, gaping, distal 0.57 with a row of sharp spines on each side of cutting edge of each finger, each finger with 2 large teeth and 2–4 smaller teeth towards articulation, teeth distributed subequally along proximal 0.43.

Third pereiopods with tip of dactylus reaching distal end of scaphocerite; dactylus stout, curved, ventral carina poorly developed; propodus length 9.53–12.57 times longer than wide; pereiopods covered with spinules and few scattered medium-sized stiff setae ( Figs. 3J–K ).

T4 with small triangular median process and moderate posterior submedian plate ( Fig. 3D ); T8 with anterior lobes narrowly separated or contiguous posteriorly, without median process ( Fig. 3E ). First 2 male abdominal sternites with large triangular median process of similar size and form; third abdominal sternite with small median process ( Fig. 3F ). Inter-uropodal sclerite well developed, elevated as longitudinal preanal carina, carina medium-sized, slightly larger then posterolateral teeth of sixth abdominal somite. Telson moderate, stout, glabrous ( Fig. 3H ). Uropods with acute distolateral tooth, mobile mesial spine larger than distolateral tooth ( Fig. 3G ).

Remarks. De Man (1888) identified a specimen from the Mergui Archipelago as Palaemon acutirostris Dana. Ortmann (1891) later pointed out that this specimen is not P. acutirostris Dana , sensu stricto. De Man (1892) subsequently identified a series of prawns from Batak, near Deli from the east coast of Sumatra, as P. equidens Dana , evidently also incorrectly. In 1905, De Man corrected his 1888 and 1892 identifications and gave a new name to all these specimens, Palaemon (Eupalaemon) neglectus . As no holotype was designated, all the material examined by De Man (1888, 1892, 1905) are therefore syntypes of Palaemon neglectus . We hereby select the largest male specimen (tl 85 mm, ZMA De 102.811), collected from near Deli, North Sumatra, as the lectotype of Palaemon (Eupalaemon) neglectus De Man, 1905 . This is necessary to help stabilise the taxonomy of the species, especially in view of the past confusion between this species and what has long been called M. javanicum .

A male specimen of 91 mm long from Siboga [= Sibolga], north Sumatra, was identified by Nobili (1900) as P. (Parapalaemon) javanicus . Although the description is short, it is unlikely to be M. javanicum ( Heller, 1862) since the number of ventral rostral teeth is higher and the specimen is much larger than the maximum size of this species. Based on the combination of rostral length, rostral formula and body size as described, we believe Nobili’s specimen is actually M. neglectum as presently defined. The figure of the chela of the major second pereiopod of what was identified as P. equidens by Lanchester (1901) clearly shows that his specimen is also M. neglectum .

Palaemon neglectus was later synonymized under M. javanicum sensu De Man (1879) by Holthuis (1950). However, Johnson (1960) treated P. neglectus as a distinct subspecies, M. javanicum neglectum (see also Remarks for Macrobrachium duri spec. nov.). Ng & Choy (1990a, b) subsequently recognized M. neglectum as a valid species. Johnson (1960) mentioned populations exhibiting an intermediate morphology between M. neglectum and M. javanicum sensu De Man (1879) (presently M. duri spec. nov.) found in the region of Deli in northern Sumatra. A reasonable number of freshly collected specimens of this northern Sumatran population have been examined during the present study, and this “intermediate form” falls nicely within the morphological variation found in M. neglectum sensu stricto. The differences between these two species have been discussed at length by Wowor & Choy (2001) (see also Remarks under M. duri spec. nov.).

Ecology. The habitat of Macrobrachium neglectum is similar to that of M. duri spec. nov. It prefers large streams and small rivers with fast flowing waters, usually hiding in the dense vegetation along the banks or in sunken wood and logs. It has also been collected near waterfalls under rocks and debris and occasionally in swamp forest. The waters they occur in are not very acid, with a relatively moderate-oxygen content and cool temperature ( Johnson 1967; Ng & Lim 1992).

Distribution. Myanmar, Thailand, Mergui Archipelago, Peninsular Malaysia, Singapore, north and east coast of Sumatra, southern Sarawak on the west coast of Borneo.

Figures

FIGURE 2. Macrobrachium duri spec. nov., holotype male (cl 20.7, MZB Cru 1079): A, dorsal view of major second pereiopod; B, dorsal view of minor second pereiopod. Scale = 5.0 mm.

FIGURE 3. Macrobrachium neglectum (De Man, 1905), male (cl 21, MZB Cru 716): A, lateral view of carapace; B, postantennular carapace margin; C, epistome; D, T4; E, T8; F, first 3 abdominal sternites; G, mobile mesial spine of exopod of uropod; H, telson; I, first pereiopod; J, third pereiopod; K, dactylus of third pereiopod. Scales: A = 5.0 mm; B, E–F, H–J = 2.0 mm; C–D, G, K = 1.0 mm.

FIGURE 4. Macrobrachium neglectum (De Man, 1905), male (cl 21, MZB Cru 716): A, dorsal view of major second pereiopod; B, dorsal view of minor second pereiopod. Scale = 5.0 mm.

FIGURE 6. Macrobrachium sundaicum (Heller, 1862), lectotype male of Palaemon javanicus Heller, 1862 (cl 18.2, NHMW 7689a): A, dorsal view of major second pereiopod, setae on parts of fingers and distal palm omitted; B, dorsal view of minor second pereiopod. Scale = 5.0 mm.

FIGURE 7. Macrobrachium sundaicum (Heller, 1862), lectotype female of Palaemon sundaicus Heller, 1862 (cl 12.6, NHMW 1525a): A, lateral view of carapace; B, lateral view of second pereiopod; C, dorsal view of chela of second pereiopod. Scales: A = 5.0 mm; B–C = 2.0 mm.