Macrobrachium kelianense, Wowor & Short, 2007

Wowor, Daisy & Short, John W., 2007, Two New Freshwater Prawns Of The Genus Macrobrachium Bate, 1868 (Crustacea: Decapoda: Palaemonidae) From The Kelian River, East Kalimantan, Indonesia, Raffles Bulletin of Zoology 55 (1), pp. 77-87 : 82-86

Macrobrachium kelianense , new species

( Figs 3 , 4 )

Macrobrachium pilimanus – Holthuis, 1950: 214 (part); Johnson, 1960: 263 (part); 1963: 10 (part); Chace & Bruce, 1993: 35 (part) (not Palaemon pilimanus de Man, 1879 ).

Material examined. – Holotype: male (11.2 mm CL) (MZB Cru 1477), Sg. Kelian confluence with Sg. Ketang, Mahakam River basin, E. Kalimantan, coll. R. & J. Powell, 2 Nov.1995.

Paratypes: 6 males (9.5–11.6 mm CL) , 3 females (7.9–9.4 mm CL), 8 ovigerous females (9.5–10.6 mm CL) (QM W21515), same data as holotype; 1 ovigerous female (10.3 mm CL) (MZB Cru 1478), same data as holotype ; 1 male (8.2 mm CL) ( ZRC 2000.2489 ), Sg. Kelian, Mahakam River basin, E. Kalimantan, coll. C. Yule, Sep. 1990 ; 1 female (9.4 mm CL) ( ZRC 2000.2490 ), Sg. Kelian, Mahakam River basin, E. Kalimantan, coll. C. Yule, Sep. 1991 .

Others: Mahakam basin: 7 juveniles, 40 males, 51 females, 8 ovigerous females (MZB Cru 1563), Sg. Lakan at Lakan Bilem village, coll. D. Wowor, 9–10 Jun.2006; 1 male (MZB Cru 1564), Sg. Mapan at Jantur Mapan, Bigung village, coll. D. Wowor, 10 Jun.2006.

Diagnosis. – A subcylindrical body form species. Rostrum short, reaching slightly behind or end of third segment of antennular peduncle; slender; dorsal carina slightly convex. Rostral formula: 3–5) 12–17/ 2–3 teeth. Inferior orbital margin moderately produced, obtuse, postantennular carapace margin evenly rounded. Carapace glabrous. Ocular beak moderately developed. Epistome completely trilobed. Second pereiopod robust, similar in shape, unequal in size. Long velvety setae present on both chelae. Fingers with more than 10 teeth. Carpus conical, shorter than chela, palm and merus. All segments covered with spinules. T4 unarmed, with moderate posterior submedian plate; T5 with transverse plate with median notch; T8 with moderately separated anterior lobes, without median process posteriorly. Preanal carina present. Telson relatively slender, glabrous, with about 6–9 pairs of long plumose subventral setae. Uropod glabrous; exopod with mobile mesial spine shorter than distolateral tooth. Developed eggs large, maximum size 1.7 by 1.2 mm, ovoid, few.

Description in holotype. – Rostrum. Short, 0.54 CL (0.53– 0.64 in paratypes), slightly behind or reaching end of third segment of antennular peduncle; slender, maximum depth distinctly less than maximum dorsoventral diameter of cornea; lateral carina well developed, continuing almost to tip; dorsal carina slightly convex, bent downwards in front of orbit with tip directed anteriorly, teeth subequally distributed, armed with 14 teeth (12–17, mode 14), 4 teeth (3–5, mode 4) completely postorbital, postorbital teeth on anterior 0.34 of carapace (0.28–0.35); ventral carina with 2 teeth (2 or 3, mode 2), first tooth located at about distal one-third ( Fig. 3A ).

General cephalon. Ocular cornea well-developed, 0.22 CL (0.21–0.25). Inferior orbital margin moderately produced, obtuse, postantennular carapace margin evenly rounded ( Fig. 3B ). 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. Carapace glabrous. Ocular beak moderately developed, without laterally expanded tip. Epistome completely trilobed, lobes with blunt rounded margin ( Fig. 3C ). Scaphocerite stout, 0.66 CL (0.58–0.71), length 2.96 times maximum breadth (2.70–3.08), lateral margin straight, distolateral tooth failing to reach end of lamella. Third maxilliped exceeding antennal peduncle by ultimate and distal one-third of penultimate; ultimate shorter than penultimate, 0.80 as long as penultimate (0.68–0.87); exopod shorter than ischiomerus.

First pereiopods. Slender, exceeding scaphocerite by chela and distal four-fifths of carpus; fingers about as long as palm; carpus 1.59 chela length (1.46–1.91), 1.19 merus length (1.12–1.42); few scattered short stiff setae present on all segments, otherwise glabrous ( Fig. 3I ).

Second pereiopods. Similar in shape, unequal in size, robust; carpus of minor cheliped extend beyond distal end of scaphocerite. Major cheliped. Spinules present only on proximal palm, carpus, distal merus and small part of inner margin of merus; fingers and distal part of palm lightly covered by tufts of long velvety seta; chela 1.58 CL (1.17– 1.51), length 4.77 times width (4.31–5.94), outer and inner margins slightly convex and concave respectively, upper and lower margins rounded; palm subcylindrical, clearly greater than maximum merus width, slightly compressed, width 1.25 times depth (1.19–1.21); fingers 1.39 times palm length (0.81–1.33), more or less touching along their length; dactylus with 16 medium-sized teeth and pollex with 11 medium-sized and 4 small teeth towards articulation of fingers, teeth subequally distributed along cutting edges; fingers uncinate at tip; carpus 0.58 palm length (0.44–0.77), conical, length 1.59 times distal width (1.70–2.46), 0.24 times chela length (0.24–0.30), 0.48 merus length (0.47–0.55), without tuft of velvety setae nor long stiff setae on distal margin; merus moderately inflated, length 3.10 times depth (2.89–4.61), 2.0 times ischium length (1.86–2.23); ischium tapered ( Fig. 4A ). Minor cheliped. Generally resembling major cheliped; few spinules present on palm, carpus and merus; palm covered lightly by scattered long stiff setae; fingers covered by tufts of long velvety setae; cheliped 0.71 times major cheliped (0.75–0.76); fingers 1.57 times palm length (1.24–1.59), more or less touching along their length; dactylus with 8 small teeth, pollex with 9small teeth, teeth subequally distributed at about proximal half; carpus shorter than chela, conical, 0.72 times palm length (0.70–0.79) and 0. 48 merus length (0.54–0.57), without tufts of long velvety setae on inner distal margin; merus subcylindrical and stout, 1.65 times ischium length (1.39–1.82); ischium shorter than merus, tapered ( Fig. 4B ).

Third pereiopods. Tip of dactylus reaching distal end of scaphocerite; few scattered short stiff setae present on all segments, otherwise glabrous ( Fig. 3J ); dactylus stout, curved, ventral carina obsolete ( Fig. 3K ); propodus length 9.20 times longer than width (9.25–13.33); 7 ventral spines distributed along length of propodus, 2 distal most spines paired; carpus 0.54 times propodus length (0.50–0.57); merus 1.26 times propodus length (1.14–1.30), 2.07 times ischium length (1.93– 2.15).

Fourth pereiopods. Tip of dactylus reaching distal end of scaphocerite; few scattered short stiff setae present on all segments, otherwise glabrous; 7 ventral spines distributed along length of propodus, 2 distal most spines paired; merus 2.23 times ischium length (1.86–2.40).

Fifth pereiopods. Tip of dactylus reaching distal one-eighth of scaphocerite; few scattered short stiff setae present on all segments, otherwise glabrous; 5 ventral spines distributed along length of propodus; merus 1.12 as long as propodus (0.98–1.12), 2.15 longer than ischium (1.96–2.30).

Thoracic sternum. T4 without median process; posterior submedian plate moderate with bluntly rounded tip, notch shallow and wide ( Fig. 3D ); T8 with anterior lobes moderately separated, without median process ( Fig. 3E ). Abdomen. Smooth, glabrous. Male abdominal sternites. First 2 abdominal sternites each with a small triangular median process of similar form and size, third abdominal sternite without a median process ( Fig. 3F ). Inter-uropodal sclerite. Well developed, elevated as longitudinal preanal carina, carina small-sized, smaller than posterolateral teeth of sixth abdominal somite. Telson . Relatively slender, glabrous, 4.23 times median width (3.61–4.73), lateral margin straight, convergent, 2 pairs of dorsal spines present, posterior subventral margin straight with rounded median point, median projection overreached by inner pair of posterior spines ( Fig. 3H ). Uropods. With acute distolateral tooth, mobile mesial spine distinctly smaller than distolateral tooth ( Fig. 3G ), exopod 2.95 times longer than broad (2.29–2.62), glabrous.

Etymology. – This species is named after its type locality, Kelian River.

Size. – Males reach larger sizes than females; the largest male recorded being 11.6 mm CL; the largest female 10.6 mm CL and ovigerous females are between 9.5 to 10.6 mm CL (n=9).

Remarks. – Macrobrachium kelianense , new species, closely resembles M. pygmaeum ( Roux, 1928) and M. eriocheirum Dai, 1984 , two members of M. pilimanus species group. The three species mentioned above have short rostrum which is not extending beyond the end of the third segment of the antennular peduncle, the chelae of the second pereiopods being slender with more than 10 teeth on each finger, the carpus being long conical, and the merus being slightly inflated. However, M. kelianense can be distinguished from M. pygmaeum in having a longer rostrum (ratio of rostrum length to carapace length 0.53–0.55 vs. 0.41–0.44); slightly more widely distributed postorbital teeth (ratio of epigastric length to carapace length 0.28–0.35 vs. 0.20–0.25); trilobed epistome (vs. partly bilobed); moderately separated T8 anterior lobes (vs. narrowly separated); more slender third periopods (ratio of propodus length to propodus width 9.20– 13.33 vs. 8.75–9.00); the first two abdominal sternites each with a small median process (vs. medium-sized); and a small preanal carina (vs. medium-sized).

Macrobrachium kelianense can also be separated from M. eriocheirum Dai, 1984 , by its longer rostrum (ratio of rostrum length to carapace length 0.53–0.55 vs. 0.41–0.49); trilobed epistome (vs. unilobed); moderately separated T8 anterior lobes (vs. narrowly separated); major second periopod with moderately inflated merus (vs. slightly inflated); more slender third periopods (ratio of propodus length to propodus width 9.20–13.33 vs. 8.13); the first two abdominal sternites each with a small median process (vs. medium-sized), the third abdominal sternite being without a median process (vs. small); and a small preanal carina (vs. medium-sized).

Distribution. – Mahakam River basin, E. Kalimantan Province, Borneo.

Comparative material examined. – Macrobrachium pygmaeum : 17 juveniles, 12 males, 4 females (ZMA De 240495), Kastoba crater lake, P. Bawean, E. Java, coll. J. H. Coert, 25–27 Nov.1937; 12 males (MZB Cru 278), P. Bawean, E. Java, coll. Asman, 17 Jun.1954. M. eriocheirum : holotype, male 17.75 mm CL ( IZAS), Jingsan , Yunnan, China, coll. C. Wang, 11 Apr.1957; paratypes , 1 male, 1

female (IZAS 00409), same locality as holotype, no date.

Figures

Fig. 3. Macrobrachium kelianense, new species, holotype, male 11.20 mm CL, MZB Cru 1477: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. Scale bars: A, I–J = 5 mm; E = 2 mm; B–D, F–H, K = 1 mm.

Fig. 4. Macrobrachium kelianense, new species, holotype, male 11.20 mm CL, MZB Cru 1477: A, dorsal view of major second pereiopod; B, dorsal view of minor second pereiopod. Setae omitted. Scale bar: A–B = 2 mm.