Macrobrachium ustulatum

Macrobrachium ustulatum (Nobili, 1899) Fig. 5, Table 2 P.[alaemon] (Eupalaemon) ustulatus Nobili, 1899: 241 (Rigo, SE Papua). Palaemon ustulatus – de Man 1915: 431, pl. 29, fig. 32 (Rigo, SE Papua). Material examined Holotype PAPUA NEW GUINEA: 1 ♂, Rigo District, 9.8767° S, 147.7938° E, unknown date, 23.5 mm CL (MSNG VII-106). Other material VANUATU: 1 ♂, Espiritu Santo Island, Ora Jourdain River, 15.1666° S, 166.8999° E, 3 Oct. 1994, 20.7 mm CL (MNHN-IU-2013-13201); 1 ♂, 22 mm CL (MNHN-IU-2013-13202). REPUBLIC OF PALAU: 1 ♂, Palau Island, Negmeskang River, 7.5413° N, 134.5778° E, 1 Mar. 2011, 20.7 mm CL (MNHN-IU-2013-13203). Description ROSTRUM. Moderately long, reaching end of scaphocerite (Fig. 5A); tip horizontal; dorsal margin nearly straight, faintly convex, with 10–12 teeth, including 3 teeth on carapace; ventral margin with 3–4 teeth; teeth large, generally evenly spaced, with gap near anterior end of dorsal series; sometimes distance between 1 st and 2 nd teeth larger than between 2 nd and 3 rd teeth. GENERAL CEPHALON. Eyes well developed; cornea as long as, but broader than peduncle; stylocerite distinctly pointed, reaching beyond basal segment; inferior orbit bluntly angular (Fig. 5A); postantennular carapace margin straight or slightly concave; protective setation absent on carapace; epistome lobes narrowly separated, strongly produced anteroventrally (Fig. 5B); TS4 with rounded median process (Fig. 5C). SECOND CHELIPEDS (fully developed ♂). Unequal sizes, non-isomorphic. Major P2 (Fig. 5D) long, subcylindrical, with small part of merus extending beyond scaphocerite; carpus 0.68–0.73 CHL, 1–1.12 PL. Fingers slender 0.46–0.58 PL; dactylus shorter than FF. Cutting edges (Fig. 5E) with 4–5 conical teeth (3 rd largest) followed by 6–10 evenly spaced, very small, blunt teeth, not along entire length; teeth diminishing in size distally; CEFF with teeth arrangement similar to that of dactylus; basally armed with ridge formed by 2 small teeth and 3–4 larger, conical teeth followed by 4–6 evenly spaced, small, blunt teeth, not along entire length; teeth diminishing in size distally. Largest tooth of FF lies just after largest tooth of CED when fingers closed. Cheliped with numerous spiniform setae, larger on inner edge, smaller and denser on outer edge. Numerous long setae present on manus and outer edge of fingers. Merus 0.54–0.61 CAL, ischium 0.64–0.85 MEL. Minor P2 (Fig. 5F) with entire carpus beyond scaphocerite. Carpus 0.67–0.75 CHL, 1.01–1.25 PL. Fingers slender 0.49–0.66 PL. CEFF with 11–14 teeth, gradually diminishing in size distally (Fig. 5G). CED with 13–15 teeth, slightly smaller and more numerous than those of major P2, similar teeth arrangement to that of dactylus. Fingers, palm and carpus densely packed with velvety setae. MEL 0.62–0.72 CAL, IL 0.74–1.05 MEL. ABDOMEN. Smooth, inter-uropodal sclerite with preanal carina. Distribution Syntopic with M. australe in the Northwest Pacific Ocean (Taiwan, Philippines, Papua New Guinea, Indonesia and Palau) and in the Southwest Pacific Ocean (Vanuatu) (Fig. 1). Habitat Lotic habitats in the middle course of rivers, clear and oxygenated waters, sometimes above waterfalls. Rocky substrates, boulders, pebbles and pools in countercurrents. Color patterns Body colors (Fig. 4B) tend to match the substrate, varying from black to brownish red, with three reddish stripes on each side of the cephalothorax. Remarks Some specimens originally assigned to P. dispar may correspond to M. ustulatum. This applies to de Man 1892: 435, pl. 26, fig. 44d (Salayar Island, Indonesia); de Man 1893: 304 (Flores, Indonesia); de Man 1902: 766 (Halmahera, Indonesia); and de Man 1915: 435, pl. 29, figs 14–14a (Papua New Guinea).

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