Caridina schenkeli, Rintelen & Cai, 2009

Rintelen, Kristina von & Cai, Yixiong, 2009, Radiation Of Endemic Species Flocks In Ancient Lakes: Systematic Revision Of The Freshwater Shrimp Caridina H. Milne Edwards, 1837 (Crustacea: Decapoda: Atyidae) From The Ancient Lakes Of Sulawesi, Indonesia, With The Description Of Eight New Species, Raffles Bulletin of Zoology 57 (2), pp. 343-452 : 442-446

Caridina schenkeli , new species

( Figs. 60–62 ; Table 24)

Caridina spec. B – von Rintelen et al., 2007a: 1035, fig. 2, Tables 1-2.

Material examined. – Holotype: female (cl 4.3 mm)( MZB Cru 2124), small stream, west of Lake Poso , 02°2.613'S, 120°37.311'E, loc. 179-05, on macrophytes, coll. K. von Rintelen, 6 Oct.2005.

Paratypes ( Lake Poso catchment) – 38 ex. ( MZB Cru 1724, n=19; ZMB 29159, n=19), Uebangke River, north of tributary of Lake Poso, 01°46.48'S, 120°35.61'E, loc. 188-05, on mixed substrate, coll. K. von Rintelen, 7 Oct.2005 ; 24 ex. ( MZB Cru 1725, n=12; ZMB 29254, n=12), Sulewana, above rapids, 01°39.121'S, 120°39.742'E, loc. 52-04, on mixed substrate, coll. M. Glaubrecht & T. von Rintelen , 28 Mar.2004 ; 22 ex. ( MZB Cru 1726, n=11; ZMB 29407, n=11), Njongi River, approx. 1 km east of Tentena, 01°44.348'S, 120°40.102'E, loc. 163-05, on macrophytes, coll. K . & T. von Rintelen , 3 Oct.2005 ; 10 ex. ( ZMB 29441), small stream, west of Lake Poso , 01°53.816'S, 120°31.466'E, loc. 183-05, on roots, coll. K. von Rintelen, 6 Oct.2005 ; 43 ex. ( MZB Cru 1727, n=22; ZMB 29442, n=21 and few juveniles, some SEM material), small stream, west of Lake Poso, 02°2.613'S, 120°37.311'E, loc. 179-05, on macrophytes, coll. K. von Rintelen, 6 Oct.2005 ; 11 ex. ( MZB Cru 1728, n=5; ZMB 29443, n=6), stream, west of Lake Poso, 02°0.233'S, 120°35.765'E, loc. 180-05, mixed substrate, coll. K. von Rintelen, 6 Oct.2005 ; 25 ex. ( MZB Cru 1729, n=12; ZMB 29444, n=13), Salopa River, 01°46.333'S, 120°32.49'E, loc. 177-05 ,

Distribution. – Endemic to Lake Poso (excluding rivers), widely distributed within the lake ( Fig. 58 ), although less abundant than C. ensifera .

Biology and ecology. – C. sarasinorum was found on various kinds of substrate (wood, leaf litter, macrophytes), particularly on weed and wood, often in large numbers at several localities.

Colour pattern. – Body transparently yellowish or greenish, lacking a particular pattern. However, further details are still unknown.

Taxonomic remarks. – C. sarasinorum resembles C. longidigita , but can easily be distinguished by its stouter pereiopods and the short fingers on the chela of the first and second pereiopod (vs. distinctly more slender pereiopods and very long fingers in C. longidigita ). It further differs by a lower number of ventral rostral teeth (8-14, median 13 vs. 13-23, median 16 in C. longidigita ).

In the molecular phylogeny (Figs. 63,65), C. sarasinorum does not appear monophyletic, but based on its distinctive morphology it is here regarded as a single valid species that might sometimes hybridize with other species (compare von Rintelen et al., 2007a).

cl (mm) 3.6-5.1 4.2 ± 0.4 4.2 17 rl / cl 0.9-1.1 1.0 ± 0.1 0.9 10 n dorsal rostral teeth 9-16 13 ± 2 13 10 n ventral rostral teeth 9-13 11 ± 1 11 10 abds6 / cl 0.6-0.7 0.7 ± 0.0 0.7 17 abds6 / abds5 1.9-2.0 2.0 ± 0.1 2.0 6 abds6 / h tel 0.8-1.0 1.0 ± 0.1 1.0 8 h tel / w tel 3.0-3.6 3.4 ± 0.3 3.6 5 n spines uropodal diaeresis 10-11 10 ± 0 10 5 h ch1 / w ch1 1.9-3.2 2.4 ± 0.4 2.3 10 h ch1 / h ca1 1.1-1.4 1.3 ± 0.1 1.3 10 h ca1 / w ca1 2.1-3.2 2.5 ± 0.4 2.4 10 h ch2 / w ch2 2.5-4.4 3.3 ± 0.5 3.3 10 h ch2 / h ca2 0.7-0.9 0.8 ± 0.0 0.8 10 h ca2 / w ca2 4.5-6.5 5.5 ± 0.6 5.5 10 n spines p3 6-8 7 ± 1 7 5 n spines p5 57-64 59 ± 3 57 5

on mixed substrate, coll. K. & T. von Rintelen, 5 Oct.2005; 28 ex. ( MZB Cru 1730, n=14; ZMB 29445, n=14, some SEM material) , Sulewana , above rapids, 01°39.121'S, 120°39.742'E, loc. 169-05, on mixed substrate, coll. K. & T. von Rintelen, 4 Oct.2005; 34 ex. ( MZB Cru 1731, n=17; ZMB 29446, n=17) , Poso outlet, Tentena, 01°45.908'S, 120°38.366'E, loc. 195-05, on wood, coll. R. Lamers & K. von Rintelen, 7 Oct.2005; 4 ex. ( ZMB 29457) , Sulewana rapids, 02°38.871'S, 120°39.279'E, loc. 170-05, on macrophytes, coll. K. & T. von Rintelen, 4 Oct.2005 .

Description. – Carapace length 3.6-5.1 mm (n=17). Rostrum ( Fig. 61A ; Table 24) reaching near or beyond end of scaphocerite, 0.9-1.1 times as long as carapace (n=10), armed dorsally with 9-16 teeth (including 2-5 teeth posterior to orbital margin), approx. anterior third to half unarmed, without subapical teeth, armed ventrally with 9-13 teeth. Antennal spine situated below inferior orbital angle. Pterygostomial angle broadly rounded. Eyes well developed, anterior end 0.4-0.6 times length of basal segment of antennular peduncle (n=5). Antennular peduncle 0.8-1.0 times as long as carapace (n=5), second segment 1.6-2.0 times length of third segment, third segment 0.3-0.4 times length of basal segment. Stylocerite reaching 1.0 times length of basal segment of antennular peduncle (n=5). Scaphocerite ( Fig. 61D ) 3.3-4.7 times as long as wide (n=5).

Sixth abdominal somite 0.6-0.7 times length of carapace (n=17), 1.9-2.0 times as long as fifth somite (n=6), 0.8-1.0 times length of telson (n=8). Telson ( Fig. 61C,H ) 3.0-3.6 times as long as wide (n=5), distal margin rounded, without projection, with 3-6 pairs of spinules and 1 pair of dorsolateral spinules; distal end with 2-3 pairs of spines, lateral pair usually longer than intermediate pairs. Preanal carina ( Fig. 61E ) with a spine. Uropodal diaeresis ( Fig. 61B ) with 10-11 movable spinules (n=5).

5 pairs of pleurobranchs well developed; 3 pairs of arthrobranchs, 2 on third maxillipeds, with second pair strongly reduced in size, 1 pair on first pereiopod; 1 pair of podobranchs on second maxilliped reduced strongly to a laminate form. Epipod present on first two pereiopods. Incisor process of mandible ( Fig. 62A ) ending in a row of 4-6 small teeth, molar process truncated. Lower lacinia of maxillula ( Fig. 62B ) broadly rounded, upper lacinia elongate, with numerous distinct teeth and setae on inner margin, palp slender. Upper endites of maxilla ( Fig. 62C ) subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. Distal end of palp of first maxilliped ( Fig. 62F ) triangular, not ending with a finger-like projection; flagellum of the exopod short, endopod high, reaching near to end of flagellum of exopod. Second maxilliped ( Fig. 62E ) typical. Third maxilliped ( Fig. 62D ) with ultimate segment as long as penultimate segment.

Chela and carpus of first pereiopod distinctly stouter and broader than chela and carpus of second pereiopod ( Fig. 61 M-O); chela of first pereiopod 1.9-3.2 times as long as wide (n=10), 1.1-1.4 times length of carpus (n=10); tips of fingers rounded, without hooks; dactylus 1.0-1.4 times as long as palm (n=5); carpus 2.1-3.2 times as long as wide (n=10), 1.1-1.2 times length of merus (n=5). Chela of second pereiopod 2.5-4.4 times as long as wide (n=10), 0.7-0.9 times length of carpus (n=10); tips of fingers rounded, without hooks, dactylus 1.2-1.4 times as long as palm (n=5); carpus 4.5-6.5 times as long as wide (n=10), 1.3-1.4 times as long as merus (n=5).

Dactylus of third pereiopod ( Fig. 61F,I ) 3.3-4.3 times as long as wide (terminal spine included, without spines of flexor margin; n=5), terminating in one large claw with 6-8 accessory spines on flexor margin; propodus 9.8-14.2 times as long as wide, 3.4-4.8 times as long as dactylus; carpus 5.0-6.0 times as long as wide, 0.5-0.7 times as long as propodus, 0.5 times as long as merus; merus 8.5-10.5 times as long as wide, bearing 3-4 strong, movable spines on posterior margin of outer surface.

Dactylus of fifth pereiopod ( Fig. 61G,J ) 3.7-4.8 times as long as wide (terminal spine included, without spines of flexor margin; n=5), terminating in one large claw with 57- 64 accessory spines on flexor margin; propodus 11.5-17.0 times as long as wide, 2.8-4.5 times as long as dactylus; carpus 4.5-7.0 times as long as wide, 0.5 times as long as propodus, 0.6-0.7 times as long as merus; merus 7.2-9.3 times as long as wide, bearing 2-3 strong, movable spines on posterior margin of outer surface.

Endopod of male first pleopod ( Fig. 61K ) elongated triangular, 2.0-2.4 times as long as proximally wide (n=5), without appendix interna. Appendix interna of male second pleopod ( Fig. 56L ) 0.7-0.8 times length of appendix masculina (n=5).

Ovigerous females with 26- 37 eggs (n= 2 females); egg size 1.0-1.1 x 0.6-0.7 mm (n=30, eggs with and without eyes). Distribution. – C. schenkeli is endemic to the Poso catchment, but does not occur in the lake itself ( Fig. 60 ). So far, this species has not been found in rivers east and south of Lake Poso.

Biology and ecology. – C. schenkeli is an exclusively riverine species collected from various kinds of substrate (rocks, riverine vegetation, roots, dead wood). It was not found in sympatry with the other riverine species endemic to the Poso system ( C. acutirostris ).

Colour pattern. – Without any species specific pattern. Body colouration transparently yellowish or brownish, typical for many other riverine species from all over Sulawesi. Large (often ovigerous) females usually appear darker than smaller specimens.

Taxonomic remarks. – With regard to rostrum shape and body size, C. schenkeli resembles C. acutirostris (carapace length in mm 3.6-5.1, median 4.2 and 3.1-5.8, median 4.1 in C. acutirostris ), but differs by the ratio of rostrum to carapace length (0.9-1.1, median 0.9 vs. 0.3-0.7, median 0.5 in C. acutirostris ), a generally longer rostrum (reaching near or beyond end of scaphocerite vs. shorter in C. acutirostris ), and a higher number of ventral rostral teeth (9-13, median 11 vs. 4-9, median 4 in C. acutirostris ).

C. schenkeli is morphologically more variable than all other Poso species. In the molecular phylogeny (Figs. 63,65), C. schenkeli does not appear monophyletic, but based on its distinctive morphology it is here regarded as a single valid species that might sometimes hybridize with other species (compare von Rintelen et al., 2007a).

Figures

Fig. 60. Distribution of Caridina schenkeli in the Poso catchment.

Fig. 61. Caridina schenkeli from the Poso catchment. A. Cephalothorax and cephalic appendages, female (ZMB 29442); B. Uropodal diaeresis; C. Telson; D. Scaphocerite; E. Preanal carina, F. Third pereiopod; G. Fifth pereiopod; H. Distal end of telson; I. Dactylus of third pereiopod; J. Dactylus of fifth pereiopod; K. Endopod of male first pleopod (ZMB 29442); L. Appendix masculina of male second pleopod; M. First pereiopod, female (ZMB 29442); N. Second pereiopod; O. SEM image of chela and carpus of first and second pereiopods. Scale bars: A, D = 1.0 mm; C, E-G, K-O = 0.5 mm; B, H-J = 0.1 mm.

Fig. 62. Caridina schenkeli from the Poso catchment. A. Mandible (ZMB 29442); B. Maxillula; C. Maxilla; D. third maxilliped; E. second maxilliped; F. first maxilliped. Scale bars: A-F = 1mm.

Fig. 58. Distribution of Caridina sarasinorum in Lake Poso.

Fig. 56. Caridina longidigita from Lake Poso. A. Distribution. B. Colour pattern of living animal (not to scale). Picture courtesy of Chris Lukhaup.