Description of a new species of freshwater shrimp (Decapoda: Caridea: Atyidae) from Mount Danxia, Guangdong, China, based on morphological and molecular evidence Author Wang, Yaqin 0000-0002-5294-0163 Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-Sen University, Shenzhen, China. Author Chu, Ka Hou Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China. & School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China. Author Ma, Ka Yan Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-Sen University, Shenzhen, China. text Zootaxa 2024 2024-07-04 5476 1 447 462 http://dx.doi.org/10.11646/zootaxa.5476.1.33 journal article 299627 10.11646/zootaxa.5476.1.33 4e961ee5-4686-4979-be35-32b0225b3760 1175-5326 12696573 DBC661F8-7400-4B8F-8FD3-E04F65C08000 Caridina danxiaensis sp. nov. ( Figs. 1–3 ) FIGURE 1 . Caridina danxiaensis sp. nov. : A, C–E from holotype male, (SYS_Csp_GDDXWLG3_13); B, F–J from paratype female (SYS_Csp_GDDXWLG3_7). A, cephalothorax and cephalic appendages, lateral view; B, left antennule, lateral view; C, right antenna with scaphocerite, lateral view; D, telson, dorsal view; E, right uropodal diaeresis, lateral view; F, mandible, lateral view; G, maxillula, lateral view; H, maxilla, lateral view; I, first maxilliped, lateral view; J, second maxilliped, lateral view. Type material. Holotype : male (cl 4.2 mm , tbl 14.5 mm ) (SYS_Csp_GDDXWLG3_13), collected by hand nets, Wolong Hill , Danxia Mountain National Nature Reserve of Shaoguan City , Renhua County , Shaoguan City , Guangdong province , China , 113°45’21.02”E , 25°0’12.48”N , 02 April 2022 . Paratypes : 3 females (cl 4.3mm , tbl 14.5 mm ; cl 4.8 mm , tbl 15.4 mm ; cl 4.2mm , tbl 14.2 mm ) (SYS_Csp_GDDXWLG3_7, SYS_Csp_GDDXWLG3_ 8, SYS_Csp_GDDXWLG3_14), same collection data as holotype . Description . Carapace ( Fig. 1A ) length 4.2–4.8 mm . Rostrum short, straight, rather slender, dorsal margin nearly horizontal, reaching to midlength of second segment of antennular peduncle, 0.55–0.58 times as long as carapace; rostral formula 5–8+7–8/0 evenly spaced teeth. Suborbital angle indistinct, partially fused with antennal spine, pterygostomian margin rounded. Eyes well developed, anterior end reaching to 0.61–0.64 times length of basal segment of antennular peduncle. Antennular peduncle 0.50–0.51 times as long as carapace, basal segment of antennular peduncle longer than sum of second and third segment length, anterolateral angle pointed, reaching 0.25 times length of the second segment, second segment distinctly longer than third segment ( Fig. 1B ). Stylocerite reaching distal end of basal segment of antennular peduncle. Scaphocerite ovate, 3.8–3.9 times as long as wide, lateral tooth not nearly reaching distal margin of scaphocerite ( Fig. 1C ). Sixth abdominal somite 0.46–0.48 times length of carapace, 1.33–1.47 times as long as fifth somite, slightly shorter than telson. Telson 4.5–4.8 times as long as proximal wide, distal margin triangular, terminating in a short median projection, with 4 pairs of dorsal spiniform spines and one pair of dorso-subdistal spiniform setae; posterior margin with 4 pairs of nearly equal long intermedial plumose setae ( Fig. 1D ). Preanal carina unarmed. Uropodal diaeresis with 19–23 movable spiniform setae ( Fig. 1E ). Mandible ( Fig. 1F ) without palp; left incisor process with 6 sharp teeth; medially with two groups of setae; molar process ridged. Maxillula ( Fig. 1G ) with simple and stout palp, bearing few simple setae at tip; lower lacinia broadly rounded, upper lacinia broadly elongated, inner edge straight, with distinct teeth and setae. Maxilla ( Fig. 1H ) with scaphognathite tapers posteriorly, with numerous long plumose setae at posterior margin distally and short marginal setae continuing down proximal triangular process; upper and middle endites with marginal simple, and sub-marginal simple setae. First maxilliped ( Fig. 1I ) with palp broadly triangular ending in finger-like tip and with terminal long plumose setae; caridean lobe broad; exopodal flagellum well developed; distal end of endopod with numerous long setae. Second maxilliped ( Fig. 1J ) with inner margin of ultimate and basal segments with dense long setae, penultimate segments with 11 long plumose setae; exopod long with long plumose setae; podobranch well developed, with finger-like projections. Third maxilliped ( Fig. 2A ) nearly reaches to distal end of second antennular peduncle segment, endopod threesegmented, ending in single terminal claw, ultimate segment slightly shorter than penultimate segment; exopod reaching 0.36 times length of penultimate segment; serrate setae; exopod reaches to 0.45–0.50 times of second segment of endopod, distal margin with long plumose setae. Branchial formula typical for genus. First pereiopod ( Fig. 2B ) chela 2.0–2.2 times as long as wide, 1.50–1.70 times as long as carpus; dactylus 0.89–1.02 times as long as palm; carpus strongly excavated distally, 1.27–1.46 times as long as wide, 0.63–0.77 times as long as merus. Second pereiopod ( Fig. 2C ) chela 2.72–2.78 times as long as wide, 0.78–0.88 times as long as carpus; dactylus 1.6–2.0 times as long as palm; carpus 4.2–4.4 times as long as wide, 1.10–1.14 times as long as merus. Third pereiopod ( Fig. 2D ) not sexually dimorphic, dactylus with 5 accessory spiniform setae on flexor margin, 2.9–3.2 times as long as wide (terminal claw and accessory spiniform setae included); propodus 8–9 times as long as wide, 3.9–4.1 times as long as dactylus, bearing 12–14 strong, movable spiniform setae on posterior margin of outer surface; carpus bearing two movable spiniform setae on posterior margin of outer surface; ischium without movable spiniform seta. Fourth pereiopod extending to distal end of second segment of antennular peduncle; its structure and form similar to third pereiopod. Fifth pereiopod ( Fig. 2E, F ) dactylus with 26–32 accessory spiniform setae on flexor margin, terminating in one large claw, 1.85–2.09 times as long as wide (terminal claw and accessory spiniform setae included); propodus 8.2–9.5 times as long as wide, 4.6–5.0 times as long as dactylus, bearing 8–10 strong, movable spiniform setae on posterior margin of outer surface; carpus bearing one movable spiniform setae on posterior margin of outer surface; ischium without movable spiniform seta. Epipods present on first four pereiopods. Endopod ( Fig. 2G ) of male first pleopod subrectangular, anterior part not folded backward, 3.79 times as long as wide, about 0.74 times as long as exopod, inner margin concave, outer margin slightly convex, rounded distally, long plumose setae on outer and distal margins, strong and short setae on inner margin; with appendix interna exceeding terminal margin of endopod by 0.37 its length. FIGURE 2 . Caridina danxiaensis sp. nov. : A–C from holotype male, (SYS_Csp_GDDXWLG3_13); D–I from paratype female (SYS_Csp_GDDXWLG3_8). A, right third maxilliped, lateral view; B, right first pereiopod, lateral view; C, right second pereiopod, lateral view; D, right third pereiopod, lateral view; E, right fifth pereiopod, lateral view; F, dactylus of fifth pereiopod, lateral view. G, endopod of first right pleopod, lateral view; H, I, appendix masculina of second right pleopod, lateral view. Appendix masculina of second pleopod ( Fig. 2H, I ) rod-shaped, 7.51 times as long as distal width, reaching to about 0.65 times length of endopod, with some short spiniform setae on basal part and some long spiniform setae on outer and distal surface; appendix interna at the middle of appendix masculina, extending about 0.8 times length of appendix masculine, distally with many cincinulli. FIGURE 3 . A, collection site of Caridina danxiaensis sp. nov. in Shaoguan Danxia Mountain National Nature Reserve; B, photos of live specimens of Caridina danxiaensis sp. nov. TABLE 1 . Pairwise genetic distances among 24 species of Caridina ( Atyidae ) based on the 16S rRNA gene sequences. DNA accession number are listed in the species column.

Species	Accession number	1	2	3	4	5	6	7	8	9	10	11	12	13	14
1. Caridina danxiaensis	PP192036	/
2. Caridina clinata	MT526810	0.057
3. Caridina rubropunctata	MT526819	0.074	0.06
4. Caridina cavernicola	MZ753802	0.074	0.06	0.065
5. Caridina tricincta	MT526822	0.077	0.062	0.069	0.053
6. Caridina serrata	KP168756	0.079	0.058	0.053	0.062	0.074
7. Caridina thachlam	MW505994	0.082	0.055	0.057	0.065	0.053	0.074
8. Caridina trifasciata	KP168767	0.082	0.053	0.045	0.062	0.072	0.029	0.064
9. Caridina haivanensis	MT526813	0.082	0.029	0.065	0.075	0.074	0.067	0.055	0.062
10. Caridina mariae	KP168753	0.084	0.082	0.069	0.077	0.072	0.072	0.067	0.072	0.077
11. Caridina pseudoserrata	MT526818	0.084	0.06	0.062	0.048	0.055	0.062	0.06	0.06	0.06	0.062
12. Caridina nanaoensis	KP168754	0.084	0.063	0.057	0.067	0.079	0.004	0.079	0.034	0.07	0.072	0.067
13. Caridina logemanni	KP168745	0.085	0.082	0.077	0.072	0.079	0.069	0.072	0.077	0.084	0.034	0.067	0.069
14. Caridina cucphuongensis	MT526811	0.087	0.048	0.067	0.075	0.079	0.077	0.067	0.062	0.06	0.105	0.085	0.077	0.1
15. Caridina nguyeni	MT526816	0.089	0.082	0.086	0.092	0.084	0.104	0.092	0.089	0.089	0.094	0.072	0.109	0.092	0.107
16. Caridina breviata	KP168718	0.089	0.085	0.065	0.053	0.07	0.07	0.07	0.065	0.082	0.072	0.058	0.074	0.07	0.098
17. Caridina pacbo	MW525213	0.089	0.075	0.057	0.072	0.069	0.084	0.074	0.07	0.084	0.092	0.058	0.089	0.077	0.077
18. Caridina cantonensis	KP168720	0.09	0.084	0.072	0.075	0.082	0.069	0.074	0.067	0.084	0.032	0.067	0.069	0.02	0.095
19. Caridina impensa	KP168741	0.092	0.072	0.057	0.067	0.07	0.079	0.057	0.067	0.067	0.069	0.062	0.079	0.069	0.074
20. Caridina namdat	MZ484402	0.092	0.072	0.062	0.065	0.06	0.074	0.082	0.067	0.087	0.077	0.039	0.079	0.074	0.082
21. Caridina longshan	OP177695	0.097	0.084	0.069	0.09	0.067	0.097	0.053	0.087	0.079	0.069	0.08	0.097	0.074	0.089
22. Caridina formosae	DQ478496	0.099	0.092	0.081	0.084	0.097	0.099	0.086	0.082	0.094	0.102	0.092	0.104	0.099	0.082
23. Caridina maculata	KP168750	0.1	0.077	0.065	0.088	0.072	0.084	0.053	0.072	0.072	0.077	0.072	0.089	0.084	0.077
24. Caridina sinanensis	MT434873	0.1	0.079	0.082	0.075	0.072	0.097	0.053	0.077	0.069	0.07	0.07	0.097	0.072	0.085
25. Caridina venusta	KP168771	0.102	0.089	0.079	0.09	0.1	0.107	0.074	0.089	0.084	0.087	0.087	0.112	0.087	0.094
26. Caridina conghuensis	KP168735	0.102	0.079	0.079	0.09	0.087	0.084	0.079	0.074	0.082	0.079	0.079	0.089	0.079	0.095
27. Caridina huananensis	MT446453	0.107	0.092	0.084	0.09	0.1	0.112	0.079	0.095	0.089	0.092	0.089	0.118	0.092	0.1
28. Caridina caobangensis	MT526809	0.116	0.093	0.084	0.075	0.085	0.092	0.087	0.092	0.095	0.097	0.075	0.097	0.104	0.09
29. Caridina lanceifrons	MT446450	0.131	0.113	0.104	0.097	0.104	0.115	0.104	0.112	0.107	0.119	0.092	0.12	0.104	0.123

.....Continued on the next page TABLE 1. (Continued)

Species	A c c e s s i o n number	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29
15. Caridina nguyeni	MT526816
16. Caridina breviata	KP168718	0.099
17. Caridina pacbo	MW525213	0.089	0.084
18. Caridina cantonensis	KP168720	0.087	0.07	0.074
19. Caridina impensa	KP168741	0.091	0.079	0.084	0.074
20. Caridina namdat	MZ484402	0.087	0.074	0.048	0.074	0.079
21. Caridina longshan	OP177695	0.094	0.084	0.089	0.077	0.055	0.087
22. Caridina formosae	DQ478496	0.094	0.099	0.089	0.094	0.089	0.092	0.089
23. Caridina maculata	KP168750	0.104	0.09	0.082	0.087	0.058	0.077	0.06	0.089
24. Caridina sinanensis	MT434873	0.092	0.082	0.09	0.075	0.057	0.085	0.027	0.097	0.06
25. Caridina venusta	KP168771	0.104	0.095	0.087	0.084	0.074	0.092	0.077	0.094	0.038	0.067
26. Caridina conghuensis	KP168735	0.096	0.077	0.09	0.072	0.087	0.092	0.091	0.112	0.089	0.084	0.097
27. Caridina huananensis	MT446453	0.102	0.1	0.089	0.09	0.079	0.094	0.077	0.099	0.043	0.072	0.004	0.099
28. Caridina caobangensis	MT526809	0.112	0.079	0.097	0.107	0.089	0.082	0.097	0.099	0.1	0.105	0.123	0.097	0.126
29. Caridina lanceifrons	MT446450	0.107	0.104	0.102	0.102	0.101	0.104	0.104	0.117	0.12	0.112	0.125	0.104	0.122	0.112	/

TABLE 2 . Key morphological differences between Caridina danxiaensis and morphologically similar species.

Species	Locality	Rostrum length	Stylocerite	Rostrum formula	Spiniform	Reference
Caridina danxiaensis	Renhua County,	Reaching to midlength of	Mostly reaching beyond distal end of	5–8+7–8/0	19–23	this study
(this study)	Guangdong Province,	second segment of antennular	basal segment of antennular peduncle,
China	peduncle	not to the middle of second segment of
antennular peduncle
Caridina acuta *	Libo County,	Reaching to or slightly	Not reaching distal end of basal segment	0+0–2/0	17–18	Liang et al.
Guizhou Province,	exceeding distal margin of	of antennular peduncle	(2005)
China	basal antennular segment, not
reaching as far as middle of
second segment
Caridina baoting *	Hainan Province,	Reaching to or slightly	Mostly reaching distal end of basal	0+1–4/1	23	Cai (2014)
China	exceeding distal margin of	segment of antennular peduncle
basal antennular segment, not
reaching as far as middle of
second segment
Caridina breviata	Hailing Dao Island,	Reaching to or slightly	Reaching beyond distal end of basal	0–2+6/0	16–20	Liang (2004)
Guangdong Province,	exceeding distal margin of	segment of antennular peduncle, not
China	basal antennular segment	to the middle of second segment of
antennular peduncle
Caridina cantonensis	Qingyuan,	Reaching to second segment	Reaching beyond distal end of basal	5–7+2–12/2–6	12–21	Liang (2004)
Guangdong Province,	of antennular peduncle	segment of antennular peduncle, even
China	to the middle of second segment of
antennular peduncle
Caridina caobangensis	Northern Vietnam	Reaching to second	Mostly reaching beyond distal end of	5–7+7–11/3–4	21–22	Li & Liang
segment or third segment of	basal segment of antennular peduncle,	(2002)
antennular peduncle	not to the middle of second segment of
antennular peduncle
Caridina cavernicola	Du’an County,	Overreaching to third	Not reaching distal end of basal segment	7–10+18–29/20–24	12–15	Liang (2004)
Guangxi Province,	segment of antennular	of antennular peduncle
China	peduncle

......Continued on the next page TABLE 2 . (Continued)

Species	Locality	Rostrum length	Stylocerite	Rostrum formula	Spiniform	Reference
Caridina clinata	Northern Vietnam	Reaching to or slightly	Not reaching distal end of basal segment	2–5+10–10/2–5	14–17	Cai et al. (1999)
exceeding distal margin of	of antennular peduncle
basal antennular segment, not
reaching as far as middle of
second segment
Caridina conghuensis	New Territories,	Reaching to midlength or	Reaching beyond distal end of basal	3–5+7–9/2–4	17–21	Klotz & Von
Hong Kong, China	end of second segment of	segment of antennular peduncle, not	Rintelen (2014)
antennular peduncle	to the middle of second segment of
antennular peduncle
Caridina cucphuongensis	Northern Vietnam	Just overreaching the eyes	Reaching to end of second segment of	1–3+5–7/0–2	18–21	Yen, et al.
to reaching to the base of	antennular peduncle or at least 0.7 times	(2021)
second segment of antennular	of it
peduncle
Caridina formosae	Taiwan Province,	Not reaching to distal	Not reaching distal end of basal segment	0/0	19–22	Liang (2004)
China	margin of basal segment of	of antennular peduncle
antennular peduncle
Caridina haivanensis	Thua Thien-Hue, Hai	Reaching to or slightly	Not reaching to distal end of basal	0+4–11/1–3	13–16	Tan (1990)
Van, Vietnam	exceeding distal margin of	segment of antennular peduncle
basal antennular segment, not
reaching as far as middle of
second segment
Caridina huananensis	Guangdong Province,	Not reaching to distal	Nearly reaching to distal end of basal	0/1	21–24	Liang (2004)
China	margin of basal segment of	segment of antennular peduncle
antennular peduncle
Caridina jiangkou *	Jiangkou County,	Short, straight, reaching to	Reaching 0.75 basal segment length of	0–5+4–7/1–5.	13	Cai & Ng (2018)
Guizhou Province,	distal end of basal segment of	antennular peduncle
China	antennular peduncle
Caridina lanceifrons	Southern China	Overreaching to third	Not reaching to distal end of basal	4+10–19/2–5	15–19	Liang (2004)
segment of antennular	segment of antennular peduncle
peduncle

......Continued on the next page TABLE 2 . (Continued)

Species	Locality	Rostrum length	Stylocerite	Rostrum formula	Spiniform	Reference
Caridina logemanni	New Territories,	Reaching to end of basal	Reaching to 0.40–0.50 times of second	3–7 + 7–15 / 0–6	17–22	Klotz & Von
Hong Kong, China	segment of antennular	segment of antennular peduncle	Rintelen (2014)
peduncle, 0.30–0.48 (median
0.37) times as long as
carapace
Caridina longshan	Longshan County,	Long, reaching from end of	Not reaching to distal end of basal	6–7+12–15/12–17	11–12	Cai & Ng (2018)
Hunan Province,	antennular peduncle to end of	segment of antennular peduncle
China	scaphocerite
Caridina maculata	Yingde County,	Short, nearly reaching the end	Reaching beyond distal end of basal	1–3+6–11/2–3	22	Wang et al. 2008
Guangdong Province,	of 1st segment of antennal	segment of antennular peduncle
China	peduncle
Caridina macauensis *	Macau, China	Never reaching beyond distal	Reaching beyond distal end of basal	0+0–3/1–3	18–20	Zhou et al.
end of basal segment of	segment of antennular peduncle, even	(2021)
antennular peduncle in lateral	to the middle of second segment of
view	antennular peduncle
Caridina mariae	New Territories,	Reaching to midlength of	Mostly reaching to end of second	4–6 + 6–9/1–2	16–20	Klotz & Von
Hong Kong, China	second segment of antennular	segment of antennular peduncle or at	Rintelen (2014)
peduncle or less frequent to	least 0.7 times of it
begin or end of this segment
Caridina namdat	Bac Kan Province,	Reaching to middle of	Reaching to 0.8 times length of basal	0/0	15–18	Do et al. (2021a)
Northeast Vietnam	basal segment of antennular	segment of antennular peduncle
peduncle
Caridina nanaoensis	Guangdong Province,	Reaching as far as middle of	Reaching as far as middle of second	5–8+5–18/2–6	18–24	Liang (2004)
China	second segment	segment antennular peduncle
Caridina nguyeni	Cao Bang, Ha Quang,	Reaching to second	Reaching as far as middle of second	9–12+8–16/4–6	12–18	Li & Liang
Truong Ha, Pac Bo,	segment or third segment of	segment antennular peduncle	(2002)
Vietnam	antennular peduncle

......Continued on the next page TABLE 2 . (Continued)

Species	Locality	Rostrum length	Stylocerite	Rostrum formula	Spiniform	Reference
Caridina pacbo	Cao Bang, Ha Quang,	Short, reaching beyond	Mostly reaching beyond the end of basal	2–6+5–12/0–3	19–20	Do et al. (2020)
Truong Ha, Pac Bo,	middle or close to end of	segment, sometimes to the middle of
Vietnam	basal segment of antennular	second segment of antennular peduncle
peduncle
Caridina pingi *	Jiangsu Province,	Overreaching the distal	Not reaching distal end of basal segment	0+9–16/0–4	16–20	Liang (2004)
China	margin of second antennular	of antennular peduncle
segment
Caridina pseudoserrata	Cao Bang, Quang	Reaching the middle of the	/	5–6+5–13/1–2	19–21	Dang & Do
Yen, Tu Do, Vietnam	second antennular segment	(2007)
Caridina rubropunctata	Thai Nguyen, Dong	Overreaching the 2nd	Reaching as far as middle of second	5–7+5–11/2–4	16–19	Dang & Do
Hy, Van Lang,	segment to the middle of	segment antennular peduncle	(2007)
Vietnam	the 3nd segment of the
antennular peduncle
Caridina serrata	New territories, Hong	Reaching to base of second	Nearly reaching the middle of second	0–5+5–12/0–6	18–21	Cai & Ng (1999)
Kong, China	segment of antennular	segment antennular peduncle
peduncle or nearly to distal
end of this segment
Caridina sinanensis	Pengjiaao, Tangtou	Reaching to the end of the	Short, reaching 0.75–0.88 length of basal	4–10+10–16/3–11	10–12	Xu et al. (2020)
Town, Sinan County,	2nd segment of antennular	segment
Guizhou Province,	peduncle
China
Caridina songtaoensis *	Guizhou Province,	Exceeding distal margin of	Not reaching to distal end of basal	2–4 (usually2–	16–19	Liang (2004)
China	basal antennular segment or	segment of antennular peduncle	3)+5–11/3–5
reaching to middle of second
segment
Caridina spinicrus *	Beiliu County,	Straight, reaching anterior	Reaching 0.7 basal segment length of	7+10/1	13	Cai & Ng (2018)
Guangxi Province,	half of second segment of	antennular peduncle
China	antennular peduncle,

......Continued on the next page TABLE 2 . (Continued)

Species	Locality	Rostrum length	Stylocerite	Rostrum formula	Spiniform	Reference
Caridina tetrazona *	Guizhou Province,	Nearly reaching to or slightly	Mostly reaching beyond the end of basal	3–8 (usually 5–	18–20	Chen et al.
China	reaching beyond end of	segment, sometimes to the middle of	7)+4–6/1–2	(2020)
1st segment of antennular	second segment of antennular peduncle
peduncle
Caridina thachlam	Northern Vietnam	Never reaching beyond	Not reaching to distal end of basal	0–1/0–1	9	Do et al.
end of basal segment of	segment of antennular peduncle	(2021b)
antennular peduncle
Caridina tricincta	Northern Vietnam	Reaching to middle or	Reaching distal end of basal segment of	0–3+0–6/0–5	12–18	Do et al. (2020)
slightly falling short of distal	antennular peduncle
end of basal segment of
antennular peduncle
Caridina trifasciata	Henquin Island near	Reaching near to end of	Reaching beyond end of basal segment	4+7–10/1–4	18–20	Yam & Cai
Zhuhai, Guangdong	second segment of antennular	of antennular peduncle, not extending to	(2003)
Province & Hong	peduncle, or slightly beyond	middle of second segment
Kong, China	it
Caridina venusta	Yingde County,	Only reaching to mid or often	Slightly beyond basal segment of	0/0	21–24	Wang et al.
Guangdong Province,	to end of eyes, occasionally	antennular peduncle	(2008)
China	extending to near distal end
of 1 st segment of antennular
peduncle
Caridina yunnanensis	Yunnan Province,	Reaching to second segment	Not reaching distal end of basal segment	5–7+4–12/2–8	13–14	Liang (2004)
China	of antennular peduncle	of antennular peduncle

Note: Rostrum formula is presented as: number of dorsal teeth on the carapace posterior margin of orbital margin + number of dorsal teeth on the rostrum anterior to the orbital margin/number of ventral teeth of the rostrum; Spiniform setae are on uropodal diaeresis;*: species without 16S rRNA sequence data. Coloration . Body semi-translucent, light grey with red dots on the carapace ( Fig. 3B ). Habitat . This species was found in a stream with mixed sand, mud, gravel, and rock substratum, and clear flowing water from the forest ( Fig. 3A ). Molecular results . The aligned 16S rRNA sequence dataset consisted of 541bp. The 16S rRNA sequences of the four individuals of Caridina danxiaensis sp. nov. from Danxia Mountain National Nature Reserve were identical. The interspecific pairwise genetic distances between Caridina danxiaensis (n = 4) and 28 morphologically/ genetically similar or closely distributed Caridina species varied from 0.057 ( Caridina clinata ) to 0.13 ( Caridina lanceifrons ) ( Table 1 ), clearly supporting C. danxiaensis sp. nov. as a distinct taxon. Etymology . The new species is named after Danxia Mountain National Nature Reserve located in Renhua County, Guangdong Province , China . The name Danxia also refers to various landforms found in southeast, southwest, and northwest China and consisting of a red bed with steep cliffs. This is a unique type of petrographic geomorphology. Chinese name: 丹AEẊợ (dân xiá mǐ xiâ), meaning Danxia shrimp. Remarks. Caridina danxiaensis sp. nov. shows some morphological similarities to C. baoting Cai, 2014 , C. caobangensis Li & Liang, 2002 , C. clinata Cai, X.Q. Nguyên & Ng, 1999 , C. conghuensis Klotz & von Rintelen, 2014 , C. cucphuongensis Dang, 1980 , C. haivanensis Do & Dang, 2010 , C. macauensis Zhou, Zhang, Wong & Huang, 2021 , C. pacbo Do, von Rintelen & Dang, 2020 , C. pingi Yü, 1938 , C. pseudoserrata , Dang & Do, 2007 , C. rubropunctata Dang & Do, 2007 , C. serrata Stimpson, 1860 , C. songtaoensis Liang, 2004 , C. tetrazona Chen, Chen, Zheng & Guo, 2020 , and C. tricincta Do, von Rintelen & Dang, 2020 by possessing a short rostrum. However, the remarkable feature of the short and slender, dorsally armed but ventrally unarmed rostrum of the new species is unusual for the genus Caridina . Caridina danxiaensis sp. nov. can be easily distinguished from these species by the characters shown in Table 2 . Cardina cuphuongensis , C. pacbo and C. serrata sometimes also lack ventral rostral teeth and there are overlaps in the rostrum formula and number of spiniform setae at the uropodal diaresis in these species with the new species. However, the stylocerite of C. danxiaensis sp. nov. merely reaches beyond distal end of basal segment of antennular peduncle, never reaching the middle of second segment of antennular peduncle, while that of C. cuphuongensis is much longer than the new species, reaching to the distal end of second segment of antennular peduncle or at least 0.7 times of it. Caridina pacbo and C. serrata bear a short rostrum never reaching to midlength of second segment of antennular peduncle, while that of Caridina danxiaensis sp. nov. reaching to midlength of second segment of antennular peduncle. According to the 16SrRNA sequence analyses, Caridina danxiaensis sp. nov. is closely related to C . clinata , C . rubropunctata , and C . trifasciata . Morphologically, C . clinata , and C . danxiaensis sp. nov. share a short rostrum, but the uropodal diaeresis of C. clinata bears much fewer (14–17) movable spiniform setae. The length of the stylocerite of C . rubropunctata and C . trifasciata is similar to the new species. However, the ventral margin of C. rubropunctata and C. trifasciata is armed with teeth. Overall, C . danxiaensis sp. nov. differs morphologically from the three species and other congeners by a relatively short rostrum just reaching to the midlength of the second segment of the antennular peduncle with rostral formula of 5–8+7–8/0, stylocerite reaching end of basal segment of antennular peduncle, and uropodal diaeresis with 19–23 movable spiniform setae.