Macrobrachium tenuipes Zhu 2020

Macrobrachium tenuipes Zhu et al., 2020 Macrobrachium tenuipes Zhu et al., 2020: 512, figs 5–7, 8 A, C. Type locality: a cave in Mashan County, Guangxi, China. Material examined. • 2 males (IBGAS - Dec-Pal- 488-1 – 2) (tl 38.1–39.8 mm, cl 7.9–9.0 mm, rl 6.7–7.8 mm) and 1 female (IBGAS - Dec-Pal- 488-3) (tl 38.7 mm, cl 8.6 mm, rl 7.9 mm), Du’an County, Gaoling Town, Nongchitianchuan Cave, 24.0887°N, 108.0640°E, 10.IV.2024, Zhou J. J. leg. • 1 male (IBGAS - Dec-Pal- 489-1) (tl 47.0 mm, cl 10.6 mm, rl 8.4 mm) and 3 females (IBGAS - Dec-Pal- 489-2 – 4) (tl 47.0– 77.2 mm, cl 10.9–19.6 mm, rl 9.2–13.6 mm), Guangxi, Du’an County, Gaoling Town, Nongchitianchuan Cave, 13.IV.2024, Zhou JJ. leg. Diagnosis. Body yellowish, all appendages generally translucent to faint yellow. Carapace and abdomen smooth and glabrous. Rostrum slender, slightly convex above orbital margin, 0.8–1.1 times of cl, overreaching scaphocerite. Dorsal margin with 11–12 teeth, including 3 or 4 teeth behind orbit. Dorsal teeth placed more widely on anterior part. Ventral margin with 3 or 4 teeth. Eyes well-developed. Scaphocerite about 4.1 times longer than wide. Second pereiopod slender, subequal in size, similar in both sexes. Merus 1.1–1.2 times as long as ischium; carpus 1.2–1.3 times as long as merus, 1.1 times as long as palm; palm not inflated; finger 0.8–0.9 times as long as palm. Uropodal diaeresis with inner movable spine slightly longer than outer angle. Distribution. Mashan County and Du’an County, Guangxi, China. Habitat. The species was discovered in a karst window (a sinkhole in karst landscapes) of an underground river, which has an area of approximately 9,200 m 2 and a depth exceeding 60 m. Remarks. The COI genetic distance of the collected specimens ranges from 0–1.30 % compared to the type specimens (A 42 and A 49, see Table 2) and are morphologically consistent with the original description. This species can be distinguished from other cave-dwelling species by the obviously pigmented body and eyes (Table 4). As for its differences from epigean species, see Zhu et al. (2020). The type locality of this species is in Mashan County (Zhu et al. 2020). With the discovery of this species in Du’an, its distribution range has been extended to the northwest by about 50 km. The genetic differentiation between populations of these two sites is insignificant, and they cluster with the epigean species in the phylogram. This may further suggest that this species is a stygophile, having recently migrated to caves. It probably has a wider distribution range in the surface environment, which enables gene exchange between different cave populations.