Caridina cucphuongensis Dang, 1980

Yen, Phan Thi, Klotz, Werner, Rintelen, Thomas von, Dong, Dang Van & Tu, Do Van, 2021, REDESCRIPTION OF Caridina cucphuongensis Dang, 1980 (CRUSTACEA: DECAPODA: ATYIDAE) FROM CUC PHUONG NATIONAL PARK, NORTHERN VIETNAM, Academia Journal Of Biology 43 (4), pp. 45-54 : 47-53

Caridina cucphuongensis Dang, 1980 ( Figs. 2–4 )

Caridina serrata cucphuongensis Dang in Dang, Thai & Pham, 1980: 404–405; Fig. 230. [type locality: streams in Cuc Phuong area, Ninh Binh province, Northern Vietnam].

Caridina cucphuongensis Dang, 1980 in Dang & Ho, 2012: 116–117; fig.: 37.

Examined material

Neotype: male, cl 4.1 mm, IEBR-FS 006 , Vietnam, Ninh Binh, Cuc Phuong National Park, a small stream near the footpath to the one thousand year old tree (Vietnamese name: chò), 20 o 21’0.779’’N - 105 o 36’11.675’’E, coll. Thomas von Rintelen & Do Van Tu, 4 March 2017.

Other material: 5 males, cl 3.6–4.1 mm, 2 females, cl 4.2 and 4.4 mm, ZMB 30234 , same data as neotype; 2 males cl 3.0 and 4.0 mm, 4 females cl 4.2–5.3 mm, 2 ovigerous females cl 4.6 and 4.8 mm, ZMB 31774 , Vietnam, Ninh Binh, Cuc Phuong National Park, a stream on footpath Bong , 20 o 21’33.2”N - 105 o 34’49.0”E, coll. Thomas von Rintelen, 7 May 2019; male, cl 3.8 mm, ZMB 31782 , Vietnam, Ninh Binh, Cuc Phuong National Park, a stream near Bong , 20 o 20’48.0”N - 105 o 36’23.0”E, coll. Hoang Anh Tuan, 8 May 2019; ZMB 30752 , Vietnam, Ninh Binh, Cuc Phuong National Park, a stream on footpath Bong , Khanh village , 20 o 21’33.2”N - 105 o 34’49.0”E, coll. Andreas Karge, 12 July 2009; ZMB 31776 , Vietnam, Ninh Binh, Cuc Phuong National Park, a stream near Bong , limestone terraces , 20 o 21’18.8”N - 105 o 35’22.4”E, coll. Sarah Ehlers, 10 May 2019.

Comparative material

Caridina clinata Cai, Nguyen & Ng, 1999: 2 males, cl 3.1 and 3.6 mm, ovigerous female, cl 3.7 mm, ZMB 30664, Vietnam, Ninh Binh, a small stream in Cuc Phuong National Park, 20 o 19’11.118’’N - 105 o 37’42.168’’E, coll. Thomas von Rintelen & Do Van Tu, 4 March 2017. Caridina pacbo Do, von Rintelen & Dang, 2020 : male, cl 4.2 mm, IEBR–FS 003 (Holotype), Vietnam, Cao Bang province, Ha Quang District, Truong Ha Commune, Pac Bo Village, small stream in Khuoi Nam, 22 o 59’1.7”N - 106 o 02’31.2”E, coll. Do Van Tu, 25 May 2017. Caridina tricincta Do, von Rintelen & Dang, 2020 : male, cl 5.3 mm, IEBR–FS 001 (Holotype), Vietnam, Tuyen Quang Province, Na Hang District, Khau Tinh Commune, 22 o 26’42.1”N - 105 o 23’09.1”E, coll. Nguyen Anh Tuan, 11 December 2012. Caridina serrata Stimpson, 1860: 10 males, cl 3.1–4.7, 5 females, cl 4.0– 4.6, ZMB 30306, Vietnam, Quang Nam Province, Hoi An City, Cu Lao Cham Island, a small stream running into the reservoir, 15 o 56’34.9”N - 108 o 31’22.7”E, coll. Pham The Cuong, 10 May 2017.

Description

Cephalothorax and cephalic appendages

Carapace length 3.0–5.3 mm (median 4.1 mm, n = 16). Rostrum straight, rather slender, just overreaching the eyes to reaching to the beginning of second segment of antennular peduncle, 0.28–0.29 (median 0.29) times as long as carapace, rostral formula: 0–3+2–7/0–2, ventral teeth placed distally. Suborbital angle acute, completely fused with antennal spine; pterygostomian margin rounded, slightly produced forward ( Fig. 2A ).

Eyes well developed with globular cornea, anterior end reaching to 0.6 times length of basal segment of antennular peduncle ( Fig. 2A ). Antennular peduncle 0.55–0.65 (median 0.61) times as long as carapace; basal segment 1.67–2.0 (median 1.77) times as long as second segment, second segment 1.3–1.5 (median 1.5) times as long as third segment ( Fig. 2B ). Stylocerite reaching to the beginning of second segment of antennular peduncle ( Fig. 2B ). Scaphocerite rather angular, reaching beyond distal end of antennular peduncle, lateral tooth not reaching beyond distal margin, 2.5–2.93 (median 2.87) times as long as wide ( Fig. 2C ).

Abdominal somites, telson and uropods

Sixth abdominal somite 0.45–0.5 (median 0.48) times length of carapace, 1.46–1.64 (median 1.55) times as long as fifth abdominal somite, 0.85–0.95 (median 0.93) times length of telson. Telson length 2.0–2.33 (median 2.2) times as long as proximal wide, distal margin triangular, terminating in a short median projection, with 4–5 pairs of dorsal spiniform setae and one pair of dorso-subdistal spiniform setae; distal end with 3–4 pairs of spiniform setae, lateral pair longer than intermediate pairs, sublateral pair shortest ( Figs. 2D, 2E ). Preanal carina round, slightly bent backwards, with few setae, lacking a spine ( Fig. 2F ). Uropodal diaeresis with 18– 21 (median 20) movable spiniform setae, outermost one slightly longer than lateral angle ( Fig. 2G ).

Incisor process of mandible ending in one row of 6–8 irregular teeth, molar process truncated ( Fig. 2H ). Lower lacinia of maxillula broadly rounded, upper lacinia elongated, with number of distinct teeth and setae on inner margin, palp stout with few simple setae at tip ( Fig. 2I ). Upper endites of maxilla subdivided, palp short, scaphognathite tapering posteriorly, with numerous long, curved setae at posterior margin ( Fig. 2J ). Distal end of palp of first maxilliped triangular, with a short projection; flagellum of the exopod very elongated, endopod high, reaching 0.9 times length of flagellum of exopod ( Figs. 2K, 2L ). Podobranch of second maxilliped well developed, with finger-like projections ( Fig. 2M ). Third maxilliped reaching to distal end of antennular peduncle, ending in single terminal claw, exopod reaching 0.3 times length of penultimate segment; ultimate segment as long as penultimate segment ( Fig. 2N ).

Pereiopods

Epipods present on first four pereiopods. First pereiopod short, robust, reaching beyond end of basal segment of antennular peduncle; chela 2.0–2.23 (median 2.09) times as long as wide, 1.25–1.47 (median 1.3) times length of carpus; tips of fingers rounded, without hook; dactylus shorter than palm, 0.57–0.96 (median 0.92) times as long as palm; carpus excavated strongly anteriorly, 1.46–1.89 (median 1.71) times as long as wide, 0.90–0.95 (median 0.92) times length of merus; merus 2.29–2.86 (median 2.56) times as long as wide, longer than ischium ( Fig. 3A ). Second pereiopod long, slender, reaching to distal end of antennular peduncle; chela 2.56–3.0 (median 2.78) times as long as wide, 0.66–0.85 (median 0.74) times length of carpus; tips of fingers rounded, without hook; dactylus 1.33– 1.74 (median 1.43) times as long as palm; carpus 4.83–5.83 (median 5.67) times as long as wide, 0.94–1.11 (median 1.02) times as long as merus; merus 5.64–6.8 (median 6.30) times as long as wide, longer than ischium ( Fig. 3B ). Third pereiopod slender, reaching beyond end of scaphocerite by its dactylus, terminating in one claw, with five to six accessory spiniform setae on flexor margin, dactylus 2.54–3.08 (median 2.86) times as long as wide (terminal claw and spiniform setae on flexor margin included), propodus 7.65–9.38 (median 8.75) times as long as wide, 3.51–3.94 (median 3.68) times as long as dactylus; carpus 4.9–5.05 (median 5.02) times as long as wide, 0.72–0.85 (median 0.78) times as long as propodus, 0.55–0.6 (median 0.58) times as long as merus; merus 6.07–7.08 (median 6.64) times as long as wide, bearing four strong, movable spiniform setae on posterior margin of outer surface; ischium without movable spiniform seta ( Figs. 3C, 3D ). Fifth pereiopod slender, reaching to end of second segment of antennular peduncle, dactylus 3.3–3.9 (median 3.5) times as long as wide (terminal claw and spiniform setae on flexor margin included), terminating in one large claw, with 42–52 spiniform setae on flexor margin; propodus 11.23–12.67 (median 11.43) times as long as wide, 2.90– 3.41 (median 3.20) times length of dactylus; carpus 4.63–5.8 (median 5.11) times as long as wide, 0.48–0.56 (median 0.55) times as long as propodus, 0.5–0.62 (median 0.56) times as long as merus; merus 6.64–7.5 (median 7.22) times as long as wide, bearing 3–4 strong, movable spiniform setae on posterior margin of outer surface; ischium without movable spiniform seta ( Figs. 3E, 3F ).

Pleopods

Endopod of male first pleopod extending to 0.6 times length of exopod, subrectangular in shape, anterior part not folded backwards, 2.5–2.82 (median 2.8) times as long as proximal width, 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 0.4 of its length ( Figs. 3G, 3H ). Appendix masculina of male second pleopod slender, reaching to proximal 0.7 times endopod length, 7.9 times as long as distal width, stick-shaped, slightly widened distally with some short spiniform setae on outer surface and some long spiniform setae on distal surface; appendix interna at middle of appendix masculina, narrow, small, extending about 0.4 times length of appendix masculina ( Figs. 3I, 3J ).

Reproductive biology

Two ovigerous females, ZMB 31774, cl 4.6 and 4.8 mm, undeveloped eggs 1.08 × 0.72 mm, eggs with eyespots 1.23 × 0.81 mm, ovigerous female with eyespots carries 23 eggs.

Coloration

The body is yellowish to grey and dark grey in color. Dark grey spots present, sometimes look like as transverse stripes ( Fig. 4 ).

Habitat

This species was found in the streamlets with mixed sand, gravel, and rock substrate, and clear water flowing from the natural forest ( Fig. 5 ).

REMARKS

Caridina cucphuongensis Dang, 1980 in Dang & Ho (2012) is characterized by several morphological characters such as short rostrum with large teeth on dorsal margin, long stylocerite, subrectangular endopod of male first pleopod, and short appendix interna of male second pleopod. However, the branchial formula of this species does not the same as that of generally found in Caridina but it is more similar to those of Paracaridina Liang, Guo & Tang, 1999 (5 pairs of well developed pleurobranchs; 2 pairs of arthrobranchs on third maxillipeds, with second pair strongly reduced in size; 1 pair of well developed podobranch on the second maxilliped, arthrobranch absent on the first pereiopod, epipods well developed on third maxillipeds and the first four pereiopods). This character, however, is not unique to Paracaridina (von Rintelen et al., 2008) . Moreover, there is weak support from genetic analysis to put this species under the genus Paracaridina (Do et al., 2021a) . Therefore, we have retained this species under the genus of Caridina .

Caridina cucphuongensis somewhat resembles C. serrata Stimpson, 1860 , C. clinata Cai, Quynh & Ng, 1999 , C. tricincta Do, von Rintelen & Dang, 2020 and C. pacbo Do, von Rintelen & Dang, 2020 by possessing a short rostrum and the shape of endopod of male first pleopod. However, C. cucphuongensis can be easily distinguished from these species by the characters shown in Table 1 .

Conservation status

We have conducted many surveys and collected samples of atyid shrimp across Vietnam. However, so far this species has only been found in a few streamlets in the Cuc Phuong National Park. With a very narrow distribution, according to IUCN Red List Categories and Criteria (IUCN, 2019), this species could be classified as endangered if any threats should emerge. Good protection of forest cover as well as limiting impacts that can cause water pollution are important measures to conserve this species.

Figures

Figure 2. Caridina cucphuongensis Dang, 1980; male, cl 4.1 mm (ZMB 30234). 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: A–C, F = 1 mm; E, G–N = 0.5 mm

Figure 3. Caridina cucphuongensis Dang, 1980; male, cl 4.1 mm (ZMB 30234). 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: A–J = 0.5 mm

Figure 4. Caridina cucphuongensis Dang, 1980, in situ photograph

Figure 5. Habitat of Caridina cucphuongensis Dang, 1980 in Cuc Phuong National Park.