Caridina fusca Klotz, Wowor & K. von Rintelen, 2021

Klotz, Werner, Rintelen, Thomas von, Wowor, Daisy, Lukhaup, Chris & Rintelen, Kristina von, 2021, Lake Poso's shrimp fauna revisited: the description of five new species of the genus Caridina (Crustacea, Decapoda, Atyidae) more than doubles the number of endemic lacustrine species, ZooKeys 1009, pp. 81-122 : 81

Caridina fusca Klotz, Wowor & K. von Rintelen sp. nov. Figures 3H , 5 , 6

Material examined.

Holotype: ov. ♀ cl. 2.9 mm (MZB Cru 5031), Indonesia, Central Sulawesi, Lake Poso, E shore, S of Tentena, dive at small cape, 15 m, 1°46.39'S, 120°38.33'E, M. Glaubrecht and T. von Rintelen leg., 12 May 2007. Paratypes: 1 ov. ♀ cl. 2.7 mm, 1 ♂ cl. 2.3 mm (MZB Cru 5032), 2 ♀♀ cl. 2.9 and 3.1 mm (ZMB 29518), same data as holotype; 1 ov. ♀ cl. 2.8 mm (MZB Cru 5033), Lake Poso, E shore, S of Tentena, dive at small cape, 15 m, 1°46.394'S, 120°38.327'E, coll. J. Pfaender and T. von Rintelen leg., 21 Sep. 2015; 1 ♀ cl. 2.4 mm (ZMB 29622), Lake Poso, E shore, S of Tentena, dive at small cape, 10 m, 1°46.394'S, 120°38.327'E, coll. J. Pfaender and T. von Rintelen leg., 21 Sep. 2015; 1 ov. ♀ cl. 2.7 mm (MZB Cru 5034), 1 ♀ cl. 2.5 mm (ZMB 30223), Lake Poso, E shore, S of Tentena, dive at small cape, 15 m, 1°46.394'S, 120°38.327'E, coll. T. von Rintelen and W. Klotz leg., 12 May 2017; 1 ov. ♀ cl. 2.9 mm (ZMB 30715), Lake Poso, W shore, Bay S of cape, in ca. 6 m depth, 1°55.408'S, 120°33.315'E, coll. T. von Rintelen leg., 4 Jul. 2018. 1 ov. ♀ cl. 2.4 mm (MZB Cru 5090), Lake Poso, E shore, small bay within mouth of outlet, 1°46.30'S, 120°38.38'E, T. von Rintelen leg., 14 Jul 2019.

Description.

Cephalothorax and cephalic appendages. Postorbital carapace length 2.4-2.8 mm (n = 10). Rostrum (Fig. 5A-C ) moderately long, straight or slightly sigmoid, reaching to end of antennular peduncle, dorsal and ventral margin armed throughout almost to tip, 0.78-0.94 (median 0.87, n = 7) times as long as carapace, rostral formula 5-7 + 12-17 / 7-9. Antennal spine fused with or slightly separated from orbital margin. Pterygostomial angle broadly rounded. Eyes well developed with globular cornea. Antennular peduncle (Fig. 5A, C, H ), 0.84-0.90 (median 0.86, n = 4) times as long as carapace, first segment 1.71-2.14 (median 1.81, n = 4) times as long as second segment, second segment 2.33-3.00 (median 2.83, n = 4) times longer than third segment. Tooth on distolateral margin of first segment of antennular peduncle acute. Stylocerite reaching to 0.85-0.89 (median 0.87, n = 4) of first segment of antennular peduncle. Scaphocerite (Fig. 5I ) 3.81-4.00 (median 3.90, n = 2) times as long as wide, inner and distal margin beset with plumose setae.

Abdominal somites, telson, and uropods. Sixth abdominal somite 0.54-0.58 (median 0.56, n = 4) times carapace length, 1.53-2.21 (median 1.77, n = 4) times as long as fifth somite, 0.94-1.00 (median 0.98, n = 4) times as long as telson. Distal margin of telson (Fig. 5F, G ) convex without a median projection, with three pairs of short spiniform setae dorsally and one pair of short spiniform setae dorsolaterally; distal end with six long spiniform setae, lateral pair longer than others. Preanal carina (Fig. 5D ) with a hook-like spine. Uropodal diaeresis (Fig. 5E ) with 11-13 short movable spiniform setae, outermost ones shorter than lateral angle.

Mouthparts and branchiae. Incisor process of mandible (Fig. 5J ) ending in irregular teeth, molar process truncated. Lower lacinia of maxillula (Fig. 5K ) broadly rounded, upper lacinia elongate, with numerous distinct teeth on inner margin, palp slender with few pappose setae and one conical spiniform seta near tip. Upper endites of maxilla (Fig. 5L ) subdivided, palp slender, scaphognathite tapering posteriorly, fringed with long, curved setae at posterior margin. Palp of first maxilliped (Fig. 5M, N ) ending in a slender triangular extension. Podobranch on second maxilliped (Fig. 5O ) reduced to a lamina. Third maxilliped (Fig. 5P ) with one well developed and one small arthrobranch, ultimate segment of maxilliped shorter than penultimate segment. First pereiopod with a small arthrobranch. Pleurobranchs present on all pereiopods. Epipod slightly reduced (without distal hook) on third maxilliped, absent from all pereiopods.

Pereiopods . Chelae of first and second pereiopods (Fig. 6A, B ) well developed; chela of first pereiopod 2.29-2.73 (median 2.33, n = 7) times as long as wide, 1.17-1.34 (median 1.31, n = 7) times length of carpus; tips of fingers rounded, without hooks, with tufts of hairs near tip; dactylus 0.94-1.21 (median 1.11, n = 7) times as long as palm; carpus slender, hardly excavated distally, 2.33-3.00 (median 2.58, n = 7) times as long as wide, 1.21-1.32 (median 1.29, n = 5) times length of merus. Merus 2.32-3.43 (median 2.83, n = 5) times as long as wide, 0.85-0.96 (median 0.86, n = 4) times as long as ischium. Chela of second pereiopod 2.70-3.94 (median 3.31, n = 4) times as long as wide, 0.62-0.87 (median 0.74, n = 7) times length of carpus; tips of fingers rounded, without hooks, with tufts of hairs near tip; dactylus 1.11-1.50 (median 1.21, n = 7) times as long as palm; carpus 4.89-7.17 (median 6.14, n = 7) times as long as wide, 1.33-1.51 (median 1.46, n = 7) times as long as merus; merus 4.00-6.40 (median 4.71, n = 7) times as long as wide, 0.82-1.06 (median 0.94, n = 4) times as long as ischium. Third pereiopod (Fig. 6C, D ) not sexually dimorphic, dactylus 4.00-4.67 (median 4.13, n = 4) times as long as wide (terminal claw and spiniform setae on flexor margin included), terminating in one large claw with 3-6 stout spiniform setae on flexor margin; propodus slender, 8.40-12.00 (median 9.22, n = 4) times as long as wide, 2.63-3.24 (median 2.92, n = 4) times as long as dactylus; carpus bearing one strong and three or four small spiniform setae on posterior margin of outer surface, 4.63-5.13 (median 4.86, n = 3) times as long as wide, 0.73-0.81 (median 0.75, n = 4) times as long as propodus; merus slender, 5.84-6.70 (median 6.46, n = 3) times as long as wide, 1.97-2.05 (median 1.97, n = 4) times as long as carpus, bearing 3-5 strong spiniform setae on posterior margin of outer surface. Ischium with one spiniform seta. Fifth pereiopod (Fig. 6E, F ) slender, dactylus 5.67 times as long as wide (terminal claw and serrate setae on flexor margin included), terminating in one large claw with 34-36 serrate setae on flexor margin; propodus slender, 10.89-15.43 (median 13.16, n = 2) times as long as wide, 3.18 times length of dactylus, carpus bearing one strong and three small spiniform setae on posterior margin of outer surface, 0.53 times as long as propodus; merus slender, 7.83 times as long as wide, 1.81 times length of carpus, bearing two strong spiniform setae on posterior margin of outer surface. Ischium without a strong spiniform seta.

Pleopods. Appendix masculina (Fig. 6G ) on male second pleopod stick-like, with long spiniform setae on inner and distal margin, few pappose setae on basal part, appendix interna reaching to ~ 0.8 of appendix masculina.

Colouration.

Body dark reddish or brown with tiny light bluish dots, well-defined white transversal bands on the first, third, fifth, and sixth abdominal segments (Fig. 3H ).

Reproductive biology and larval development.

Ovigerous females with few eggs (35, n = 1). Size of eggs 0.77-0.81 × 0.44-0.49 mm (n = 3).

Etymology.

The Latin word fuscus refers to the species’ dark reddish or brown colouration (Fig. 3H ).

Distribution.

Caridina fusca sp. nov. is endemic to Lake Poso. Specimens were found at two localities within the lake, in a small bay south of the town of Tentena at the east shore and in a bay at the west shore.

Ecology.

Caridina fusca sp. nov. is found under rocks in deep water (more than 5 m depth), while the morphologically similar species C. sarasinorum is usually found on various kinds of substrate like deposits of leaf litter, on wood or macrophytes ( von Rintelen and Cai 2009).

Remarks.

In life colouration, C. fusca sp. nov. might be confused with C. sarasinorum , also endemic to Lake Poso. In the latter, the transversal bands on the abdomen are less defined and scraggy compared to the sharply defined straight bands in C. fusca sp. nov. In preserved condition C. fusca sp. nov. can be differentiated from C. sarasinorum by the rostrum reaching to the end of the antennular peduncle, the dorsal and ventral margin armed throughout almost to the tip vs. reaching to the distal margin of the scaphocerite or beyond, unarmed in anterior one-third to half of the dorsal margin in C. sarasinorum . Epipods are reduced on the third maxilliped and absent on all pereiopods of C. fusca sp. nov. vs. well-developed on the third maxilliped and first pereiopod, absent on second to fifth pereiopods in C. sarasinorum . The chelae of the first pair of pereiopods are not inflated, 2.29-2.73 times as long as wide, 1.17-1.34 times as long as the carpus in C. fusca sp. nov. vs. slightly inflated, 1.74-2.10 times as long as wide, 1.35-1.48 times as long as the carpus in C. sarasinorum . The carpi of the first pair of pereiopods are more slender (2.33-4.00 times as long as wide) and hardly excavated distally vs. more stout (1.75-2.22 times as long as wide) and slightly excavated distally in C. sarasinorum .

Figures

Figure 3. Living specimens of Caridina spp in Lake Poso 2. A, B Caridina mayamareenae sp. nov. C C. lilianae sp. nov. D Two snail species Celetaia persculpta and Tylomelania sp. on soft substrate. Empty shells of these species are shelter for C. mayamareenae sp. nov. E, F C. poso sp. nov. G C. marlenae sp. nov. H C. fusca sp. nov. Not to scale. All photographs: W. Klotz.

Figure 5. Caridina fusca sp. nov. Morphology 1. Paratype ov. ♀, cl. 2.7 mm, MZB Cru 5034 A cephalothorax and cephalic appendages C rostrum D preanal carina E uropodal diaeresis F, G telson I scaphocerite J distal part of mandible K maxillula M first maxilliped N Palp of first maxilliped O second maxilliped P third maxilliped; paratype ov. ♀, cl. 2.7 mm, MZB Cru 5032 B rostrum H antennular peduncle L maxilla. Scale bars: 1 mm (A-C, F, H, I); 0.5 mm (D, E, G, J-M, O); 0.1 mm (N).

Figure 6. Caridina fusca sp. nov. Morphology 2. Paratype ov. ♀, cl. 2.7 mm, ZMB 30223 A first pereiopod B second pereiopod C third pereiopod D dactylus of third pereiopod; paratype ov. ♀, cl. 2.7 mm, ZMB 29518 E fifth pereiopod F dactylus of fifth pereiopod; paratype ♂, cl. 2.3 mm, MZB Cru 5032 G appendix masculina on male second pleopod. Scale bars: 1 mm (A-C, E); 0.5 mm (D, F, G).