Tenuipedium palaemonoides ( Holthuis, 1950 ) Holthuis, 1950

Tenuipedium palaemonoides ( Holthuis, 1950) View in CoL comb. nov.

( Figs. 4–6 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Macrobrachium palaemonoides Holthuis, 1950: 136 View in CoL , Fig. 31. — Chace & Bruce 1993: 34.

Material examined. Female, cl 5.7 ( RMNH D 5140, lectotype designated herein), Lake Laut Tawar (Luolo), Simalur, P. Simeulue, off Sumatra at Indian Ocean, leg. E. Jacobson, VIII.1913; paralectotypes ( RMNH D 53114), 26 juveniles (cl 1.5–2.4), 21 males (cl 2.8–3.8), 13 females (cl 2.6–5.7), 2 ov. females (cl 4.7), same data as lectotype.

Description (based on lectotype). Rostrum long, 1.26 of cl (1.41–1.54 in paralectotypes) with tip distinctly exceeding distal end of scaphocerite, basal crest poorly developed, low; slender, maximum depth distinctly less than maximum dorsoventral diameter of cornea; lateral carina well developed, continuing about proximal two-thirds; dorsal carina slightly convex above orbit with tip directed anteriorly or distal half curved upwards, teeth more closely spaced above orbit, wider towards distal with 1 or 2 subapical teeth, armed with 8 teeth (6–9 in paralectotypes, mode 8), 2 teeth completely postorbital (1 or 2 in paralectotypes, mode 2), postorbital teeth on anterior 0.18 of carapace (0.17–0.21 in paralectotypes); ventral carina with 6 teeth (6–8 in paralectotypes, mode 7), first tooth located at about proximal one-third ( Fig. 4 View FIGURE 4 A).

Carapace glabrous. Ocular cornea well developed, 0.26 times cl. Inferior orbital margin moderately produced, slightly angular, appearing truncated, postantennular carapace margin straight ( Fig. 4 View FIGURE 4 B). Antennal spine sharp, slender, continuing posteriorly as a ridge, situated below lower orbital angle; hepatic spine smaller, situated behind and below antennal spine; branchiostegal groove running below hepatic spine, from antennal carapace margin to some distance behind hepatic spine. Ocular beak well developed, but without expanded lateral tip. Epistome completely bilobed, lobes with rounded margin ( Fig. 4 View FIGURE 4 C). Scaphocerite slender, 0.89 of cl, length 3.29 times maximum width, lateral margin straight, distolateral tooth failing to reach end of lamella, anterior margin strongly produced forward at inner margin. Third maxilliped with ultimate segment extending beyond antennal peduncle; ultimate shorter than penultimate, 0.62 times as long as penultimate; exopod shorter than ischiomerus ( Fig. 6 View FIGURE 6 F).

First pereiopods slender, exceeding scaphocerite by half or whole length of fingers, shorter than second pereiopods; fingers about as long as palm; carpus 2.13 times chela length, 1.19 merus length; few scattered short stiff setae present on all segments ( Fig. 5 View FIGURE 5 A).

Second pereiopods similar in shape, equal in size, very slender; distal one-third of carpus extending beyond distal end of scaphocerite. Whole leg covered with few short stiff setae, otherwise glabrous. Chela 0.47 of cl, length 9.0 times width, outer and inner margins more or less straight, fingers slightly curve inwards, upper and lower margins rounded; palm greater than maximum merus width, subcylindrical; fingers 1.25 times palm length, touching along cutting edges, narrow at proximal, widest at distal three-quarters; dactylus and pollex without tooth; fingers uncinate at tip; carpus 4.25 times palm length, slightly tapered, length 17.0 times distal width, 1.89 times chela length; merus not inflated, 0.93 times ischium length; ischium not tapered ( Fig. 5 View FIGURE 5 B).

Third pereiopods with entire dactylus extending beyond distal end of scaphocerite, shorter than second pereiopods, but longer than first pereiopods; few scattered short stiff setae present on all segments, otherwise glabrous; dactylus slender, curved, fringed with dorsolateral setae, ventral carina obsolete; 9 ventral spines distributed along length of propodus ( Fig. 5 View FIGURE 5 C).

Fourth pereiopods with distal half or two-thirds of propodus extending beyond distal end of scaphocerite, longer than second pereiopods; few scattered short stiff setae present on all segments, otherwise glabrous; 10 ventral spines distributed along length of propodus ( Fig. 5 View FIGURE 5 D).

Fifth pereiopods with distal three-quarters of propodus extending beyond distal end of scaphocerite, longer than fourth pereiopods; few scattered short stiff setae present on all segments, otherwise glabrous; 6 ventral spines distributed along length of propodus ( Fig. 5 View FIGURE 5 E).

T4 with small triangular median process; with low posterior submedian plate ( Fig. 4 View FIGURE 4 D–E); T8 of male without anterolateral lobes, with low, wide median process ( Fig. 4 View FIGURE 4 F). Abdomen smooth, glabrous, fifth segment with bilobed posterolateral margin ( Fig. 4 View FIGURE 4 K). Male first abdominal sternite with small triangular median process; second and third abdominal sternites without median process ( Fig. 4 View FIGURE 4 G). Inter-uropodal sclerite not developed, preanal carina absent. Telson elongated, slender, glabrous, 5.80 times as long as median width, lateral margin straight, convergent, 2 pairs of dorsal spines present, posterior subventral margin straight with long median point, median projection overreached by inner pair of posterior spines, with 1 pair of long plumose subventral setae which are shorter than inner pair of spines ( Fig. 4 View FIGURE 4 I–J). Uropods with acute distolateral tooth, mobile mesial spine distinctly longer than distolateral tooth ( Fig. 4 View FIGURE 4 H); exopod 3.82 times longer than wide. Developed eggs medium-size, maximum size 0.7 × 0.5 mm, ovoid, not numerous.

Habitat. Freshwater lake.

Remarks. Tenuipedium palaemonoides comb. nov., was well described with excellent drawings by Holthuis (1950). The description was based on 63 specimens, including two ovigerous females from Pulau Simeuleu in Indonesia. So far, this species is known only from its type locality but its taxonomy was reviewed by Chace & Bruce (1993).

In 1974, Kamita recorded this species from Nepal. Although the specimens examined by Kamita (1974) are not available for this study, his description strongly suggests that these specimens are not T. palaemonoides . They have the fourth and the fifth pereiopods shorter than the second pereiopod (distinctly longer in T. palaemonoides ), and the eggs are 1.2 mm long and 1.0 mm wide (0.7 × 0.5 mm in T. palaemonoides ). The description of “ M. palaemonoides ” by Kamita (1974) suggests that it is Macrobrachium lamarrei lamarrei (H. Milne Edwards, 1837) instead. Both species have the tip of the rostrum extending beyond the distal end of the scaphocerite, the distal part of the rostrum curved upwards with only one subapical tooth, a gap between the subapical tooth and the rest of the dorsal teeth, the same rostral formula and the chela of the second pereiopod is more than half but less than three-quarters the length of the carpus.

Cai et al. (2004) previously commented that Kamita’s (1974) specimens of “ M. palaemonoides ” are probably conspecific with this species. Macrobrachium palaemonoides was also recorded from Thailand by Naiyanetr (1998). However, after re-examining these specimens, Cai et al. (2004) concluded that they are actually M.

lanchesteri (De Man, 1911). Naiyanetr (2007) continued using the incorrect name of M. palaemonoides for his material from Surin, North East Thailand.

Distribution. So far only known from the type locality.