Caridina xuanlien, Do & Phan & von Rintelen & Le & von Rintelen, 2025

Do, Van Tu, Phan, Thi Yen, von Rintelen, Kristina, Le, Hung Anh & von Rintelen, Thomas, 2025, Descriptions of four new species of atyid shrimp (Crustacea, Decapoda, Atyidae) in Vietnam, ZooKeys 1247, pp. 151-186 : 151-186

Caridina xuanlien sp. nov.

Figs 6 , 7 , 8

Type material.

Holotype. • Adult male, cl 4.5 mm, IB -FS 008 , Vietnam, Thanh Hoa Province, Thuong Xuan District, Yen Nhan Commune, a small stream in Xuan Lien National Park , 19°56'05.9"N, 105°07'30.6"E, 21 November 2021, collected by Van Tu Do . Paratypes. • 8 females, cl 4.0– 4.8 mm, 11 males, cl 3.6–4.7 mm, 49 additional specimens, ZMB 32948 , same data as holotype ; male, cl 4.5 mm, female, cl. 4.6 mm, 107 additional specimens, ZMB 32944 , Vietnam, Thanh Hoa Province, Thuong Xuan District, Van Xuan Commune, a small stream in Xuan Lien National Park , 19°55'15.0"N, 105°09'12.3"E, 24 October 2021, collected by Van Tu Do .

Comparative material.

Caridina nguyeni Li & Liang, 2002 : • adult male, cl. 4.7 mm, ZMB 30280 , Vietnam, Cao Bang Province, Ha Quang District, Truong Ha Commune, Pac Bo village , a small stream near Le Nin stream, 22°59'4"N, 106°2'53.7"E, 25 May 2017, collected by Van Tu Do.

Diagnosis.

Caridina xuanlien sp. nov. is characterized by several morphological characters such as short rostrum, just reaching to beginning of the third segment of antennular peduncle; stylocerite reaching to beginning of second segment of antennular peduncle (Fig. 6 A, B ); dactylus of first pereiopod longer than palm (Fig. 7 A ); short, kidney-shaped endopod of male first pleopod, extending to 2.79 × exopod, with well-developed appendix interna, slightly exceeding terminal margin of endopod by 0.23 its length (Fig. 7 G, H ); short and stick-shaped appendix masculina of male second pleopod, reaching to proximal 0.43 × endopod length, with narrow and small appendix interna, extending ~ 0.6 × length of appendix masculina (Fig. 7 I, J ).

Description.

Cephalothorax and cephalic appendages. Carapace length 3.6–4.8 mm (median 4.3 mm, n = 20). Rostrum short and slender, slightly downward, reaching to beginning of the third segment of antennular peduncle, 0.1–0.2 (median 0.2) × as long as carapace, rostral formula 2–7 + 3 – 9 / 0 – 2 (Fig. 6 A ). Suborbital angle acute, completely fused with antennal spine; pterygostomian margin rounded, slightly produced forward (Fig. 6 A ). Eyes well developed with globular cornea, anterior end reaching to 0.7 × length of basal segment of antennular peduncle (Fig. 6 A ). Antennular peduncle 0.6–0.74 (median 0.64) × as long as carapace; basal segment 1.63–2.0 (median 1.88) × as long as second segment, second segment 1.17–1.4 (median 1.33) × as long as third segment (Fig. 6 B ). Stylocerite reaching to beginning of second segment of antennular peduncle (Fig. 6 B ). Scaphocerite elongated ovate, reaching beyond distal end of antennular peduncle, 2.68–2.88 (median 2.86) × as long as wide (Fig. 6 A, C ).

Abdominal somites, telson, and uropods. Sixth abdominal somite 0.47–0.5 (median 0.47) × length of carapace, 1.47–1.62 (median 1.58) × as long as fifth abdominal somite, 0.85–0.95 (median 0.91) × length of telson. Telson 2.4–3.25 (median 2.75) × as long as proximal wide, distal margin triangular, terminating in a short median projection, with five or six pairs of dorsal spiniform setae and one pair of dorso-subdistal spiniform setae; distal end with three or four pairs of spiniform setae, lateral pair shorter than intermediate pairs (Fig. 6 D, E ). Preanal carina low ,, with few setae, lacking a spine (Fig. 6 F ). Uropodal diaeresis with 18–21 (median 21) movable spiniform setae, outermost shorter than lateral angle (Fig. 6 G ).

Mouthparts and branchiae. Incisor process of mandible ending in one row of six or seven irregular teeth, molar process truncated (Fig. 6 H ). Lower lacinia of maxillula broadly rounded, upper lacinia elongated, with a several distinct teeth and setae on inner margin, palp stout with few simple setae at tip (Fig. 6 I ). Upper endites of maxilla subdivided, palp short, scaphognathite tapering posteriorly, with numerous long, curved setae at posterior margin (Fig. 6 J ). Distal end of palp of first maxilliped triangular, with a short projection; flagellum of the exopod very elongated, endopod reaching 0.8 × length of flagellum of exopod (Fig. 6 K, L ). Podobranch of second maxilliped slightly reduced, with few finger-like projections (Fig. 6 M ). Third maxilliped reaching near the end of antennular peduncle, ending in single terminal claw, exopod reaching 0.3 × length of penultimate segment; ultimate segment slightly longer penultimate segment; epipod present on the coxa (Fig. 6 N ). Branchial formula as typical for Paracaridina genus, five pairs of pleurobranchs well developed; two pairs of arthrobranchs on third maxillipeds, with second pair strongly reduced in size; one pair of podobranchs on second maxillipeds slightly reduced, arthrobranch on first pereiopod absent ( Liang et al. 1999).

Pereiopods. Epipods present on first to fourth pereiopods. First pereiopod short, robust, reaching end of basal segment of antennular peduncle; chela 2.08–2.29 (median 2.12) × as long as wide, 1.21–1.47 (median 1.40) × length of carpus; tips of fingers rounded, without hook; dactylus longer than palm, 1.0–1.07 (median 1.03) × as long as palm; carpus excavated strongly anteriorly, 1.5–1.87 (median 1.73) × as long as, respectively; carpus 0.78–0.91 (median 0.84) × length of merus; merus 2.65–3.54 (median 3.33) × as long as wide, longer than ischium (Fig. 7 A ). Second pereiopod long, slender, reaching to distal end of antennular peduncle; chela 2.65–3.0 (median 2.86) × as long as wide, 0.66–0.74 (median 0.73) × length of carpus; tips of fingers rounded, without hook; dactylus 1.42–1.58 (median 1.46) × as long as palm; carpus 5.25–6.21 (median 5.6) × as long as wide, 1.05–1.21 (median 1.16) × as long as merus; merus 5.46–6.0 (median 5.71) × as long as wide, longer than ischium (Fig. 7 B ). Third pereiopod slender, reaching beyond distal end of antennular peduncle by its dactylus, terminating in one claw, with five accessory spiniform setae on flexor margin, dactylus 3.29–4 (median 3.57) × as long as wide (terminal claw and spiniform setae on flexor margin included), propodus 8.9–9.44 (median 9.0) × as long as wide, 3.24–4.0 (median 3.71) × as long as dactylus; carpus 4.2–4.92 (median 4.83) × as long as wide, 0.69–0.78 (median 0.72) × as long as propodus, 0.5–0.57 (median 0.56) × as long as merus; merus 5.75–6.82 (median 6.0) × as long as wide, bearing three strong, movable spiniform setae on posterior margin of outer surface; ischium with one small movable spiniform seta (Fig. 7 C, D ). Fifth pereiopod slender, reaching to end of third segment of antennular peduncle, dactylus 3.33–3.75 (median 3.5) × as long as wide (terminal claw and spiniform setae on flexor margin included), terminating in one large claw, with 37–40 spiniform setae on flexor margin; propodus 10.88–13.13 (median 11.88) × as long as wide, 3.22–3.53 (median 3.33) × length of dactylus; carpus 4.15–4.36 (median 4.28) × as long as wide, 0.52–0.55 (median 0.55) × as long as propodus, 0.6–0.69 (median 0.62) × as long as merus; merus 5.83–7.17 (median 6.57) × as long as wide, bearing 3 strong, movable spiniform setae on posterior margin of outer surface, ischium without movable spiniform setae (Fig. 7 E, F ).

Pleopods. Endopod of male first pleopod extending to 0.59 × exopod, kidney-shaped, anterior part not folded backwards, 2.75–3.05 (median 2.79) × as long as proximal width, inner margin concave, outer margin slightly convex, rounded distally, long pappose setae on outer and distal margins, medium-length setae on inner margin; with appendix interna curved upwards, slightly exceeding terminal margin of endopod by 0.23 of its length (Fig. 7 G, H ). Appendix masculina of male second pleopod slender, reaching to proximal 0.6 × endopod length, 8.25 × as long as distal width, stick-shaped, with some short spiniform setae on outer surface and some long spiniform setae on distal surface; appendix interna at the middle of appendix masculina, narrow, small, extending ~ 0.60 length of appendix masculina (Fig. 7 I, J ).

Coloration.

The body is white to slightly yellowish in color, with many small black spots and small lines of irregular sizes (Fig. 8 ).

Etymology.

The new species is named after the type locality, Xuan Lien National Park. The name is used as a noun in apposition.

Habitat.

This new species was found in the streams running in the forests. The substratum includes bedrock, stone, boulder, gravel, and sand in a water depth of 0.3–0.8 m (Fig. 9 ).

Distribution.

This species has been found only in the upland streams of Thuong Xuan District, Thanh Hoa Province, with elevations from 130 m to 600 m. The estimated area of occupancy is less than 1000 km 2.

Molecular phylogenetic results.

Caridina xuanlien sp. nov. is well supported as the sister species to C. clinata (Fig. 18 ). The minimum genetic divergence (p-distance) to C. clinata ) is 4.0 % (COI) and 1.5 % (16 S), respectively (Suppl. materials 1, 2).

Remarks.

The new species is quite similar to C. nguyeni from Cao Bang province, northeast Vietnam, in the shape of the rostrum and endopod of male first pleopod ( Li and Liang 2002). However, it can be separated by the number of dorsal teeth on the rostrum anterior to the orbital margin (3–9 vs 9–12), the number of ventral teeth of the rostrum (0–2 vs 1–4); the length of stylocerite (reaching to the beginning of the second segment of antennular peduncle vs reaching to beyond the middle to the end of second segment of the antennular peduncle); the appendix interna of the second male pleopod (~ 0.6 of the length of the appendix masculina vs ~ 0.4 length of appendix masculina); the uropodal diaeresis (with 18–21 movable spiniform setae vs with 12–18 movable spiniform setae) (Figs 6 A, B , 7 G, H ; cf. Li and Liang 2002, figs 1 A, C, 2 C, B).

The new species resembles Caridina clinata Cai, Quynh & Ng, 1999 in the shape of the endopod of male first pleopod, appendix masculine, and appendix interna of male second pleopod. However, C. xuanlien sp. nov. can be separated from C. clinata by a longer rostrum, reaching to the beginning of third segment of antennular peduncle (vs not reaching distal margin of basal segment of antennular peduncle); fewer number of teeth on the rostrum, armed with 3–9 dorsal teeth on anterior to the orbital margin and 0–2 ventral teeth (vs 10–16 dorsal teeth on anterior to the orbital margin and 2–5 ventral teeth); a longer stylocertite, reaching beginning of second segment of antennular peduncle (vs not reaching to distal margin of basal segment of antennular peduncle); slender endopod of male first pleopod, 2.75 × as long as proximal width (vs 2.5 × as long as proximal width); higher number of movable spiniform setae on uropodal diaresis, 18–21 (vs 14–17 movable spiniform setae); higher number of spiniform setae on flexor margin of the dactylus of fifth pereiopod, 37–40 (vs 45–49 spiniform setae on flexor margin) (Figs 6 A, B, G , 7 H, F ; cf. Cai et al. 1999: figs 1 A, B, D, K, 2 F).

Figures

Figure 6. Caridina xuanlien sp. nov. adult male, cl 4.5 mm (ZMB 32948). A. Cephalothorax and cephalic appendages, lateral view; B. Antennular peduncle; C. Scaphocerite; D. Telson; E. Distal portion of telson; F. Preanal carina; G. Uropodal diaeresis; H. Mandible; I. Maxillula; J. Maxilla; K. First maxilliped; L. Distal end of palp of first maxilliped; M. Second maxilliped; N. Third maxilliped. Scale bars: 1 mm (A); 0.5 mm (B – D); 0.2 mm (E – K, M, N); 0.1 mm (L).

Figure 7. Caridina xuanlien sp. nov. adult male, cl 4.5 mm (ZMB 32948). A. First pereiopod; B. Second pereiopod; C. Third pereiopod; D. The same, dactylus; E. Fifth pereiopod; F. The same, dactylus; G. Male first pleopod; H. Endopod of male first pleopod; I. Male second pleopod; J. Appendix masculina and interna of male second pleopod. Scale bars: 1 mm (A, B, C, F, G, I); 0.2 mm (D, E, H, J).

Figure 8. Live coloration of four specimens of Caridina xuanlien sp. nov. (ZMB 32948), collected in Thanh Hoa Province, Vietnam.

Figure 9. Habitat of Caridina xuanlien sp. nov. (ZMB 32948) in Thanh Hoa Province, Vietnam.

Figure 18. Bayesian Inference phylogram showing the relationships of the four new species of Caridina to other Vietnamese atyids, based on the analysis of two mitochondrial gene fragments. Numbers on branches show Bayesian posterior probabilities (> 0.7) and ML bootstrap values (> 70). An asterisk (*) indicates nodes with full support (1 / 100) in both analyses. The scale bar indicates the substitution rate. Numbers in brackets give the DNA accession number at MfN (MfN DNA Crust). See Table 1 for information on the sequenced specimens.