Caridina qiongzhongensis Hou, Zhang & Guo, 2025

Hou, Junjie, Zhang, Jiping, Chen, Bing, Zhang, Yixuan, Chen, Wenjian & Guo, Zhaoliang, 2025, Integrative taxonomy reveals the Caridina clinata Cai, Nguyen & Ng, 1999 species complex (Crustacea, Decapoda, Atyidae), with descriptions of eight new species from Hainan Island, China, Zoosystematics and Evolution 101 (4), pp. 2295-2336 : 2295-2336

Caridina qiongzhongensis Hou, Zhang & Guo sp. nov.

Figs 2 D , 9 , 10

Materials examined.

China – Hainan Island • Holotype: 1 ♂, cl 3.7 mm, ( FU 5727015 ), Qiongzhong County, 19°1'26"N, 109°50'27"E, al. 312 m, stn. 6, coll. WANG C. Y. and HOU J. J, 23 Jan. 2024 .

Paratypes: 1 ♂, cl 3.5 mm, ( FU 5727016 ); 1 ♂, cl 4.2 mm, ( FU 5727017 ); 1 ♂, cl 4.0 mm, ( FU 5727020 ); 1 ovigerous ♀, cl 5.0 mm, ( FU 5727018 ); 1 ♀, cl 4.6 mm, ( FU 5727019 ), same collection data as holotype . 1 ♂, cl 4.6 mm, ( FU 5727021 ); 2 ♀♀, cl 4.4–5.0 mm, ( FU 5727022 ), Qiongzhong County, 19°1'56"N, 109°47'26"E, al. 336 m, stn. 7, coll. YU W. D. and HOU J. J., 23 Jan. 2024 .

Comparative material.

Caridina serrata Stimpson, 1860 . China – Guangdong Prov. • 3 ♂♂, cl 3.2–3.8 mm, ( FU 5190001 ), Guishan Island , Zhuhai City, coll. Guo Z. L., 27 Nov. 2023.

Description.

Body (Fig. 2 D ): Small, slender and sub-cylindrical, males up to 4.6 mm cl, females up to 5.0 mm cl. Sixth abdominal somite 0.45–0.52 times as long as carapace.

Rostrum (Fig. 9 A, B ): Short, straight, reaching to the end of the first segment to the middle of 2 rd segment of antennular peduncle; 0.2–0.4 of cl; armed dorsally with 8–12 teeth, including 2–5 on carapace posterior to orbital margin, ventrally with 0–2 teeth; rostral formula 2–5 + 6 – 7 / 0 – 2; lateral carina dividing rostrum into two unequal parts, continuing posteriorly to orbital margin.

Eyes (Fig. 9 A, B ): Well-developed, on short ocular peduncle, cornea globular.

Carapace (Fig. 9 A, B ): Smooth, glabrous; antennal spine acute, fused with inferior orbital angle; pterygostomian margin broadly rectangular, slightly produced forward; pterygostomian spine absent.

Antennule (Fig. 9 C ): Stylocerite reaching 1.05–1.26 times as long as basal segment of antennular peduncle; basal segment as long or shorter than combined length of second and third segments, 1.48–1.63 times as long as second segment; second segment 1.70–2.01 times as long as third segments; all segments with marginal plumose setae.

Antenna (Fig. 9 D ): Scaphocerite 3.7 times as long as wide, outer margin straight, asetose, ending in a strong sub-apical spine, inner and anterior margins with long plumose setae.

First maxilliped (Fig. 9 H ): Palp of first maxilliped broadly triangular, ending in finger-like projection.

Third maxilliped (Fig. 10 B ): Basal segment 0.95–1.26 times as long as penultimate segment; penultimate segment 0.96–1.15 times as long as distal segment, ending in a large claw-like spine surrounded by simple setae, preceded by 5–6 thin spines on distal third of posterior margin, proximally a clump of long and short simple, serrate setae; exopod reaching beyond the beginning of second segment, distal margin with long plumose setae.

First pereiopod (Fig. 10 C ): Chela 2.06–2.25 times as long as high, 1.34–1.51 times as long as carpus; movable finger 2.58–3.32 times as long as wide and 0.87–1.16 times as long as palm, setal brushes well-developed; carpus 1.18–1.66 times as long as wide, slightly excavated distally; merus 0.95–1.44 times as long as carpus.

Second pereiopod (Fig. 10 D ): Chela 2.38–2.90 times as long as high, 0.83–0.90 times as long as carpus; movable finger 3.54–4.51 times as long as wide and 1.13–1.53 times as long as palm, setal brushes well-developed; carpus 4.13–4.90 times as long as wide, slightly excavated distally; merus 0.95–1.12 times as long as carpus.

Third pereiopod (Fig. 10 E ): Dactylus 2.88–4.03 times as long as wide, terminating in a prominent claw-like spine surrounded by simple setae, followed by 5–6 spiniform setae; propodus 2.88–4.51 times as long as dactylus, 8.72–10.61 times as long as wide; carpus 0.61–0.87 times as long as propodus; merus 1.76–2.16 times as long as carpus, with 3–4 spiniform setae on the posterior margin. Ischium sometimes with 1 small movable spiniform setae on the posterior margin.

Fourth pereiopod: Proportion and spination similar to third pereiopod.

Fifth pereiopod (Fig. 10 F ): Dactylus 3.22–4.70 times as long as wide, ending in prominent claw-like spine surrounded by simple setae, followed by a row of 35–52 spiniform setae; propodus 3.02–4.94 times as long as dactylus, 9.38–12.47 times as long as wide; carpus 0.43–0.67 times as long as propodus; merus 1.41–1.55 times as long as carpus, with 2–3 spiniform setae on the posterior margin. Ischium sometimes with 1 spine on the posterior margin.

First four pereiopods with epipod.

First pleopod (Fig. 10 G ): Endopod in male 0.50–0.56 times as long as exopod, oblong-reniform, distal end is distinctly narrower than the basal part, 2.77–3.09 times as long as wide, tip rounded, inner margin slightly concave. Outer margin slightly convex, long pappose setae on outer and distal margins, medium-length setae on inner margin; appendix interna well developed, arising from distal 0.25–0.33 of endopod, reaching slightly beyond end of endopod, distally with cincinuli.

Second pleopod (Fig. 10 H ): Appendix masculina rod-shaped, wider and slightly swollen in the end, reaching 0.68–0.69 length of exopod, some short spiny setae on basal part, the spiniform setae at the end of appendix masculina are thicker, and the spiniform setae of middle of appendix masculina are shorter; appendix interna well developed, reaching 0.50–0.56 of appendix masculina, distally with cincinuli.

Telson (Fig. 10 I ): With 5 pairs of short spiniform setae dorsally and one pair of short spiniform setae dorsolaterally; posterior margin with 4 pairs of intermedial spiniform setae, the innermost one usually strongest and longest. Exopodite of the uropod (Fig. 10 I ) bears a series of 20–23 movable spinules along diaresis.

Eggs: 0.70–0.76 mm × 1.17–1.30 mm in diameter.

Remarks.

Regarding the long stylocerite, the form of the telson, as well as the form and armature of the rostrum, Caridina qiongzhongensis sp. nov. is most similar to C. serrata Stimpson, 1860 , a species widely distributed along the coastal areas and islands of Guangdong. It can be easily separated from C. serrata by the slender endopod of the male first pleopod (endopod 2.77–3.09 times as long as wide vs. 2.5 times in C. serrata ); the shape and the spines of appendix masculina of the second pleopod (appendix masculina rod-shaped with slightly swollen tip, the long spiniform setae on the tip and the slightly shorter spiniform setae along the proximal inner margin vs. rod-shaped with slightly swollen midportion, equally stout spiniform setae along the inner margin and tip in C. serrata ); slightly bigger eggs (0.70–0.76 × 1.17–1.30 mm vs. 0.56–0.62 × 0.90–0.96 mm in C. serrata ).

Caridina qiongzhongensis sp. nov. is most similar to C. clinata Cai et al., 1999 , in shape of sexual appendages and the proportions between the joints of pereiopods. However, it can be separated from C. clinata by the fewer rostral teeth (dorsally with 8–12 teeth and ventrally with 0–2 teeth vs. dorsally with 12–21 teeth and ventrally with 1–5 teeth in C. clinata ); the longer stylocerite (beyond of basal antennular segment vs. not reaching basal antennular segment in C. clinata ); the slender scaphocerite (3.7 times as long as wide vs. 3.1–3.4 times in C. clinata ); more spinules on the uropodal diaresis (20–23 spinules vs. 14–21 spinules in C. clinata ); and slightly bigger eggs (0.70–0.76 × 1.17–1.30 mm vs. 0.60–0.75 × 1.10–1.15 mm in C. clinata ).

Caridina qiongzhongensis sp. nov. is morphologically similar to C. huangi sp. nov. in the form and armature of the rostrum, the long stylocerite, and the proportions between the joints of pereiopods. However, it can be separated by the slender endopod of the male first pleopod (2.77–3.09 times as long as wide vs. 2.40–2.82 times in C. huangi sp. nov.); the shape and the spines of appendix masculina of the second pleopod (appendix masculina rod-shaped with slightly swollen tip, the long spiniform setae on the tip and the slightly shorter spiniform setae along the proximal inner margin vs. cylindrical with uniform width, two rows of equally stout spiniform setae along the inner margin and tip in C. huangi sp. nov.); the posterior of the telson lacks a projection (vs. a projection present in C. huangi sp. nov.); and slightly bigger eggs (0.70–0.76 × 1.17–1.30 mm vs. 0.66–0.85 × 1.10–1.27 mm in C. huangi sp. nov.).

Molecular results.

The intraspecific p-distances of COI of the new species were 0 % – 0.6 %. The new species is most similar in genetic divergence (p-distance) to C. huangi sp. nov. (6.8 % – 8.0 %) and C. brevilineata sp. nov. (7.3 % – 7.5 %). According to molecular analysis, the distance between the new species and C. clinata is 13.5 % – 14.5 %. The intraspecific p-distances of 16 S rRNA of the new species were 0 % – 0.7 %. The new species is most similar in genetic divergence (p-distance) to C. hepingensis sp. nov. (1.6 % – 1.8 %) and C. huangi sp. nov. (2.2 % – 2.5 %). According to molecular analysis, the distance between the new species and C. clinata is 3.9 % – 5.0 % (Fig. 21 , Suppl. materials 1, 2).

Etymology.

The new species is named after its type locality name: Qiongzhong County.

Coloration.

Body translucent. Middle part of the plastron with a row of fine dark brown spots. Plastron margin with 4 slender vertical dark brown stripes; stripes in some individuals appear red. Middle part of the 6 th abdominal segment with 1 blue patch. (Fig. 2 D ).

Ecological notes.

C. qiongzhongensis sp. nov. was collected from site 6–7. At site 6, the stream measured 0.5 m in width and 0.2 m in depth, and its substrate consisted of rock, sand, and leaf litter. At site 7, the stream measured 2.0 m in width and 0.4 m in depth, and its substrate consisted of big rocks, gravel, and mud. The shrimps lived densely among leaf litter, exhibiting high population density. The stream water was intermediately flowing (Fig. 2 D , Table 1 ).

Distribution.

Only occurring in Yinggen Town, Qiongzhong County, Hainan Island.

Figures

Figure 2. Habitats of 9 Caridina species on Hainan Island. A. C. clinata Cai et al., 1999; B. C. caii sp. nov.; C. C. wenchangensis sp. nov.; D. C. qiongzhongensis sp. nov.; E. C. huangi sp. nov.; F. C. hepingensis sp. nov.; G. C. fontinalis sp. nov.; H. C. tunchengensis sp. nov.; I. C. brevilineata sp. nov.

Figure 9. Caridina qiongzhongensis Hou, Zhang & Guo, sp. nov. A. Holotype male (FU 5727015); B – H. Paratype male (FU 5727021): A, B. Cephalothorax; C. Antennular; D. Antenna; E. Mandible; F. Maxillula; G. Maxilla; H. First maxilliped.

Figure 10. Caridina qiongzhongensis Hou, Zhang & Guo, sp. nov. A – J. Paratype male (FU 5727021): A. Second maxilliped; B. Third maxilliped; C. First pereiopod; D. Second pereiopod; E. Third pereiopod; F. Fifth pereiopod; G. First pleopod of the male; H. Second pleopod of the male; I. Telson; J. Uropodal diaeresis.

Figure 21. Maximum likelihood method (ML) tree of 8 new species of Caridina and other atyids and 1 Macrobrachium species, based on the analysis of two mitochondrial gene fragments. Numbers on branches show ML bootstrap values (> 70). The scale bar indicates the substitution rate. The code following the species name is the specimen code.