Caridina clinata Cai, Nguyen & Ng, 1999

Figs 2 A, 3, 4

Caridina clinata Cai, Nguyen & Ng, 1999: 531–535, Figs 1, 2 [type locality: Cuc Phuong National Park, Ninh Binh Province, northern Vietnam].

Non Caridina clinata Cai, 2014: 207–231, Figs 10, 11.

Materials examined.

China – Hainan Island • 1 ♂, cl 3.3 mm, (FU 5725001); 1 ♂, cl 4.1 mm, (FU 5725002); 1 ♂, cl 3.4 mm, (FU 5725003); 1 ♂, cl 3.7 mm, (FU 5725004); 2 ♂, cl 3.5–4.1 mm, (FU 5725005); 1 ♀, cl 5.1 mm, (FU 5725006); 1 ♀, cl 4.9 mm, (FU 5725007); 1 ovigerous ♀, cl 5.3 mm, (FU 5725008), Baoyou Town, Ledong City, 18°49'48"N, 109°7'58"E, al. 306 m, stn. 1, coll. YU W. D., MA X. C. and HOU J. J., 27 Mar 2024 ; 1 ♀, cl 3.8 mm, (FU 5725009); 2 ♂♂, cl 3.9–4.1 mm, (FU 5725010), Jianfeng Town, Ledong City, 18°44'50"N, 109°2'27"E, al. 331 m, stn. 2, coll. YU W. D. and HOU J. J., 28 Feb. 2025 ; 2 ♂♂, cl 4.0– 4.2 mm, (FU 5725011), Jianfeng Town, Ledong City, 18°45'6"N, 109°2'11"E, al. 400 m, stn. 3, coll. YU W. D. and HOU J. J., 28 Feb. 2025 . Vietnam – Ninh Bình Prov. • 1 ♂, cl 3.5 mm, (FU 70000001); 1 ♂, cl 3.6 mm, (FU 70000002); 1 ♂, cl 3.9 mm, (FU 70000003); 1 ♂, cl 4.4 mm, (FU 70000004); 3 ♀♀, cl 3.9–4.9 mm, (FU 70000005), Cuc Phuong National Park, 20°19'11"N, 105°37'42"E, al. 293 m, stn. 13, 5 Mar. 2025 .

Description.

Body (Fig. 2 A): Small, slender and sub-cylindrical, males up to 4.4 mm cl, females up to 5.3 mm cl. Sixth abdominal somite 0.40–0.53 times as long as carapace.

Rostrum (Fig. 3 A): Short, slightly sloping downwards, reaching to the beginning to the end of the second segment of antennular peduncle; 0.4–0.5 of cl; armed dorsally with 12–16 teeth, including 4–6 on carapace posterior to orbital margin, ventrally with 1–5 teeth; lateral carina dividing rostrum into two unequal parts, continuing posteriorly to orbital margin.

Eyes (Fig. 3 A): Well developed, on short ocular peduncle, cornea globular.

Carapace (Fig. 3 A): Smooth, glabrous; antennal spine acute, fused with inferior orbital angle; pterygostomian margin broadly rectangular, slightly produced forward; pterygostomian spine absent.

Antennule (Fig. 3 B): Stylocerite reaching 0.67–0.93 times as long as basal segment of antennular peduncle; basal segment shorter than combined length of second and third segments, 1.54–1.70 times as long as second segment; second segment 1.12–1.49 times as long as third segments; all segments with marginal plumose setae.

Antenna (Fig. 3 C): Scaphocerite 3.1–3.2 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. 3 G): Palp of first maxilliped broadly triangular, ending in finger-like projection.

Third maxilliped (Fig. 4 B): Basal segment 0.89–1.09 times as long as penultimate segment; penultimate segment as long as distal segment, ending in a large claw-like spine surrounded by simple setae, preceded by 6–9 thin spines on distal third of posterior margin, proximally a clump of long and short simple, serrate setae; exopod reaching beyond the middle of second segament, distal margin with long plumose setae.

First pereiopod (Fig. 4 C): Chela 2.11–2.38 times as long as high, 1.26–1.42 times as long as carpus; movable finger 3.14–3.92 times as long as wide and 1.02–1.30 times as long as palm, setal brushes well developed; carpus 1.71–2.03 times as long as wide, slightly excavated distally; merus 0.99–1.21 times as long as carpus.

Second pereiopod (Fig. 4 D): Chela 2.83–3.29 times as long as high, 0.66–0.79 times as long as carpus; movable finger 3.97–4.81 times as long as wide and 1.46–1.58 times as long as palm, setal brushes well developed; carpus 5.42–6.30 times as long as wide, slightly excavated distally; merus 0.81–0.93 times as long as carpus.

Third pereiopod (Fig. 4 E): Dactylus 3.00–4.20 times as long as wide, terminating in a prominent claw-like spine surrounded by simple setae, followed by 5–6 spiniform setae; propodus 2.78–4.62 times as long as dactylus, 9.11–10.05 times as long as wide; carpus 0.64–0.70 times as long as propodus; merus 1.41–2.05 times as long as carpus, with 3 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. 4 F): Dactylus 4.53–5.71 times as long as wide, ending in prominent claw-like spine surrounded by simple setae, followed by a row of 41–51 spiniform setae; propodus 2.94–3.43 times as long as dactylus, 11.53–13.43 times as long as wide; carpus 0.49–0.69 times as long as propodus; merus 1.49–1.73 times as long as carpus, with 2–3 spiniform setae on the posterior margin.

First four pereiopods with epipod.

First pleopod (Fig. 4 G): Endopod in male 0.46–0.67 times as long as exopod, oblong-reniform, 2.40–3.04 times as long as distally wide, tip rounded; appendix interna well developed, arising from distal 0.33 of endopod, reaching slightly beyond the end of endopod, distally with cincinuli.

Second pleopod (Fig. 4 H): Appendix masculina club-shaped, reaching 0.60–0.70 length of exopod, some short spiniform setae on basal part, and inner margin and tip bearing nearly equal long and stout spiniform setae; appendix interna well developed, reaching 0.52–0.63 length of appendix masculina, distally with cincinuli.

Telson (Fig. 4 I): With 4–5 pairs of short spiniform setae dorsally and one pair of short spiniform setae dorsolaterally; posterior margin with 4 pairs of intermedial spiniform setae. Exopodite of the uropod (Fig. 4 J) bears a series of 18–21 movable spinules along diaresis.

Eggs: 0.65–0.70 mm × 1.07–1.20 mm in diameter.

Remarks.

Based on morphological descriptions and measurements above, our specimens from Ledong closely match the original description of Caridina clinata Cai et al., 1999 . However, some differences between the present material and the type specimens are evident, such as: the more slender carpus of the first pereiopod (1.71–2.03 times as long as high vs. 1.2–1.5 in type specimens); the more slender chela (2.83–3.29 times as long as high vs. 2.5 in type specimens) and carpus (5.42–6.30 times as long as high vs. 4.7 in type specimens) of the second pereiopod; more spinules on uropodal diaresis (18–21 vs. 14–17 in type specimens). Furthermore, our specimens exhibit a posteromedian telson projection (Fig. 4 I), contrasting with the description and illustration by Cai et al., who reported its absence (Cai et al. 1999: Fig. 2 A). However, this projection is consistently present in all examined topotypic specimens. Additionally, the scaphocerite length-to-width ratio in our material ranges from 3.10–3.20, aligning with topotypic specimens but differing from the type specimens (3.4). But the C. clinata specimens from Hainan Island and those from Vietnam are highly similar in the shape of the male first pleopod endopod and the male appendix masculina of the second pleopod, and show no significant genetic differentiation; thus, we still classify the Ledong population as Caridina clinata .

Molecular results.

Based on COI and 16 S rRNA sequence data (Fig. 21), the genetic divergence between Ledong and Vietnam populations is minimal, ranging from 0.6 % – 1.2 % for COI and 0.7 % – 1.6 % for 16 S rRNA. C. clinata from Hainan Island and from Vietnam are closely related in the ML phylogenetic tree based on COI and 16 S, and cluster well into a single clade (ML bootstrap values> 70). These low divergence values support the identification of the Ledong populations as C. clinata (Fig. 21, Suppl. materials 1, 2).

Coloration.

Body yellowish to gray and dark gray. There is one transverse black stripe which is irregularly broken at the lateral posterior margin of the carapace, some irregular black spots are present on the ventro-lateral parts of the carapace. The ventro-lateral portion of the abdominal tergal pleura is mottled with black spots adjacent to the articular knobs at the posterior bases of the pleura, black transverse stripes are present at the posteroventral ends of the first four pleura, the dorsum of the third abdominal somite has a black transverse stripe. The antenna, antennule and telson are yellowish to orange, the pereiopods are translucent to yellowish (Fig. 2 A).

Ecological notes.

C. clinata was collected from site 1–3. At site 1, the stream measured 0.5–1.0 m in width and 0.5 m in depth, and its substrate consisted of rock, mud and aquatic plants. At site 2, the stream measured 0.2–0.3 m in width and 0.1 m in depth, and its substrate consisted of rock, gravel and mud. At site 3, the stream measured 0.3 m in width and 0.1 m in depth, and its substrate consisted of rock, mud and leaf litter. The shrimps live densely among leaf litter and marginal vegetation. The stream water was intermediately flowing (Fig. 2 A, Table 1).

Distribution.

Hainan Island, China and Vietnam.