Caridina stellata, Guo & Chen & Chen & Cai & Guo, 2022

Guo, Guo-Cai, Chen, Qing-Hua, Chen, Wen-Jian, Cai, Chao-Huang & Guo, Zhao-Liang, 2022, Caridina stellata, a new species of atyid shrimp (Decapoda, Caridea, Atyidae) with the male description of Caridina cavernicola Liang & Zhou, 1993 from Guangxi, China, ZooKeys 1104, pp. 177-201 : 177

Caridina stellata sp. nov.

Figs 2 , 3 , 4A, E

Material examined.

Holotype: male (FU, 2018-11-05-01), cl 5.4 mm, tl 20.8 mm, rl 2.6 mm, a stream near Liuchacun , Jinxiu Town , Jinxiu Yao Autonomous County, Laibin City , Guangxi Zhuang Autonomous Region, China (24°3'59.63"N, 110°17'43.94"E, alt. 622 m), 5 November 2018 . Paratype: male (FU, 2018-11-05-02), cl 5.3 mm, Paratypes: 15 males (FU, 2018-11-04-03), cl 5.0- 6.2 mm; Paratypes: 29 females (FU, 2018-11-05-04), cl 4.9-6.6 mm, same collection data as for holotype .

Paratypes: 17 males (FU, 2019-03-20-01), cl 4.7-6.8 mm, three females (FU, 2019-03-20-02), cl 4.5-7.4 mm, a stream near Daxincun , Jinxiu Yao Autonomous County, Laibin City , Guangxi Zhuang Autonomous Region, China (23°57'52.77"N, 110°15'10.91"E, alt. 741 m), 20 March 2019 .

Paratypes: Four males (FU, 2019-03-19-01), cl 4.7-6.8 mm, 34 females, one ovigerous (FU, 2019-03-19-02), cl 4.5-7.4 mm, a stream near Jiajiangcun , Jinxiu Yao Autonomous County, Laibin City , Guangxi Zhuang Autonomous Region, China (24°11'13.18"N, 110°8'36.79"E, alt. 839 m) . 19 March 2019.

Paratypes: 31 males (FU, 2019-03-19-03), cl 4.7-6.8 mm, 12 females (FU, 2019-03-19-04), cl 4.5-7.4 mm, a stream near Liupai , Jinxiu Yao Autonomous County, Laibin City , Guangxi Zhuang Autonomous Region, China (24°12'12.76"N, 110°8'25.78"E, alt. 510 m), 19 March 2019 .

Paratypes: 10 males (FU, 2018-11-26-01), cl 4.7-6.8 mm, seven females (FU, 2018-11-26-02), cl 4.5-7.4 mm, a stream of Lotus Hill Scenic Spot , Dahua Yao Autonomous County, Hechi City , Guangxi Zhuang Autonomous Region, China (24°3'8.12"N, 107°38'30.5"E, alt. 350 m), 26 November 2018 .

Comparative material.

Caridina cantonensis : 10 females (cl: 4.8-6.9 mm), eight males (cl: 5.5-6.5 mm), Zaomushan , Foshan City, Guangdong Province (22°44'22"N, 112°46'36"E, alt. 56 m), 17 May 2018 .

Caridina serrata : 17 females (CL: 3.3-6.7 mm), three ovigerous females (CL: 3.9-5.7 mm), 17 males (CL: 2.8-5.3 mm), Dong'ao Village , Dong'ao Island , Zhuhai City, Guangdong Province (22°01'12"N, 113°42'26"E, alt. 8.4 m), 23 August 2014 .

Diagnosis.

Rostrum long, straight, slightly sloping downwards, reaching to end of 2nd segment of antennular peduncle, occasionally reaching to end of 3rd segment of antennular peduncle; rostral formula 6-8+7-16/6-13. 1st pereiopod carpus 0.43-0.71 × as long as chela, 1.2-1.4 × as long as high; chela 1.8-2.4 × as long as broad; fingers 0.80-1.1 × as long as palm. 2nd pereiopodcarpus 1.1-1.3 × as long as chela, 4.0-4.8 × as long as high; chela 2.1-2.4 × as long as broad; fingers 1.1-1.4 × as long as palm. 3rd pereiopod propodus 4.0-5.5 × as long as dactylus, with two rows thin spines on the posterior margin, ischium with one spine on the posterior margin. 5th pereiopod propodus 4.2-5.3 × as long as dactylus, with two rows of thin spines on the posterior and lateral margins, dactylus terminating in one claw, with 35-40 spinules on flexor margin. Endopod of male 1st pleopod extending to 0.68 × exopod length, wider proximally, rectangle, about 3.7-3.9 × as long as wide, appendix interna well developed, arising from distal 1/6 of endopod, reaching end of endopod. Appendix masculina of male 2nd pleopod cylindrical, reaching to 0.58 length of endopod, appendix interna reaching to 0.50 length of appendix masculina. Uropodal diaeresis with 17-19 movable spinules. Eggs 0.84-0.89 × 1.27-1.39 mm in diameter.

Description.

Body: slender and sub-cylindrical, males up to 30.7 mm tl, females up to 32.5 mm tl.

Rostrum (Fig. 2A ): Long, straight, slightly sloping downwards, reaching to end of 2nd segment of antennular peduncle, occasionally reaching to end of 3rd segment of antennular peduncle; 0.39-0.48 of cl; armed dorsally with 13-24 teeth, including 6-9 on carapace posterior to orbital margin, ventrally with 6-13 teeth; rostrum formula 6-9+7-15/6-13; lateral carina dividing rostrum into two unequal parts, continuing posteriorly to orbital margin.

Eyes (Fig. 2A ): Well developed, on short ocular peduncle, cornea globular.

Carapace (Fig. 2A ): Smooth, glabrous; antennal spine acute, fused with inferior orbital angle; pterygostomian margin rectangular, pterygostomian spine absent.

Antennule (Fig. 2B ): Peduncle reaching slightly short of scaphocerite; stylocerite long, reaching 0.40 of 2nd segment; anterolateral angle reaching 0.40 of 2nd segment; basal segment as long as combined length of 2nd and 3rd segments, 2nd segment about 0.60 of 1st segment, about 1.6 of 3rd segments; all segments with marginal plumose setae.

Antenna (Fig. 2C ): Peduncle about 0.40 × as long as scaphocerite; scaphocerite about 3.5 × as long as wide, outer margin straight, asetose, ending in a strong sub-apical spine, inner and anterior margins with long plumose setae.

Mandible (Fig. 2D ): Without palp; left incisor process with five sharp teeth; two groups of setae medially; molar process ridged.

Maxillula (Fig. 2E ): Lower lacinia broadly rounded, with several rows of plumose setae; upper lacinia elongate, medial edge straight, with 20-26 strong spinules and simple setae; palp simple, slightly expanded distally, with seven long simple setae.

Maxilla (Fig. 2F ): Scaphognathite tapers posteriorly, distally with regular row of long plumose setae and short marginal plumose setae continuing down proximal triangular process, furnished with numerous long plumose setae; upper and middle endite with marginal simple, denticulate and submarginal simple setae, distally with plumose setae; lower endite with long simple marginal setae; palp slightly shorter than the cleft of upper endite, wider proximally than distally, setose.

First maxilliped (Fig. 2G ): Palp broadly triangular ending in fringe-like tip and with terminal plumose setae; caridean lobe broad, with marginal plumose setae; exopodal flagellum well developed, with distally marginal plumose setae; ultimate and penultimate segments of endopod indistinctly divided; medial and distal margins of ultimate segment with marginal and sub-marginal rows of simple, denticulate and plumose setae; penultimate segments with marginal long plumose setae.

Second maxilliped (Fig. 2H ): Ultimate and penultimate segments of endopod indistinctly divided, reflected against basal segment; inner margin of ultimate, penultimate and basal segments with long setae of various types; exopod flagellum long, slender with marginal plumose setae distally.

Branchial formula typical for genus.

Third maxilliped (Fig. 3A ): Reaches middle of 3rd antennular peduncle segment, endopod three-segmented, penultimate segment as long as basal segment; distal segment 1.1 × as long as penultimate segment, ending in a large claw-like spine surrounded by simple setae, preceded by 12 spines with double arrangement along distal third of posterior margin, a clump of long and short simple, serrate setae proximally; exopod reaches to end of basal segment of endopod, distal margin with long plumose setae.

First pereiopod (Fig. 3B ): Reaches about end of eye; chela 1.8-2.4 × as long as high; 1.4-2.3 × length of carpus; movable finger 2.4-2.8 × as long as wide, 0.80-1.1 × length of palm, setal brushes well developed; carpus excavated disto-dorsally, 1.2-1.4 × as long as wide, 0.85-1.0 × length of merus.

Second pereiopod (Fig. 3C ): Reaches about end of 2nd antennular peduncle segment, more slender and longer than first pereiopod; chela 2.1-2.4 × as long as high; 0.76-0.94 × length of carpus; movable finger 3.4-4.9 × as long as wide and 1.1-1.4 × as long as palm, setal brushes well developed; carpus 4.0-4.8 × as long as wide, slightly excavated distally, about 1.1 × length of merus.

Third pereiopod (Fig. 3D ): Reaches beyond end of scaphocerite; dactylus 2.0-2.9 × as long as wide, ending in prominent claw-like spine surrounded by simple setae, behind which are 4-5 spines; propodus 4.0-5.5 × length of dactylus, bearing two rows of thin spinules on posterior and lateral margin, 8.0-9.9 × as long as wide; carpus 0.57-0.70 × length of propodus; merus 1.7-2.4 × length of carpus, with about 3-4 strong spines on the posterior margin; ischium with a spine on the posterior margin.

Fifth pereiopod (Fig. 3E ): Reaches middle of 2nd segment of antennular peduncle; dactylus 1.7-3.0 × as long as wide, ending in prominent claw-like spine surrounded by simple setae, behind which is a comb-like row of 35-40 spines; propodus 4.2-5.3 × length of dactylus, bearing two rows of spinules on posterior and lateral margins, 9.1-13.0 × as long as wide; carpus 0.43-0.58 × length of propodus; merus 1.4-1.5 × length of carpus, with about 3-4 strong spines on the posterior margin.

First four pereiopods with epipod.

First pleopod (Figs 3F and H ): Endopod in male is rectangle, about 0.70 × length of exopod, about 3.7-3.9 × as long as proximally wide, tip rounded, inner margin concave, bearing nearly equal spine setae, outer margin bearing nearly equal long and dense spine setae, distally absent (Fig. 3F ) or bearing a few sparse thin spine setae (Fig. 3H ); appendix interna well developed, arising from distal 1/5 of endopod, reaching to end of endopod, with cincinuli distally.

Second pleopod (Fig. 3G ): Appendix masculina rod-shaped, reaching about 0.60 × length of exopod, inner margin bearing and tip bearing nearly equally long and stout spine setae; appendix interna well developed, reaching about 0.50 × length of appendix masculina, with many cincinuli distally.

Telson (Fig. 3I ): 0.42-0.55 × length of cl, distinctly longer than sixth abdominal segment, tapering posteriorly, with a projection, dorsal surface with six pairs of stout movable spine setae including the pair at posterolateral angles; posterior margin with four pairs of intermedial plumose setae, the outer one usually strongest and longest. Exopodite of the uropod bears a series of 17-19 movable spinules along the diaresis.

Eggs 0.84-0.89 × 1.27-1.39 mm in diameter.

Colouration.

Body semi-transparent, light reddish-brown colour, with small red pigment spots scattered on whole body, several large red-brown dots on the tergum and the posterior margin of the carapace, red-brown vertical stripes on topside of the 1st and 2nd pleon and lower lateral side of 1st, 3rd, 4th and 5th pleon and carapace; appendages transparent, with red-brown stripes in the distal part of each segment; telson and tail fan bright red (Fig. 4A )

Etymology.

Caridina stellata is named after the Latin word stellatus, for dots, alluding to the pigmented pattern of the body.

Remarks.

Caridina stellata sp. nov. clearly belongs to the " Caridina serrata group" of the genus and shows a strong morphological similarity with C. cantonensis Yu, 1936 in shape and indentation of the rostrum. Caridina stellata sp. nov. can be distinguished from C. cantonensis by the broad palp of the 1st maxilliped with a finger-like tip (versus without a finger-like tip in C. cantonensis ); rostrum with more ventral teeth (6-13 versus 2-6 in C. cantonensis ); the stouter carpus of the 1st pereiopod (1.2-1.4 times as long as wide versus 1.5-1.7 in C. cantonensis ); the slender endopod of the 1st male pleopod, about 3.7-3.9 × as long as wide, wider proximally (versus 2.5-3.0, wider terminally in C. cantonensis ); completely different shape of the appendix masculina of male 2nd pleopod (Fig. 3G versus fig. 87r in Liang 2004); and relatively larger eggs, size of developed eggs 0.84-0.89 × 1.27-1.39 mm (versus 0.63-0.72 × 0.99-1.09 mm in C. cantonensis ). In addition, its distinctive colouration and patterns easily separate the two species when observed in the field.

Caridina stellata sp. nov. resembles C. pacbo Do, von Rintelen & Dang, 2020 in colouration and pattern and also in the long stylocerite. Moreover, the type locality, Cao Bang Province, Vietnam, is close to Guangxi, China. However, the new species can be distinguished from C. pacbo by the longer rostrum, reaching end of 2nd segment of antennular peduncle, 0.39-0.48 of cl (versus close to end of 1st segment, 0.25-0.36 of cl in C. pacbo ), with more ventral teeth (6-13 teeth versus 0-3 in C. pacbo ); the stouter carpus of the 1st pereiopod (1.2-1.4 times as long as wide versus 1.3-1.7 in C. pacbo ); the stouter chela of the 2nd pereiopod (2.1-2.4 times as long as wide versus 2.7-3.1 in C. pacbo ) with carpus as long as the merus (versus longer than merus in C. pacbo ); and the slender endopod of the 1st male pleopod (3.7-3.9 × as long as wide versus 2.9-3.3 in C. pacbo ).

Caridina stellata sp. nov. also looks similar to C. multidentata Stimpson, 1860 in the colouration and pattern of live individuals. C. stellata can be easily distinguished from C. multidentata by the longer stylocerite, reaching 0.40 of the 2nd segment of the antennular peduncle (versus 0.70 of the 1st segment of antennular peduncle in C. multidentata ); with straight rostrum (versus with a crest over orbit in C. multidentata ), more teeth on carapace posterior to orbital margin (6-9 teeth versus 0 in C. multidentata ); and large eggs (0.84-0.89 × 1.27-1.39 mm versus 0.23-0.28 × 0.38-0.40 mm in C. multidentata ).

Ecological notes.

Caridina stellata appears to be a common atyid species in Guangxi. It was found from four streams in the Jinxiu Yao Autonomous County, Laibin City and also found in Dahua Yao Autonomous County, Hechi City. The environment of the streams is very similar. The streams run through land that is covered by secondary forest, with rocks interspersed with patches of gravel at the bottom (Fig. 4E ). The width and depth of the streams were 2.0-3.5 m and 0.3-1.0 m, respectively, with waterfalls and rapids present. The shrimps inhabit vegetation amidst running water, under rocks in lentic environments and even in stagnant water, such as shallow pools. C. stellata was found at Jinxiu, in co-existence with the atyid, Neocaridina palmata ( Shen 1948) and the palaemonid Macrobrachium nipponense . At Dahua, this species was found also living together with N. palmata . The majority of the habitats surveyed had a relatively high density of the new species.

Distribution.

Known from Guangxi Zhuang Autonomous Region, southwest China.

Figures

Figure 2. Caridina stellata sp. nov. A carapace and cephalic appendages, lateral view B antennule C antenna D mandible E maxillula F maxilla G first maxilliped H second maxilliped. Scale bars: 1.0 mm (A); 0.5 mm (B-C); 0.2 mm (D-H).

Figure 3. Caridina stellata sp. nov. A third maxilliped B first pereiopod C second pereiopod D third pereiopod E fifth pereiopod F, H first male pleopod G second male pleopod I telson. Scale bars: 0.5 mm (A-E, I); 0.2 mm (F-H).

Figure 4. Habitats and live colouration of Caridina stellata sp. nov. and C. cavernicola A C. stellata sp. nov. B-D C. cavernicola; E-H surrounding environment of C. stellata sp. nov (E) and C. cavernicola (F-H).