Caridina tetrazona, Chen & Chen & Zheng & Guo, 2020

Chen, Qing-Hua, Chen, Wen-Jian, Zheng, Xiao-Zhuang & Guo, Zhao-Liang, 2020, Two freshwater shrimp species of the genus Caridina (Decapoda, Caridea, Atyidae) from Dawanshan Island, Guangdong, China, with the description of a new species, ZooKeys 923, pp. 15-32 : 15

Caridina tetrazona sp. nov. Figs 2A , 3A , 4 , 5

Material examined.

Holotype: male (FU, 2017-06-27-01), cl 3.9 mm, tl 14.4 mm, rl 1.3 mm, a stream near Longtangzui Dawanshan Island, Zhuhai City, Guangdong, China (21°56'59.2"N, 113°43'00"E, al. 8 m, stn 1), 9 June 2017. Paratypes: male (FU, 2017-06-27-02), cl 4.3 mm, 4 males (FU, 2017-06-27-03), cl 3.8-4.3 mm, 33 females, 4 ovigerous (FU, 2017-06-27-04), cl 3.8-5.4 mm, same collection data as for holotype, coll. Z. L. Guo, W. J. Chen.

Comparative material.

Caridina serrata Stimpson, 1860 (see material under Caridina serrata ). Caridina cantonensis Yu, 1938; 8 males, cl 3.5-6.3 mm, 5 females, 2 ovigerous, cl 4.1-6.3 mm, a stream at Mangzixia, Yingde, Qingyuan City, Guangdong, China (24°3'20"N, 113°19'6" E, al. 20 m), 4 June 2018, coll. Z. L. GUO, W. J. Chen, X. Z. Zheng.

Diagnosis.

Rostrum short, straight or slightly sloping downwards, nearly reaching to or slightly reaching beyond end of 1st segment of antennular peduncle, rostral formula 3-8 (usually 5-7) + 4-6/1-2. 1st pereiopod carpus 0.63-0.70 × as long as chela, 1.6-1.7 × as long as high; chela 1.8-2.0 × as long as broad; fingers 0.92-1.1 × as long as palm. 2nd pereiopod carpus 1.1-1.3 × as long as chela, 4.9-5.3 × as long as high; chela 2.7-2.9 × as long as broad; fingers 1.7-1.8 × as long as palm. 3rd pereiopod propodus 3.9-4.5 × as long as dactylus, with 8-11 thin spines on the posterior and lateral margins. 5th pereiopod propodus 4.9-5.1 × as long as dactylus, with 8-11 thin spines on the posterior and lateral margins, dactylus terminating in one claw, with 27-31 spinules on flexor margin. Endopod of male 1st pleopod extending to 0.56 × exopod length, wider proximally, subrectangular, 2.5-2.6 × as long as wide, appendix interna well developed, arising from distal 1/3 of endopod, reaching beyond end of endopod. Appendix masculina of male 2nd pleopod rod-shaped, reaching to 0.7 length of endopod, appendix interna reaching to 0.7 length of appendix masculina. Uropodal diaeresis with 18-20 movable spinules. Eggs 0.51-0.65 × 0.84-0.97 mm in diameter.

Description.

Body: small, slender and sub-cylindrical, males up to 14.8 mm tl, females up to 20.4 mm tl.

Rostrum (Fig. 4A, B ): Short, only 0.15-0.32 of cl, straight or slightly sloping downwards; reaching end of basal segment of antennular peduncle, or to just beyond it; armed dorsally with 7-14 teeth, including 3-8 (usually 5-7) on carapace posterior to orbital margin, ventrally with 1-2 teeth; lateral carina dividing rostrum into two unequal parts, continuing posteriorly to orbital margin.

Eyes (Fig. 4A, B ): Well developed on short ocular peduncle, cornea globular.

Carapace (Fig. 4A, B ): Smooth, glabrous; antennal spine acute, fused with inferior orbital angle; pterygostomian margin broadly rounded or slightly produced forward; no pterygostomian.

Antennule (Fig. 4A-C ): Peduncle reaching slightly short of scaphocerite; stylocerite long, reaching 0.3 × of 2nd segment; anterolateral angle reaching 0.2 × of 2nd segment; length of basal segment as long as sum of length of 2nd and 3rd segments, 2nd segment 0.46-0.51 × of basal segment, 1.1-1.3 × of 3rd segment; all segments with sub-marginal plumose setae.

Antenna (Fig. 4D ): Peduncle about 0.54 × of scaphocerite; scaphocerite about 3.6 × as long as wide, outer margin straight, ending in strong sub-apical spine, inner and anterior margins with long plumose setae.

Mandible (Fig. 4E ): Without palp; left incisor process with 4 sharp teeth; medially 2 groups of setae; molar process ridged.

Maxillula (Fig. 4F ): Lower lacinia broadly rounded, with several rows of plumose setae; upper lacinia elongate, medial edge straight, with 29 strong spinules and simple setae; palp simple, slightly expanding distally, with 4 long simple setae.

Maxilla (Fig. 4G ): Scaphognathite tapering 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 sub-marginal simple setae, distally with plumose setae; lower endite with long simple marginal setae; palp distinctly shorter than cleft of upper endite, wider proximally than distally.

First maxilliped (Fig. 4H ): 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. 4I ): Ultimate and penultimate segments of endopod indistinctly divided, reflexed 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. Epipod on first four pereiopods.

Third maxilliped (Fig. 5A ): Reaches to end of 2nd antennular peduncle segment, endopod three-segmented, penultimate segment as long as basal segment; distal segment 0.87-0.90 × as long as penultimate segment, ending in a large claw-like spine surrounded by simple setae, preceded by about 5-8 spines on distal third of posterior margin, proximally a clump of long and short simple, serrate setae; exopod reaches to end of basal segment of endopod, distal margin with long plumose setae.

First pereiopod (Fig. 5B ): Reaches end of eyes; chela 1.8-2.2 × as long as wide; 1.4-1.6 × as long as carpus; movable finger 2.8-3.2 × as long as wide, 0.92-1.1 × as long as palm, setal brushes well developed; carpus excavated anterior-dorsally, 1.5-1.8 × as long as high, 0.90-1.0 × as long as merus.

Second pereiopod (Fig. 5C ): Reaches about end of 3rd antennular peduncle segment, more slender and longer than first pereiopod; chela 2.6-3.2 × as long as wide; 0.78-0.87 × as long as carpus; movable finger 4.0-4.6 × as long as wide and 1.5-1.7 × as long as palm, setal brushes well developed; carpus 4.9-5.9 × as long as high, slightly excavated anterior, as long as merus.

Third pereiopod (Fig. 5D ): Reaches beyond end of scaphocerite; dactylus 2.9-3.5 × as long as wide, ending in prominent claw-like spine surrounded by simple setae, flexor margin bearing 4-5 spines; propodus 4.5-4.9 × as long as dactylus, bearing 8-12 spinules on posterior and lateral margin, 8.4-9.7 × as long as wide; carpus 0.67-0.82 × as long as propodus; merus 1.7-2.0 × as long as carpus, with about 3-4 strong spines on the posterior margin.

Fourth pereiopod: Reaches middle of 2nd segment of antennular peduncle; dactylus 3.0-4.2 × as long as wide, ending in prominent claw-like spine surrounded by simple setae, flexor margin bearing 4-6 spines; propodus 4.2-5.1 × as long as dactylus, bearing 9-13 spinules on posterior and lateral margin, 8.5-10.5 × as long as wide; carpus 0.66-0.81 × as long as propodus; merus 1.6-1.8 × as long as carpus, with about 3-4 strong spines on the posterior margin.

Fifth pereiopod (Fig. 5E ): Reaches middle of 1st segment of antennular peduncle; dactylus 2.8-3.6 × as long as wide, ending in prominent claw-like spine surrounded by simple setae, flexor margin bearing with a row of 27-31 comb-like spinules; propodus 4.7-5.1 × as long as dactylus, bearing 8-11 spinules on posterior and lateral margin, 8.9-11.9 × as long as wide; carpus 0.52-0.62 × as long as propodus; merus 1.3-1.5 × as long as carpus, with about 3-4 strong spines on the posterior margin.

First pleopod (Fig. 5F ): Endopod of male subrectangular, wider proximally, 0.56 × as long as exopod, 2.5-2.6 × as long as proximal wide, ending broadly rounded; inner margin slightly concave, bearing short spine-like setae, outer margin slightly convex, bearing long spine-like setae, distinctly longer and stout on distal 1/3, distal end tip bearing nearly equal length shorter spine-like setae; appendix interna well developed, arising from distal 1/3 of endopod, reaching beyond end of endopod, distally with numerous cincinulli.

Second pleopod (Fig. 5G ): Appendix masculina rod-shaped, reaching about 0.7 × length of exopod, inner margin and tip bearing numerous spine setae; appendix interna slender, reaching about 0.73 × length of appendix masculina, distally with many cincinulli.

Telson (Fig. 5H ): 0.56-0.75 × as long as cl, tapering posterior, dorsal surface with 6 pairs of stout movable spine-like setae including the pair at poster lateral angles; posterior margin with 4-5 pairs of intermediate plumose setae, the outer one usually strongest and longest, no median projection on posterior margin. Exopodite of uropod bearing a series of 18-20 movable spinules on the diaeresis.

Eggs 0.51-0.65 × 0.84-0.97 mm in diameter.

Coloration: Body semi-translucent, four dark blue bands transverse on the tergum of the 1st, 3rd, 5th, and 6th abdominal segments, appendages mostly translucent (Fig. 3A ).

Etymology.

Caridina tetrazona is a combination of two Latin words, tetra, four, and zona, band, alluding to its four-banded color pattern.

Remarks.

Caridina tetrazona sp. nov. is most similar to C. serrata Stimpson, 1860 (which also occurs on the same island) in the short rostrum, the shape of the endopod of the male first pleopod, and the similar-sized eggs. It can be easily distinguished from C. serrata by the length of the basal segment of the antennular peduncle which is as long as the combined length of 2nd and 3rd segments (versus length of basal segment distinctly longer than the combined length of 2nd and 3rd segments in C. serrata ); length of penultimate segment of 3rd maxilliped as long as basal segment; the distal segment is distinctly shorter than the penultimate segment (versus penultimate segment distinct shorter than basal segment and distal segment as long as penultimate segment in C. serrata ); the absence of a projection on the posterior margin of telson (versus with a projection in C. serrata ), and the slender scaphocerite (3.6-3.7 times as long as wide versus 3.0-3.2 times in C. serrata ). In addition, the four dark blue bands on the body of live shrimps allow an easy identification in the field. Caridina tetrazona sp. nov. also shows close similarity with C. cantonensis Yu, 1938 regarding the ratios of various segments of the 1st and 2nd pereiopods. Beside its peculiar coloration, C. tetrazona sp. nov. differs from C. cantonensis in the short rostrum, which only reaches the end of 1st segment of the antennular peduncle (versus distinctly reaches beyond the end of the 2nd segment in C. cantonensis ); the endopod of the male first pleopod slender (2.6-2.7 times as long as wide versus 2.1-2.4 times in C. cantonensis ) and distal part not dilated (versus distally distinctively dilated in C. cantonensis ); palp of 1st maxilliped ending in a finger-like tip (versus broadly rounded in C. cantonensis ); and absence of a projection on the posterior telsonic margin (versus with a projection in C. cantonensis ). Caridina tetrazona sp. nov. closely resembles C. trifasciata Yam & Cai, 2003, in having similar dark blue bands on their abdomen, and in having the shape of the endopod of the male 1st pleopod and appendix masculina of the male 2nd pleopod similar. Caridina tetrazona sp. nov. differs from C. trifasciata in its proportionately shorter rostrum (only reaches the end of the 1st segment of the antennular peduncle versus reaches beyond the end of the 2nd segment in C. trifasciata ); palp of the 1st maxilliped ending in a finger-like tip (versus broadly rounded in C. trifasciata ); and the slender scaphocerite (3.6-3.7 times as long as wide versus 2.8 times in C. trifasciata ).

Ecological notes.

The type specimens were collected from a small stream at an elevation of 8 m, stn 1, near Longtangzui, Dawanshan Island, Zhuhai City, Guangdong, China (21°56'59.2"N, 113°43'00"E) (Fig. 1 ). The stream is 2-3 m in width and 0.3-0.5 m in depth. The stream bed consists of rocks interspersed with gravel and sands patches. The bank was covered with aquatic vegetation. The shrimps live among rocks and marginal vegetation. The stream water was fast flowing and the temperature was 26 °C, pH was 6.4, and dissolved oxygen concentrations was 7.8 mg/1.

Distribution.

only known from Guangdong Province, southern China.

Figures

Figure 1. The light blue point shows the location of Dawanshan Island. The inset shows the sample locations. The yellow icon (stn 1) shows the collection site of Caridina tetrazona sp. nov., and red icons (stns 2 - 5) are the collection sites of C. serrata.

Figure 2. Habitats of the two shrimp species in this study. A Habitat of Caridina tetrazona sp. nov. B, C habitat of C. serrata.

Figure 3. Photos of live specimens of the two species of Caridina from Dawanshan Island. A Caridina tetrazona sp. nov. B dorsal view of C. serrata C lateral view of C. serrata.

Figure 4. Caridina tetrazona sp. nov. A Entire animal, lateral view, holotype (FU, 2017 - 06 - 27 - 01) B-I paratype (FU, 2017 - 06 - 27 - 02) B carapace and cephalic appendages, lateral view C antennule D antenna E mandible F maxillula G maxilla H first maxilliped I second maxilliped.

Figure 5. Caridina tetrazona sp. nov. paratype (FU, 2017 - 06 - 27 - 02). A Third maxilliped B first pereiopod C second pereiopod D third pereiopod E fifth pereiopod F first pleopod G second pleopod H telson I diaeresis of uropodal exopod.