Macrobrachium parvum Jiang & Zhou, 2025
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publication ID |
https://doi.org/10.3897/zse.101.154936 |
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publication LSID |
lsid:zoobank.org:pub:97B1649F-38E2-48F1-87A0-51A962FA17FA |
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DOI |
https://doi.org/10.5281/zenodo.16928280 |
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persistent identifier |
https://treatment.plazi.org/id/1119FDB1-D215-5CE8-B439-F630422D723B |
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scientific name |
Macrobrachium parvum Jiang & Zhou |
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sp. nov. |
Macrobrachium parvum Jiang & Zhou sp. nov.
Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4
Type materials.
Holotype: • male ( IBGAS - Dec-Pal- 484-1) (tl 41 mm, cl 9.6 mm, rl 7.1 mm), China, Guangxi, Du’an County, Baoan Town, Nonglitun Cave , 24.0791°N, 107.8840°E, 10.IV.2024, Zhou J. J. leg. GoogleMaps
Paratypes: • 6 males ( IBGAS - Dec-Pal- 484-2 – 7) (tl 30.2–36.8 mm, cl 7.8–9.0 mm, rl 5.6–7.4 mm) and 15 females ( IBGAS - Dec-Pal- 484-8 – 22) (tl 31.7–41.4 mm, cl 7.5–11.4 mm, rl 6.0– 7.6 mm), same data as holotype GoogleMaps ; • 2 males ( IBGAS - Dec-Pal- 485-1 – 2) (tl 39.6–44.0 mm, cl 9.4–10.2 mm, rl 6.6–8.5 mm) and 3 females ( IBGAS - Dec-Pal- 485-3 – 5) (tl 31.4–46.5 mm, cl 8.2–11.4 mm, rl 5.7–7.8 mm), Du’an County, Baoan Town, Nonglitun Cave , 11.IV.2024, Zhou J. J. leg ; • 1 male ( IBGAS - Dec-Pal- 486-1) (tl 37.1 mm, cl 9.7 mm, rl 5.8 mm) and 12 females ( IBGAS - Dec-Pal- 486-2 – 13) (tl 26.5–48.3 mm, cl 6.8–12.7 mm, rl 4.1–7.0 mm), Guangxi, Du’an, Gaoling Town, Nongguangshang Cave , 24.0095°N, 108.0823°E, alt. 198 m, 16.IV.2023, Zhou J. J. leg. GoogleMaps 2 females ( IBGAS - Dec-Pal- 487-1 – 2) (tl 36.0– 53.4 mm, cl 8.7–13.8 mm, rl 5.5–8.9 mm), Du’an County, Disu Town, Xiaodiao Village, Shuiyuandi Cave , 24.0061°N, 107.9840°E, 10.IV.2024, Zhou J. J. leg. GoogleMaps
Diagnosis.
Body semi-transparent to yellowish with ochreous marks on surface of carapace and abdomen, all appendages semi-transparent. Carapace and abdomen smooth and glabrous. Rostrum slender, reaching end of scaphocerite, 0.5–0.8 times of cl, straight, or slightly upward. Dorsal margin with 5–10 teeth, including 2–4 teeth behind orbit, starting from about 1 / 3 of carapace length. Dorsal teeth equally spaced, anterior part of rostrum without or only with one tooth. Ventral margin with 2–5 teeth (mode 4). Eyes with cornea strongly degenerated, only small area on tip pigmented. Ocular peduncle small and elliptical. Scaphocerite about 3.0 times longer than wide. Second pereiopod slender, subequal in size and similar for both sexes. Ischium 0.9 times as long as merus; merus 0.8 times as long as carpus; carpus as long as chela; finger 1.6 times as long as palm, palm not inflated. Uropodal diaeresis with inner movable spine subequal to outer angle.
Description.
Body slender (Fig. 2 View Figure 2 ). Rostrum slender, reaching end of scaphocerite, 0.5–0.8 times of cl, straight, or slightly upward distally. Dorsal margin with 5–10 teeth, including 2–4 teeth behind orbit, starting from about 1 / 3 of carapace length. Dorsal teeth equally spaced, anterior part of rostrum without or only with one tooth. Ventral margin with 2–5 teeth (mode 4) (Figs 2 View Figure 2 , 3 A View Figure 3 ).
Eyes with cornea strongly degenerated, only small area on tip pigmented. Ocular peduncle small and elliptical (Figs 2 View Figure 2 , 3 A View Figure 3 ).
Carapace smooth and glabrous. Antennal spine small, tip overreaching anterolateral margin of carapace. Hepatic spine small, lying behind and below antennal spine (Figs 2 View Figure 2 , 3 A View Figure 3 ).
Abdomen smooth and glabrous. First to third pleurites broadly rounded, fourth and fifth pleurites slightly produced posteriorly. Sixth somite 1.4–1.9 times as long as fifth somite, with posteroventral angle slightly protruded in a sharp tip.
Telson 1.4–1.5 times length of sixth segment, 0.5–0.6 times of cl. Tapered posteriorly, with a sharp point. Dorsal surface with two pairs of spines. Posterior margin bearing two pairs of lateral spines. Inner spines obviously longer than outer spines, with plumose setae between inner spines (Fig. 4 I View Figure 4 ).
Antennule with stout stylocerite, reaching about 1 / 4 length of basal segment of antennular peduncle. Basal segment broad, about 1.8 times as wide as second segment, as long as wide; distolateral spine of basal antennular segment small, reaching about 1 / 3 length of second segment. Second segment ca. 0.8 times as long as basal segment, ca. 0.9 times as long as distal segment. All segments except distal segment with submarginal plumose setae (Fig. 3 B View Figure 3 ).
Scaphocerite about 3.0 times longer than wide. Inner margin somewhat convex; lateral margin strait, with sharp distolateral tooth, not reaching anterior margin (Fig. 3 C View Figure 3 ).
Mandible typical of genus, with three-segmented palp of subequal length; incisor process with three sharp teeth; molar process robust, truncate distally (Fig. 3 D View Figure 3 ).
Maxillular palp bilobed, upper lobe slender, digitiform, slightly longer than lower lobe, with few setae distally; lower lobe stout and small. Upper lacinia broadly elongated, distal margin with rows of strong spines, lower lacinia shorter than upper lacinia, tapering distally, densely setose (Fig. 3 E View Figure 3 ).
Maxilla with simple palp; basal endite deeply bilobed, upper and lower lobes subequal and digitiform, with numerous simple setae distally; scaphognathite broad, about 3.7 times as long as wide (Fig. 3 F View Figure 3 ).
First maxilliped with simple and small palp, basal and coxal endites distinct, tip of flagellum of exopod densely setose, epipod deeply bilobed (Fig. 3 G View Figure 3 ).
Second maxilliped with 5 - segmented endopod, flagellum with numerous plumose setae distally, epipod simple, with developed podobranch (Fig. 3 H View Figure 3 ).
Third maxilliped with robust endopod; antepenultimate with row of simple setae on inner margin; penultimate 0.7 times length of antepenultimate, with rows of long, simple setae on inner margin; ultimate segment about 0.9 times penultimate segment, with rows of long, simple setae on inner and outer margins; exopod well-developed, reaching 0.7 times the length of antepenultimate, with plumose setae distally (Fig. 4 A View Figure 4 ).
First pereiopod slender, reaching beyond end of scaphocerite. Ischium 0.6 times as long as merus; merus 0.8 times as long as carpus; carpus 2.7 times as long as chela; finger 1.2 times as long as palm (Fig. 4 B, C View Figure 4 ).
Second pereiopod slender, subequal in size and similar for both sexes. Ischium 0.9 times as long as merus; merus 0.8 times as long as carpus; carpus as long as chela; finger 1.6 times as long as palm, palm not inflated (Fig. 4 D, E View Figure 4 ).
Third pereiopod slender, merus 1.4 times as long as carpus; carpus 0.7 times as long as propodus; propodus 5.3 times as long as dactylus (Fig. 4 F View Figure 4 ).
Fourth pereiopod longer than third pereiopod, generally similar in form (Fig. 4 G View Figure 4 ).
Fifth pereiopod slenderer and longer than third. Merus 1.4 times as long as carpus; carpus 0.7 times as long as propodus; propodus 7.0 times as long as dactylus; dactylus terminating in a small claw (Fig. 4 H View Figure 4 ).
Male first pleopod with endopod about 1 / 3 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 0.7 length of appendix masculina.
Uropodal diaeresis with inner movable spine subequal to outer angle.
Color.
Body semi-transparent to yellowish with ochreous marks on surface of carapace and abdomen, all appendages semi-transparent (Fig. 2 View Figure 2 ).
Etymology.
The specific name is a Latin word meaning “ little ” referring to the relatively small body size of the species.
Distribution.
Du’an County, Guangxi, China.
Habitat.
The interior spaces of Nonglitun Cave and Shuiyuandi Cave are spacious, with broad pools located approximately 50–100 meters from the entrances. The substrates of these pools consist of silt and rocks. Nongguangshang Cave is a section of an underground river, with numerous puddles about 50 meters from the entrance during the dry season. Macrobrachium parvum sp. nov. were discovered in these puddles. During the rainy season, the water levels in these three caves rise significantly, even overflowing the cave entrances to form small lakes.
Remarks.
This species exhibits significant morphological and molecular divergence from other cave-dwelling congeners. Key diagnostic traits include a smaller body size, extremely slender appendages, and the presence of degenerated yet traceable body color and eyes. It can be distinguished from all epigean species and M. tenuipes by the strongly reduced eyes with only small area in tip pigmented and the semi-transparent body color. This species differs from other four stygobiotic species in China by the pigmented eyes and body surface, the relatively smaller body size, the slender scaphocerite, and the extremely slender pereiopods, the shorter chela of second pereiopods and the moveable spine on uropodal diaeresis that are subequal to outer angle (Table 4 View Table 4 ).
Genetically, it demonstrates substantial interspecific divergence, with pairwise COI and 16 S sequence differences exceeding 23 % and 8 %, respectively. Phylogenetic analyses recover this taxon as a distinct evolutionary lineage. These combined morphological and molecular data robustly support its identity as a valid species.
The stygomorphic characteristics of this species indicate substantial adaptation to cave environments. However, the persistence of residual pigmentation and ocular structures suggest an incomplete transition to complete cave adaptation. We therefore classify it as a stygophile rather than a stygobite.
In Nongguangshang Cave and Shuiyuandi Cave, this species is inhabiting sympatrically with M. duanense .
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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