Macrobrachium guizhouense Jiang & Chen, 2025

Jiang, Xuankong, Zhou, Jiajun, Ma, Kayan, Wang, Yaqin, Xie, Zhicai & Chen, Huiming, 2025, The cavernicolous freshwater prawn in China, with description of two new species (Decapoda, Palaemonidae, Macrobrachium), Zoosystematics and Evolution 101 (4), pp. 1531-1554 : 1531-1554

Macrobrachium guizhouense Jiang & Chen sp. nov.

Figs 8 , 9 , 10

Type materials.

Holotype: • male ( IBGAS - Dec-Pal- 493-1) (tl 52.1 mm, cl 14.5 mm, rl 7.2 mm), China, Guizhou Province, Libo County, Jiaou Town, Malai Village, Malai Cave , 25.2722°N, 107.6638°E, alt. 790 m, 9.VI.2023, Jiang X. K., Wu L. & Fan C. leg.

Paratypes: • 20 males ( IBGAS - Dec-Pal- 493-2 – 21) (tl 36.8–55.7 mm, cl 8.8–17.0 mm, rl 6.3–9.4 mm) and 44 females ( IBGAS - Dec-Pal- 493-22 – 65) (tl 31.5–61.7 mm, cl 7.8–20.8 mm, rl 5.3–9.8 mm), same data as holotype . • 1 male ( IBGAS - Dec-Pal- 494-1) (tl 50.1 mm, cl 11.6 mm, rl 9.2 mm) and 6 females ( IBGAS - Dec-Pal- 494-2 – 7) (tl 51.2–63.7 mm, cl 12.2–16.9 mm, rl 8.5–8.7 mm), Malai Cave , III.2023, Luo T. et al. leg . • 6 males ( IBGAS - Dec-Pal- 495-1 – 6) (tl 52.1–54.4 mm, cl 12.1–13.1 mm, rl 7.7–9.2 mm) and 8 females ( IBGAS - Dec-Pal- 495-7 – 14) (tl 43.4–61.5 mm, cl 10.7–17.4 mm, rl 6.4–7.8 mm), Malai Cave , 10.XI.2023, Liu Y. W. et al. leg . • 2 females ( IBGAS - Dec-Pal- 496-1 – 2) (tl 45.6–64.6 mm, cl 11.5–16.9 mm, rl 6.9–10.0 mm), Libo County, Jiaou Town, Gengzao Village, Gengzao Cave , 25.2735°N, 107.6777°E, alt. 775 m, 28.VI.2023, Zhou J. J. et al. leg . • 1 male ( IBGAS - Dec-Pal- 497-1) (tl 63.1 mm, cl 15.0 mm, rl 9.4 mm) and 1 female ( IBGAS - Dec-Pal- 497-2) (tl 61.7 mm, cl 16.7 mm, rl 7.6 mm), Gengzao Cave , 8.XI.2023, Jiang X. K. et al. leg .

Description.

Body moderately robust (Fig. 8 ). Rostrum (Figs 8 , 9 A ) reaching to end of scaphocerite, 0.4–0.7 times of cl, straight, or slightly upward distally. Dorsal margin with 8–11 teeth (mode 9), including 3–4 teeth behind orbit (mode 3), starting from about 1 / 3 of carapace length. Dorsal teeth equally space, or teeth more widely spaced on postorbital regions than on anterior. Ventral margin with 2–4 teeth (mode 3).

Eyes with cornea totally degenerated. Ocular peduncle small, elliptical and non-pigmented (Figs 8 , 9 A ).

Carapace smooth and glabrous. Antennal spine small, tip reaching anterolateral margin of carapace. Hepatic spine small, lying behind and below antennal spine (Figs 8 , 9 A ).

Abdomen smooth and glabrous. First to third pleurites broadly rounded, fourth and fifth pleurites slightly produced posteriorly. Sixth somite 1.4–1.7 times as long as fifth somite, with posteroventral angle slightly protruded (Figs 8 , 9 A ).

Telson 1.5 times length of sixth segment, 0.4–0.5 times of cl. Tapered posteriorly, with a sharp point. Dorsal surface with two pairs of small spines. Posterior margin bearing two pairs of lateral spines. Inner spines obviously longer than outer spines, with plumose setae between inner spines (Fig. 10 G ).

Antennule with sharp stylocerite, reaching about half of basal segment of antennular peduncle. Basal segment broad, about 1.5 times as wide as second segment, as long as wide; distolateral spine of basal antennular segment slender, reaching 0.4 times as long as second segment. Second segment as long as basal segment, ca. 1.2 times as long as distal segment. All segments except distal segment with submarginal plumose setae (Fig. 9 B ).

Scaphocerite about 2.2 times longer than wide. Inner margin somewhat convex; lateral margin strait, with stout distolateral tooth, not reaching anterior margin (Fig. 9 C ).

Mandible typical of genus, with three-segmented palp; three segments subequal in length; incisor process with three sharp teeth; molar process robust, truncate distally (Fig. 9 D ).

Maxillular palp deeply bilobed, upper lobe robust, longer than lower lobe, with few setae distally; lower lobe stout and small, devoid of setae with tip hook-like. Upper lacinia broadly elongated, distal margin with rows of strong spines, lower lacinia shorter than upper lacinia, tapering distally, densely setose (Fig. 9 E ).

Maxilla with simple palp; basal endite deeply bilobed, upper and lower lobes subequal and digitiform, with numerous simple setae distally; scaphognathite broad, about 4.7 times as long as wide (Fig. 9 F ).

First maxilliped with simple and small palp, basal and coxal endites distinct, tip of flagellum of exopod densely setose, epipod deeply bilobed (Fig. 9 G ).

Second maxilliped with 5 - segmented endopod, flagellum with numerous plumose setae distally, epipod simple, with developed podobranch (Fig. 9 H ).

Third maxilliped with robust endopod; antepenultimate with rows of simple setae on inner margin; penultimate 0.6 times length of antepenultimate, with rows of long, simple setae on inner and lateral margins; ultimate segment about 0.8 times penultimate segment, with rows of long, simple setae; exopod well-developed, reaching 0.7 times the length of antepenultimate, with plumose setae distally (Fig. 10 A ).

First pereiopod slender, reaching beyond end of scaphocerite by carpus. Ischium 0.5 times as long as merus; merus 0.9 times as long as carpus; carpus 1.8 times as long as chela; finger 1.3 times as long as palm (Fig. 10 B ).

Second pereiopod moderately robust, subequal in size, similar in both sexes. Merus 1.2 times as long as the ischium; carpus 0.9 times as long as merus, 1.4 times as long as palm; palm slightly inflated; finger 1.6 times as long as palm (Fig. 10 C, D ).

Third pereiopod slender, merus 2.3 times as long as carpus; carpus 0.5 times as long as propodus; propodus 2.7 times as long as dactylus with several small spines on ventral margin (Fig. 10 E ).

Fourth pereiopod longer than third pereiopod, similar in form.

Fifth pereiopod slenderer and longer than third. merus 1.7 times as long as carpus; carpus 0.5 times as long as propodus; propodus 4.8 times as long as dactylus, with several small spines on ventral margin; dactylus terminating in a small claw (Fig. 10 F ).

Male first pleopod with endopod about half length of exopod, inner margin concave, outer margin slightly convex.

Male second pleopod with well-developed appendix masculina bearing numerous spiniform setae. Appendix interna digitiform, reaching to 0.6 length of appendix masculina.

Uropodal diaeresis with inner movable spine shorter than outer angle.

Color.

Body semi-transparent to golden yellow, all appendages semi-transparent (Fig. 8 ).

Etymology.

This species is named after the type locality, highlighting that this is the first stygobitic Macrobrachium species found in Guizhou Province.

Distribution.

Libo County, Guizhou Province, China.

Habitat.

Malai Cave and Gengzao Cave have similar environments and are both located within a village. Both caves slope gently downward. About 300 meters from their entrances; each cave contains a large pool. Due to the obstruction by rocks, the exact area and depths of the pools are unclear. The substrates consist of silt and rocks. Local residents draw water from these pools for domestic use. Macrobrachium guizhouense sp. nov. were collected from these pools.

Remarks.

This species differs from all epigean species as well as M. parvum sp. nov. and M. tenuipes by the completely degraded somatic pigmentation and eyes. It can be separated from M. elegantum by the unicuspidate tip of rostrum (bifurcate in M. elegantum ), the broader scaphocerite (2.2 times longer than wide in M. guizhouense sp. nov. vs. 3.0 in M. elegantum ), the different rostral formula (3–4 + 5–7 / 3 – 4 in M. guizhouense sp. nov. vs. 3–4 + 3–4 / 4 – 6 in M. elegantum ) and the different ratios between the segments of second pereiopods. This species can be distinguished from M. duanense by the palm of second pereiopods which is shorter than ischium; from M. lingyunense by the relatively broader scaphocerite (2.2 times longer than wide in M. guizhouense sp. nov. vs. 2.4 in M. lingyunense ) (Table 4 ).

Figures

Figure 8. Live specimen of Macrobrachium guizhouense Jiang and Chen, sp. nov. (male, IBGAS - Dec-Pal- 493-3). A. Lateral view; B. Dorsal view.

Figure 9. Holotype of Macrobrachium guizhouense Jiang and Chen, sp. nov. (IBGAS - Dec-Pal- 493-1). A. Cephalothorax and cephalic appendages, lateral view; B. Antennule; C. Antenna; D. Mandible; E. Maxillule; F. Maxilla; G. First maxilliped; H. Second maxilliped. Scale bars: 5 mm (A); 2.5 mm (B, D – H); 5 mm (C).

Figure 10. Holotype of Macrobrachium guizhouense Jiang and Chen, sp. nov. (IBGAS - Dec-Pal- 493-1). A. Third maxilliped; B. First pereiopod; C. Second pereiopod; D. Chela of second pereiopod; E. Third pereiopod; F. Fifth pereiopod; G. Telson. Scale bars: 2.5 mm (A, B, G); 10 mm (C, D); 5 mm (E, F).