Caridina nana, Mazancourt & Boseto & Marquet & Keith, 2020

Mazancourt, Valentin de, Boseto, David, Marquet, Gerard & Keith, Philippe, 2020, Solomon’s Gold Mine: Description or redescription of 24 species of Caridina (Crustacea: Decapoda: Atyidae) freshwater shrimps from the Solomon Islands, including 11 new species, European Journal of Taxonomy 696, pp. 1-86 : 59-62

Caridina nana sp. nov.

urn:lsid:zoobank.org:act:312659E0-1F36-4BAB-9714-2FBC71B57C6A

Figs 2P , 19

Caridina cf. weberi sp. 6 – de Mazancourt et al. 2019a: 166 , 169–170.

Etymology

This species is named after its small size.

Material examined

Holotype

SOLOMON ISLANDS • ♀, cl 3.0mm; Vella Lavella Island , Maravari River; 07°51.703´S, 156°41.748´E; 31 Oct. 2016; P. Keith and C. Lord leg.; DNA voucher: CA1903; MNHN-IU- 2018-2912.

Paratype

SOLOMON ISLANDS • 1 ♀, cl 2.7 mm; same collection data as for holotype; DNA voucher: CA1902; MNHN-IU- 2018-2913 .

Comparative material

Caridina parvirostris De Man, 1892

INDONESIA • 2 syntypes, ♂♂, cl 3.1–3.2 mm; Flores Island , river near Bombang; Jan. 1889; M. Weber leg.; MHNN-IU-2015-1748 • 1 syntype, ♀, cl 4.2 mm; same collection data as for preceding; MNHN- IU-2015-1754 .

Description

CEPHALOTHORAX. Suborbital angle indistinguishably fused with antennal spine. Pterygostomian margin rounded. Rostrum ( Fig. 19k ): bent down, very short, 0.2–0.3 of cl, not reaching to first segment of antennular peduncle, armed with 7 teeth on dorsal margin, 0 of them situated on carapace behind orbital margin, ventral margin with 1 tooth. Eyes well developed, anterior end reaching to 0.72 length of basal segment of antennular peduncle. Short antennular peduncle 0.36–0.49 times as long as carapace. Anterolateral angle reaching 0.37 length of second segment, second segment longer than third segment. Stylocerite reaching to 0.95 length of basal segment of antennular peduncle.

PEREIOPODS. Epipods on first four pereiopods. P1 ( Fig. 19 a–b): chela about 1.9–2.0 times as long as wide, movable finger 2.5–2.8 times as long as wide, 0.7–0.9 times length of palm; carpus 1.6–1.7 times as long as wide. P2 ( Fig. 19c ) more slender and longer than first pereiopod, with chela 2.8–2.9 times as long as wide: movable finger 5.1 times as long as wide, 1.6–1.8 times length of palm; carpus slender, 6.6–6.8 times as long as wide. P3 ( Fig. 19d ): stout, dactylus ( Fig. 19f ) 2.7–3.0 times as long as wide (terminal one spiniform seta included), with 4–5 spiniform setae on flexor margin in addition to terminal; propodus 8.1–9.6 times as long as wide, 4.0–4.8 times as long as dactylus. P5 ( Fig. 19e ): dactylus ( Fig. 19g ) 3.2–3.4 times as long as wide, with 26–28 spiniform setae on flexor margin; propodus 11.5–13.6 times as long as wide, 4.2–4.7 times as long as dactylus.

ABDOMEN. Third abdominal somite with moderately convex dorsal profile. Sixth abdominal somite 0.47 times as long as carapace, 1.5 times as long as fifth somite, 0.91 times as long as telson.

TELSON ( Fig. 19i ). slender, 4.3 times as long as wide, with four pairs of dorsal spinules and pair of dorsolateral spinules; posterior margin with median process, rounded, with 6–7 very long intermediate setae longer than lateral ones.

MALE PLEOPODS. No males.

PRE- ANAL CARINA ( Fig. 19j ). High, unarmed.

UROPODAL DIAERESIS ( Fig. 19h ). With 16–17 spinules.

EGGS. Size: 0.39–0.41 × 0.19–0.21.

Habitat

This species is largely rheophile and prefers fresh and well-oxygenated waters from the higher course of rivers.

Colour pattern

Unknown.

Distribution

As far as we know, this new species occurs only in Vella Lavella ( Solomon Islands).

Remarks

These specimens from the Solomon Islands are very similar to C. parvirostris by the long P2 carpus, 6.6–6.8 times as long as wide (vs 6.0– 7.4 in C. parvirostris ), but are different by the bent rostrum with fewer and smaller dorsal teeth 6–7 (vs 8–10), by the shorter P1 dactylus, 2.5–2.8 times as long as wide (vs 3.0–3.4), and also the shorter P1 chela, 1.9–2.0 times as long as wide (vs 2.0–2.3).

Figures

Fig. 2. Bayesian inference phylogenetic tree of the species studied. Numbers above branches are Bayesian posterior probabilities, numbers under branches are Maximum Likelihood bootstrap values. Results of the three species delimitation methods are indicated by the black bars on the right of the tree. Each bar represents a species recognized by the analysis.

Fig. 19. Caridina nana sp. nov. a. First pereiopod. b. Details of the fingers of the first pereiopod. c. Second pereiopod. d. Third pereiopod. e. Fifth pereiopod. f. Dactylus of third pereiopod. g. Dactylus of fifth pereiopod. h. Uropodal diaeresis. i. Telson. j. Pre-anal carina. k. Cephalothorax. MNHN- IU-2018-2912 (a–k).