Caridina wilsoni, Klotz & von Rintelen & von Rintelen, 2024

Caridina wilsoni n. sp.

Caridina sp. Gulf 1 Page, von Rintelen and Hughes, 2007;

Caridina sp. ‘Gulf 1’ Wilson, 2008;

Caridina sp. Gulf 1 Cook, Page and Hughes, 2011;

Caridina ‘sp. Gulf1’ Short, Page and Humphrey, 2019;

( Figures 5 View Figure 5 and 6 View Figure 6 ).

3.7. Material Examined

Holotype.:_ ♂ cl 3.4 mm, Australia, Queensland, Archer River catchment, Archer River at telegraph line , FNARH5/216, leg. DERM, 10.04.2000, QM W29816 .

Paratypes: One ov. ♀ cl 4.3 mm, same data as holotype, QM W29817 ; ♂ cl 3.0 mm, Australia, Queensland, Wenlock River catchment, Wenlock River at Stones Xing , leg. DERM, 10.04.2000, QM W29818 ; one ♀ cl 3.4 mm, commercial production ponds (most likely Blackmore R., could be Darwin R.), Darwin Area , cultured specimens provided by D. Wilson NTM Cr019572 ; seven ov. ♀♀ cl 3.2–4.0 mm, three ♂♂ cl 2.4–2.5 mm, Australia, Northern Territory, Top End, Darvin River crossing; S 12 ° 49.089 ′, E 130 ° 57.634 ′, 83-04, coll. N. Brinkmann and T. von Rintelen 27.6.2004, ZMB 29180 GoogleMaps ; two ♂♂ cl 1.9 and 2.2 mm, four ♀♀ cl 2.3–2.7 mm, Australia, Northern Territory, Top End, Coomalie Creek , S 13 ° 0.884 ′, E 131 ° 7.371 ′; coll. N. Brinkmann and T. von Rintelen 28.06.2003, ZMB 29240 GoogleMaps .

3.8. Comparative Material Examined

Syntypes. Caridina gracilirostris De Man, 1892 . Two ov. ♀♀ cl 5.2 and 5.3 mm, Indonesia, Celebes (=Sulawesi): river near Balangnipa 1888–1889, leg. M. Weber: RMNH.CRUS.D.2557 ; one ov. ♀ cl 5.3 mm, two ♂♂ cl 4.0 and 4.5 mm, Indonesia, Celebes (=Sulawesi), river near Balangnipa 1888–1889, leg. M. Weber, RMNH.CRUS.D.1076 .

Other material. Caridina gracillima Lanchester, 1901 . Two ♀♀ cl 5.2 and 5.3 mm, Malaysia, Peninsula, Terengganu, Kg. Dawi, Lake Kenyir , 05 ° 08.232 ′ N, 102 ° 48.211 ′ E (loc 56-10); leg. B. Stelbrink, 02. 06. 2010, ZMB 29578 GoogleMaps .

Three specimens, Malaysia, Sabah, Kinabatangan River at Sukau , N 5 ° 31 ′ 37.67 ′′ E 118 ° 17 ′ 39.23 ′′, leg. M. de Bruyn 01.01.2009 GoogleMaps ; two specimens ZMB 29579 . Thailand, Phitsanulok, Tributary of Kaek River, c. 28 km E of Phitsanulok , N 16 ° 50.866 ′ E 100 ° 30.709 ′, leg. F. Köhler 27.03.2006, ZMB 29513 GoogleMaps .

3.9. Description

Cephalothorax and cephalic appendages: Small shrimp with carapace lengths of 1.9–4.3 mm (median 2.8 mm, n = 22) in apparently adult specimens. Carapace ( Figure 5 A, B View Figure 5 ) smooth, antennal spine clearly separated from the suborbital lobe, pterygostomial angle broadly rounded. Rostrum ( Figure 5 A, B View Figure 5 ) long, reaching well beyond distal margin of scaphocerite, 1.04–2.31 (median 1.97, n = 8) times as long as carapace, curved upward; dorsal margin armed with 7–9 widely spaced teeth on proximal part of the rostrum, no teeth or occasionally with one tooth behind orbital margin, one subapical tooth near tip, ventral margin with 35 teeth. Rostrum formula based on 18 specimens 0 – 1 + 6 – 9 + 1/19 − 35. Eyes ( Figure 5 A, B View Figure 5 ) well developed with pigmented globular cornea. Antennular peduncle ( Figure 5 A, B, G View Figure 5 ), 0.86–1.02 (median 0.91, n = 7) times as long as carapace in females, 0.89–1.08 (median 1.00, n = 6) times as long as carapace in males, first segment 1.85–2.33 (median 2.16, n = 12) times as long as second segment, second segment 1.61–2.75 (median 2.05, n = 12) times longer than third segment; distolateral tooth on first segment acute, well developed, 0.23–0.39 (median 0.33, n = 11) times as long as second segment; second and third segments unarmed, with few spiniform setae near distal margin. Stylocerite acuminate, reaching to 0.70–1.04 (median 0.77, n = 11) times the length of basal segment of antennular peduncle. Antennal scaphocerite ( Figure 5 H View Figure 5 ) with well-developed distolateral tooth, 3.87–4.95 (median 4.66, n = 5) times as long as wide.

Pleon, telson and uropods: Sixth pleomere was 0.86–1.02 (median 0.92, n = 17) times the length of carapace, 1.81–2.41 (median 2.18, n = 17) times as long as the fifth pleomere, 1.08–1.30 (median 1.13, n = 15) times as long as telson. Telson ( Figure 5 C, D View Figure 5 ) slightly tapering distally, distal margin broadly convex, lacking a median point with three or four (n = 10) pairs of dorsal short spiniform setae and one pair of short spiniform setae dorsolaterally; distal margin with two pairs of spiniform setae, lateral pair stronger and longer compared to inner setae. Preanal carina ( Figure 5 E View Figure 5 ) with a prominent hook-like tooth. Uropodal diaeresis ( Figure 5 F View Figure 5 ) with 5–9 movable spiniform setae, outermost seta clearly shorter than lateral angle.

Mouthparts and branchiae: Shown in Figure 5I –N View Figure 5 and Figure 6A View Figure 6 . Similar to Caridina darwin n. sp. except that palp of first maxilliped ( Figure 5 L, M View Figure 5 ) terminates in a short blunt extension. Third maxilliped ( Figure 6 A View Figure 6 ) with last segment shorter than penultimate segment. Branchial apparatus as shown in Table 4 View Table 4 .

Pereiopods: Chela of first pereiopod ( Figure 6 B View Figure 6 ) was caridinoid in shape, with well-developed palm, 1.75–2.32 (median 2.10, n = 9) times as long as wide, 1.16–1.54 (median 1.41, n = 9) times as long as carpus; fingertips rounded, with prominent hooks hidden by tufts of setae ( Figure 6 C View Figure 6 ); dactylus 3.00–3.80 (median 3.29, n = 7) times as long as wide, 0.80–1.36 (median 1.13, n = 9) times as long as palm. Carpus slender, hardly excavated distally, 1.73–2.27 (median 2.00, n = 9) times as long as wide, 0.65–1.27 (median 1.14, n = 9) times as long as merus. Merus not inflated, 2.33–4.58 (median 2.48, n = 9) times as long as wide, 0.96–1.96 (median 1.06, n = 8) times as long as ischium. Chela of second pereiopod ( Figure 6 D View Figure 6 ) slender, caridinoid in shape, with well-developed palm, 2.21–2.75 (median 2.47, n = 9) times as long as wide, 0.80–0.94 (median 0.88, n = 9) times as long as carpus; fingertips rounded, with prominent hooks hidden by tufts of setae, dactylus 3.80–4.44 (median 4.17, n = 7) times as long as wide, 1.25–1.73 (median 1.33, n = 9) times as long as palm. Carpus slender, 3.73–4.94 (median 4.31, n = 9) times as long as wide, 1.17–1.41 (median 1.32, n = 9) times as long as merus. Merus not inflated, 3.50–5.00 (median 4.40, n = 9) times as long as wide, 0.91–1.06 (median 0.97, n = 8) times as long as ischium. Third pereiopod ( Figure 6 E – F View Figure 6 ) slender, dactylus ( Figure 6 F View Figure 6 ) not sexually dimorphic, 2.71–3.75 (median 3.75, n = 3) times as long as wide (including terminal claw and spiniform setae on flexor margin), terminating in one claw, with 6–8 accessory spiniform setae on flexor margin; propodus not dilated or curved distally, distal spiniform seta not enlarged, 7.88–10.60 (median 10.00, n = 3) times as long as wide, 3.00–3.53 (median 3.32, n = 3) times as long as dactylus; carpus 5.38–6.67 (median 5.65, n = 4) times as long as wide, 0.62–0.64 (n = 2) times as long as propodus, 0.50–0.56 (median 0.52, n = 4) times as long as merus, with one large spiniform seta near distal margin and one small spiniform setae proximal; merus 8.56–9.67 (median 8.85, n = 4) times as long as wide, 1.79–2.00 (median 1.93, n =4) times as long as carpus, with two or three strong movable spiniform setae on externo-inferior margin; ischium with one spiniform seta (absent in one specimen examined). Fourth pereiopod similar to third one but slightly smaller. Fifth pereiopod ( Figure 6 G, H View Figure 6 ) slender; dactylus ( Figure 6 H View Figure 6 ) 3.00–3.80 (median 3.63, n = 6) times as long as wide (including terminal claw and spiniform setae on flexor margin), terminating in one large claw, with 21–35 spiniform setae on flexor margin; propodus with small spiniform setae on ventral margin, distal pair of spiniform setae not markedly enlarged, propodus 10.75–12.14 (median 11.54, n = 5) times as long as wide, 3.07–3.54 (median 3.33, n = 5) times as long as dactylus; carpus 5.17–5.75 (median 5.43, n = 3) times as long as wide, 0.51–0.55 (median 0.53, n = 4) times as long as propodus, 0.53–0.61 (median 0.56, n = 4) times as long as merus, with one strong spiniform seta near distal margin; merus 8.33–10.73 (median 9.57, n = 3) times as long as wide, 1.63–1.90 (median 1.79, n = 4) times as long as carpus, with two or three strong, appressed, movable spiniform setae on the externo-inferior margin. Ischium without spiniform setae.

Pleopods: Endopod of male first pleopod ( Figure 6 I View Figure 6 ) elongated triangular, lacking appendix interna, 2.00—2.57 (median 2.45, n = 4) times as long as proximal width, 0.23–0.26 (median 0.24, n = 3) times as long as exopod, with long pappose setae on distal, inner and outer margins. Male second pleopod with appendix masculina rod-shaped ( Figure 6 J View Figure 6 ), 9.33–11.50 (n = 2) times as long as wide, 0.68–0.72 (n = 2) times as long as endopod, armed with strong spiniform setae on inner and distal margins; appendix interna originating from about 0.4 times the length of appendix masculina, reaching to 0.74–0.81 (n = 2) times the length of appendix masculina.

Reproductive biology: Ovigerous females with medium-sized embryos (0.59 − 0.66 × 0.34 − 0.43 mm (n = 8)). A total of 25–108 embryos counted in four ovigerous specimens.

Size. Postorbital carapace length of apparently adult specimens 1.9–4.3 mm.

Colouration: Body transparent. Rostrum red, red chromatophores also arranged in a narrow line running along the sternites of the pleon, on the distal part of the exopod of the uropod and a red transverse line at the dorsal margin of the third pleomere. Embryos are greenish (Wilson 2008; Short, Page and Humphrey 2019).

Distribution: The species is known from rivers flowing into the Gulf of Carpentaria (Queensland) and to the Timor Sea near Darwin (Northern Territory).

Etymology: The species is named after the biologist and aquarist Dave Wilson, collector of some of the type material and an enthusiast on Australian fish and shrimp fauna.

Common name: Darwin Red Nose Shrimp.

Remarks: Caridina wilsoni n. sp. Resembles Caridina gracilirostris De Man, 1892 , both in coloration and in general morphology (body very slender; rostrum strongly curved upwards with few widely spaced teeth on proximal part of dorsal margin, no postorbital teeth; preanal carina with one hook-like tooth; distal margin of telson with few spiniform setae). The proposed new species differs from this species in the larger size of the embryos (0.59–0.66 × 0.34–0.43 mm vs. 0.34–0.39 × 0.21–0.25 mm in C. gracilirostris ), a slightly stouter carpus of the second cheliped (3.73–4.94 times as long as wide vs. 4.69–5.26 times as long as wide in C. gracilirostris ), merus of third pereiopod 8.56–9.67 times as long as wide vs. 9.55–10.22 in C. gracilirostris , propodus of fifth pereiopod 3.07–3.54 times as long as dactylus vs. 4.0– 4.25 in C. gracilirostris . Some of these morphological characters overlap slightly (length-to-width ratio of carpus of second cheliped, length-to-width ratio of merus of third pereiopod), but by combining the morphological characters, these two species can be distinguished. The proposed new species also resembles C. gracillima Lanchester, 1901 , known from the Malayan peninsula, especially in the size of the embryos (0.59 –0.66 × 0.34–0.43 mm vs. 0.55– 0.66 × 0.35–0.40 mm in C. gracillima ) [ 26], but differs from this species in its preanal carina, bearing a hook-like spine vs. preanal carina rounded without a spine in C. gracillima .