Macrobrachium duri, Wowor & Ng, 2010

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 : 279-283

Macrobrachium duri spec. nov.

( Figs. 1 , 2 )

Palaemon Javanicus. — De Man, 1879: 180 (nec Palaemon javanicus Heller, 1862 ).

Palaemon (Parapalaemon) javanicus . — De Man 1892: 457, Pl. 26, Fig. 38 (nec Palaemon javanicus Heller, 1862 ).

Macrobrachium javanicum . — Holthuis 1950: 190, Fig. 38 (part). — Chace & Bruce 1993: 29 (part). — Wowor & Choy 2001: 284. — Wowor et al. 2004: 353, Fig. 13U.

Macrobrachium javanicum javanicum . — Johnson 1960: 262, Figs. 2–B , 3 .

Material examined. Male holotype (cl 20.7) ( MZB Cru 1079), Banten, Banten Province, Java, leg. D. I. Hartoto, VIII.1983 ; 1 male, paratype (cl 19.4) ( MZB Cru 2594), same data as holotype; 1 male, paratype (cl 27.6) ( ZRC 2009.0764 ), Sg. Banjaran, Desa Kedung Wuluh , Banyumas Regency, C. Java, leg. Setijanto, X.1984 .

Other Material examined: JAVA: 1 male ( RMNH D 1524 ), Besuki, E. Java, leg. J. Semmelink ; 1 male, 2 ov. females ( RMNH D 1077 ), Java, leg. P. Bleeker ; 2 males ( ZMA), Sg. Soenter [Sunter] at Batavia [Jakarta], Java ; SUMATRA: 3 males ( ZMA), streams at Kayutanam, W. Sumatra, leg. M. Weber ; BORNEO: 1 male ( ZRC 2000.2466 ), Sg. Belalong at Kuala Belalong , Temburong District, Brunei Darussalam, leg. K. K. P. Lim, 14–17.VI.1995 .

Type locality. Banten, Banten Province, Java, Indonesia .

Description. Mostly based on holotype. Rostrum short, 0.77 of cl (0.60–0.73 of cl in other specimens) with tip reaching or slightly short of distal end of scaphocerite, always extending beyond end of third segment of antennular peduncle; moderate, maximum depth equal to maximum dorsoventral diameter of cornea; lateral carina well developed, continuing almost to tip; dorsal carina slightly convex or straight with tip directed anteriorly or slightly curved upwards, teeth subequally spaced, those above orbit more closely spaced, armed with 10 teeth (9–11 in other specimens, mode 9 or 10), 3 teeth completely postorbital, postorbital teeth on anterior 0.33 of carapace (anterior 0.26–0.34 in other specimens); ventral carina with 3 teeth, first tooth located at about proximal half ( Fig. 1A ).

Carapace spinulate on branchiostegal and antero-dorsal regions in fully developed males. Ocular cornea well developed, 0.15 of cl (0.14–0.16 of cl in other specimens). Inferior orbital margin moderately produced, obtuse, postantennular carapace margin evenly rounded ( Fig. 1B ). Antennal spine sharp, slender, continuing posteriorly as ridge, situated below lower orbital angle; hepatic spine smaller, situated behind and below antennal spine; branchiostegal suture running from hepatic spine to carapace margin. Ocular beak well developed but without expanded lateral tip. Epistome completely bilobed, lobes with blunt rounded margins ( Fig. 1C ). Scaphocerite stout, 0.70 of cl (0.62–0.71 of cl in other specimens), length 3.30 times maximum width (3.12–3.55 in other specimens), lateral margin slightly concave, distolateral tooth failing to reach end of lamella. Third maxilliped with distal two-thirds of ultimate segment extending beyond antennal peduncle; ultimate shorter than penultimate segment, 0.87 times length of penultimate segment (0.79–0.82 times in other specimens); exopod as long as ischiomerus.

First pereiopods slender, chela extend beyond distal end of scaphocerite; fingers about as long as palm; carpus 2.09 times chela length (1.91–2.21 times in other specimens), 1.27 times merus length (1.19–1.28 in other specimens); few scattered short and medium stiff setae present on all segments otherwise glabrous ( Fig. 1I ).

Second pereiopods stout, rather long, similar in shape, unequal in size; distal half of minor cheliped carpus extends beyond end of scaphocerite. Spines on inner margin of chela, carpus, merus and ischium largest but less dense than those on other margins. Major cheliped ( Fig. 2A ): all segments covered with spines and few scattered short stiff setae, chela 1.78 of cl (1.13–1.99 of cl in other specimens), length 6.55 times width (5.99–8.77 times in other specimens), outer and inner margins slightly convex and slightly straight respectively, upper and lower margins rounded; palm subcylindrical, greater than maximum merus width, slightly compressed, width 1.20 times depth (1.15–1.31 times in other specimens); fingers 0.53 times palm length (0.49–0.54 times in other specimens), proximal two-thirds gaping, touching along distal one-third with a row of strong, sharp spines on each side of cutting edge of each finger, tips uncinate; dactylus with 2 large teeth, first tooth at proximal 0.61, second tooth at proximal 0.30 and 1 or 2 smaller teeth towards articulation of fingers, pollex with 2 large teeth, first tooth at proximal 0.51, second tooth at proximal 0.20 and 4 or 5 smaller teeth towards articulation of fingers, teeth unequally distributed along cutting edges; carpus 0.79 times palm length (0.61–0.83 times in other specimens), conically long, length 4.12 times distal width (2.87– 4.63 in other specimens), 0.52 times chela length (0.41–0.56 times in other specimens), 1.18 times merus length (1.03–1.12 times in other specimens); merus not inflated, 1.48 times ischium length (1.27–1.80 times in other specimens); ischium tapered. Minor cheliped ( Fig. 2B ): generally resembling major cheliped; spines and few scattered long stiff setae present on all segments; cheliped length 0.79 times major cheliped (0.81– 0.86 times in other specimens); fingers 0.63 times palm length (0.53–0.65 times in other specimens), not gaping with a row of sharp spines on each side cutting edge of each finger; dactylus with 3–7 small teeth, pollex with 5 or 6 small teeth, teeth subequaly distributed along proximal 0.30 of cutting edges; carpus shorter than chela, conically long, 0.93 times palm length (0.75–0.97 times in other specimens), 1.07 times merus length (1.02–1.15 times in other specimens); merus subcylindrical, 1.46 times ischium length (1.16–1.67 times in other specimens); ischium tapered.

Third pereiopods with tip of dactylus reaching distal border of scaphocerite; spinules abundant on propodus, few on carpus and distal merus, otherwise glabrous; few scattered moderate-length stiff setae present on all segments; dactylus stout, curved, fringed with dorsolateral setae, ventral carina poorly developed; propodus length 11.73 times longer than wide (9.33–11.31 times in other specimens); 15 ventral spines distributed along length of propodus, 2 distal most spines paired; carpus 0.51 times propodus length (0.54–0.56 times in other specimens); merus 1.05 times propodus length (1.12–1.16 in other specimens), 1.92 times ischium length (1.90–1.98 in other specimens) ( Figs. 1J–K ).

Fourth pereiopods with tip of dactylus reaching distal one-fifth of scaphocerite; spinules and few scattered moderate-length stiff setae present on all segments; 20 ventral spines distributed along length of propodus, 2 distal most spines paired; merus 1.94 times ischium length (1.84–1.93 times in other specimens).

Fifth pereiopods with tip of dactylus reaching distal two-fifths of scaphocerite; spinules few, scattered moderate-length stiff setae present on all segments; 19 ventral spines distributed along length of propodus; merus 0.91 as long as propodus (0.94–0.99 times in other specimens), 1.98 longer than ischium (1.76–1.94 times in other specimens).

T4 with small triangular median process, without posterior submedian plate ( Fig. 1D ); T8 with narrowly separated anterolateral lobes, without median process ( Fig. 1E ). Abdomen smooth, glabrous. First 2 male abdominal sternites with large, slender triangular median process of similar size and form; third abdominal sternite with small or without median process ( Fig. 1F ). Inter-uropodal sclerite well developed, elevated as longitudinal preanal carina, carina medium-sized, slightly larger than posterolateral teeth of sixth abdominal somite. Telson moderate, stout, glabrous, 4.66 times median width (3.50–4.06 times in other specimens), lateral margin straight, convergent, 2 pairs of dorsal spines present, posterior subventral margin straight with pointed median process, median projection overreached by inner pair of posterior spines ( Fig. 1H ). Uropods with acute distolateral tooth, mobile mesial spine as large as distolateral tooth ( Fig. 1G ); exopod 2.11 times longer than wide (1.91–2.11 times in other specimens). Developed eggs small, maximum size 0.8 x 0.5 mm, ovoid, numerous.

Remarks. De Man (1879) defined Palaemon javanicus Heller, 1862 , as a medium-sized species which has unequal and moderately long second pereiopods which are covered with spines, with the carpus conically long but shorter than the palm. He was certain that his specimens [1 male from Besuki, E. Java (RMNH D 1524) and 1 male and 2 ovigerous females from Java (RMNH D 1077)] were identical with Palaemon javanicus Heller, 1862 , since they were also collected from Java, although he noted that there are some differences, notably in the form of the second pereiopods. De Man (1879: 181), however, commented that Heller’s drawing was not accurate and dismissed the observed differences. De Man (1879) then re-described in detail the material from Java which he identified as P. javanicus , and this is the concept of the species most subsequent authors have followed.

In this study, the type material of P. javanicus Heller, 1862 (NHMW 7689), and the specimens from Java identified and re-described by De Man (1879) as " P. javanicus " were examined. The results show that they actually belong to two different species. Although Heller’s figure was somewhat schematic, it does show the important species characters and his description actually matches very well with his three type specimens of P. javanicus Heller, 1862 . De Man (1879) did not check the types of P. javanicus Heller, 1862 , and had incorrectly assumed that Heller’s (1862) figure was inaccurate. It is unfortunate that all subsequent crustacean workers did not check Heller’s types and unquestionably followed De Man’s (1879) definition of the species for more than 100 years. As the present study now shows, Palaemon javanicus Heller, 1862 , is actually conspecific and is a senior synonym of a well known forest species, M. trompii (De Man, 1898) , instead (see discussion later).

The differences between the two species are obvious: P.javanicus sensu De Man (1879) has a completely bilobed epistome (vs. partly bilobed in the types); a T4 with a small triangular median process (vs. without median process in the types); the anterior lobes of T8 are narrowly separated (vs. moderately separated in the types); the first two abdominal sternal median processes are large and slender (vs. large and broad in the types); the third to fifth periopods are spinulate (vs. glabrous in the types); both the second pereiopods are covered with spines and few scattered short stiff setae (vs. major chela densely covered with short velvety setae and minor chela covered with few scattered long stiff setae in the types) and the carpus is distinctly shorter than the palm (vs. equal in the types).

There can therefore be no doubt that the specimens attributed to M. javanicum by De Man (1879) and almost all subsequent workers since (e.g. Holthuis 1950; Johnson 1960; Wowor & Choy 2001) are not M. javanicum sensu stricto but belong to another as yet unnamed species. As no older name is available, we here propose to name this new species Macrobrachium duri spec. nov. A male specimen (MZB Cru 1079) from Banten, Banten Province, Java, Indonesia, is here selected as the holotype.

Macrobrachium duri spec. nov. closely resembles M. neglectum , but the differences between these two species have been discussed by Wowor & Choy (2001, as M. javanicum and M. neglectum ; see also Wowor et al. 2004). In this present study, some additional differences are noted. Macrobrachium duri spec. nov. can be further distinguished more from M. neglectum by the absence of posterior submedian plate of T4 (vs. present as a moderate prominent plate), glabrous first pereiopods (vs. spinulate), the proximal two-thirds of major second pereiopod fingers been gaping (vs. whole fingers); and the fingers of the second minor pereiopod touching along the cutting edges (vs. gaping).

Etymology. The specific name alludes to the form of its second pereiopods, which is covered by numerous spines. The name is derived from the Indonesian word for spiny, “duri”. The name is used as a noun in apposition.

Ecology. Macrobrachium duri spec. nov. occurs in large and small rivers in forested areas where the water is clean, clear and fast flowing. Wowor & Choy (2001) documented that their material was from a river about 1.5 m deep, with a sand-gravel-cobble-boulder substrate; the water quality being typical of a relatively unpolluted stream, with temperature between 24–25°C and pH 5.9–6.9.

Distribution. Java, West Sumatra and Brunei Darussalam at western Borneo.

Figures

FIGURE 1. Macrobrachium duri spec. nov., holotype male (cl 20.7, MZB Cru 1079): 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, H–J = 5.0 mm; E–F = 2.0 mm; B–D, G, K = 1.0 mm.

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.