Caridina longidigita Cai & Wowor, 2007

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 : 436-439

Caridina longidigita Cai & Wowor, 2007

( Figs. 56–57 ; Table 22)

Caridina longidigita Cai & Wowor, 2007: 317 , Figs. 4-5 (type locality: west coast of Lake Poso at Taipa area, Poso River at the outlet of Lake Poso, east coast of Lake Poso at Besuna village).

Caridina longidigita – von Rintelen et al., 2008: 2244, Table 1.

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

Material examined. – Lake Poso: 42 ex. ( MZB Cru 1704a, n=5; ZMB 29060a, n=6; MZB Cru 1705b, n=9; ZMB 29060b, n=12; MZB Cru 1706c, n=5; ZMB 29060c, n=5, some SEM material), east shore, south of Cape Sinampada, 02°56.25'S, 120°40.443'E, loc. 159-04, (a) on rocks in deeper water, (b) on wood, (c) on rocks in shallow water, coll. K . & T. von Rintelen , 16 Aug.2004 ; 14 ex. ( MZB Cru 1707, n=7; ZMB 29252, n=7, some SEM material), east shore, south of Cape Tolambu, 01°57.928'S, 120°40.536'E, loc. 65-04, on rocks, coll. M. Glaubrecht & T. von Rintelen , 30 Mar.2004 ; 4 ex. ( ZMB 29258), west shore, Cape Bancea , 01°59.023'S, 120°35.108'E, loc. 59-04, on rocks, coll. M. Glaubrecht & T. von Rintelen , 29 Mar.2004 ; 7 ex. ( ZMB 29289), east shore, 02°0.825'S, 120°42.007'E, loc. 161-04, on wood, coll. K. von Rintelen, 16 Aug.2004; ( ZMB 29293, some juveniles) , east shore, 01°59.867'S, 120°41.238'E, loc. 160-04, on mixed substrate, coll. K. & T. von Rintelen , 16 Aug.2004 ; 1 ex. ( ZMB 29387), west shore, 02°2.734'S, 120°37.368'E, loc. 178-05, on wood, coll. K. von Rintelen, 6 Oct.2005 ; 22 ex. ( MZB Cru 1708, n=11; ZMB 29390, n=11, some SEM material), east shore, bay at Cape Nceppo, 01°52.39'S, 120°38.974'E, loc. 156-05, on mixed substrate, coll. K. von Rintelen, 3 Oct.2005 ; 8 ex. ( ZMB 29391), east shore, at road Tentena-Peura , 01°47.33'S, 120°38.079'E, loc. 160-05, on wood, coll. K. von Rintelen, 3 Oct.2005 ; 5 ex. ( ZMB 29398), east shore, shallow bay at Cape Songuo , 01°53.748'S, 120°39.939'E, loc. 155-05, on mixed substrate, coll . R. Lamers & K. von Rintelen, 3 Oct.2005 ; 3 ex. ( ZMB 29401), west shore, Taipa , 01°55.289'S, 120°32.77'E, loc. 182-05, on wood, coll. K. von Rintelen, 6 Oct.2005 ; 1 ex. ( ZMB 29456), west shore, 01°58.21'S, 120°34.316'E, loc. 181-05, on wood, coll. K. von Rintelen, 6 Oct.2005 .

Description. – Carapace length 2.9-4.1 mm (n=12). Rostrum ( Fig. 57A ; Table 22) long with an anterior upturn, mostly reaching beyond end of scaphocerite, 0.9-1.4 times as long as carapace (n=11), armed dorsally with 16-21 teeth (including 4-6 teeth posterior to orbital margin), approx. anterior third to half unarmed, without subapical teeth, armed ventrally with 13-23 teeth (n=8). Antennal spine situated below inferior orbital angle. Pterygostomial angle broadly rounded. Eyes well developed, anterior end 0.5-0.6 times length of basal segment of antennular peduncle (n=5). Antennular peduncle 1.0-1.1 times as long as carapace (n=5), second segment 1.5-0.2 times length of third segment, third segment 0.3-0.4 times length of basal segment. Stylocerite reaching 0.9-1.0 times length of basal segment of antennular peduncle (n=5). Scaphocerite ( Fig. 57D ) 3.8-4.3 times as long as wide (n=5).

Sixth abdominal somite 0.5-0.7 times length of carapace (n=11), 1.7-1.9 times as long as fifth somite (n=10), 1.0-1.1 times length of telson (n=6). Telson ( Fig. 57C,H ) 2.9-3.1 times as long as wide (n=5), distal margin broadly rounded, without projection, with 3-4 pairs of spinules and 1 pair of dorsolateral spinules; distal end with 4 pairs of spines, lateral pair longer than intermediate pairs, median pairs shortest. Preanal carina ( Fig. 57E ) with a spine. Uropodal diaeresis ( Fig. 57B ) with 15-17 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. Epipods absent from all pereiopods. Mouthparts as described by Cai & Wowor (2007).

Chela and carpus of first pereiopod not distinctly stouter and broader than chela and carpus of second pereiopod ( Fig. 57 K-N); chela of first pereiopod long and slender, 4.6-6.5 times as long as wide (n=9), 0.7-1.0 times length of carpus (n=10); tips of fingers rounded, without hooks, but with extremely long fingers (about length of or longer than chela); dactylus 3.6-4.6 times as long as palm (n=5); carpus 4.8-8.1 times as long as wide (n=8), 1.0-1.2 times length of merus (n=5). Chela of second pereiopod 4.8-6.4 times as long as wide (n=9), 0.7-1.0 times length of carpus (n=10); tips of fingers rounded, without hooks, but with extremely long fingers (about length of or longer than chela); dactylus 3.4-3.9 times as long as palm (n=5); carpus 5.2-7.9 times as long as wide (n=8), 1.0-1.3 times as long as merus (n=5).

Third pereiopod ( Fig. 57F,I ) slender, dactylus 3.1-3.6 times as long as wide (terminal spine included, without spines of flexor margin; n=5), terminating in one large claw with 4-5 accessory spines on flexor margin; propodus 11.5-15.0 times as long as wide, 4.7-6.5 times as long as dactylus; carpus 6.4-8.5 times as long as wide, 0.7-0.8 times as long as propodus, 0.5-0.6 times as long as merus; merus 9.4-11.5 times as long as wide, bearing 3-5 strong, movable spines on posterior margin of outer surface.

Fifth pereiopod slender ( Fig. 57G,J ), dactylus 2.9-3.9 times as long as wide (terminal spine included, without spines of flexor margin; n=5), terminating in one large claw with 26- 33 accessory spines on flexor margin; propodus 12.9-20.0 times as long as wide, 4.6-6.7 times as long as dactylus; carpus 6.3-7.5 times as long as wide, 0.6 times as long as propodus, 0.6 times as long as merus; merus 9.1-10.2 times as long as wide, bearing 2-4 strong, movable spines on posterior margin of outer surface.

Endopod of male first pleopod ( Fig. 57O ) elongated triangular, 1.9-2.3 times as long as proximally wide (n=5), without appendix interna. Appendix interna of male second pleopod ( Fig. 57P ) 0.8-0.9 times length of appendix masculina (n=5).

Ovigerous females with 24- 29 eggs (n= 2 females); egg size 1.0-1.2 x 0.6-0.7 mm (n=20, eggs with and without eyes).

Distribution. – Endemic to Lake Poso (excluding rivers) and widely distributed within the lake ( Fig. 56A ), although less abundant than C. ensifera .

Biology and ecology. – Cai & Wowor (2007) already mentioned the occurrence of C. longidigita on “rocky substrates”. This could not only be confirmed in the field, but also further differentiated in gravel from shallow water (above 3 m) and boulders in deeper water (below 3 m). Additional samples from wood show this species to be a typical hard-substrate dweller. Further, C. longidigita shows a unique feeding behaviour that has not been reported from any species of Caridina so far. Instead of the common feeding behaviour described by Fryer (1960), C. longidigita makes lateral sweeping movements with its extremely long fingers cl (mm) 2.9-4.1 3.5 ± 0.3 3.4 12 rl / cl 0.9-1.4 1.2 ± 0.2 1.3 11 n dorsal rostral teeth 16-21 18 ± 2 18 8 n ventral rostral teeth 13-23 16 ± 4 16 8 abds6 / cl 0.5-0.7 0.6 ± 0.1 0.6 11 abds6 / abds5 1.7-1.9 1.8 ± 0.1 1.7 10 abds6 / h tel 1.0-1.1 1.0 ± 0.0 1.0 6 h tel / w tel 2.9-3.1 3.0 ± 0.1 3.0 5 n spines uropodal diaeresis 15-17 16 ± 1 16 5 h ch1 / w ch1 4.6-6.5 5.6 ± 0.5 5.6 9 h ch1 / h ca1 0.7-1.0 0.9 ± 0.1 0.9 10 h ca1 / w ca1 4.8-8.1 6.6 ± 1.1 6.7 8 h ch2 / w ch2 4.8-6.4 5.5 ± 0.5 5.5 9 h ch2 / h ca2 0.7-1.0 0.9 ± 0.1 0.8 10 h ca2 / w ca2 5.2-7.9 6.7 ± 1.1 7.1 8 n spines p3 4-5 5 ± 1 5 5 n spines p5 26-33 30 ± 3 30 5

(M. Glaubrecht & T. von Rintelen, pers. field observation 2007), while all other species lack this lateral component.

Colour pattern. – Body appearing transparently brownish to greenish (sometimes darker), with small dots covering the whole body. Fingers of chelae orange, but without a particular pattern ( Fig. 56B ). Eggs dark brown.

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

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

Figures

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

Fig. 57. Caridina longidigita from Lake Poso. A. Cephalothorax and cephalic appendages, male (ZMB 29252); B. Uropodal diaeresis; C. Telson; D. Scaphocerite, male (ZMB 29390); E. Preanal carina, F. Third pereiopod, male (ZMB 29252); G. Fifth pereiopod; H. Distal end of telson; I. Dactylus of third pereiopod; J. Dactylus of fifth pereiopod; K. First pereiopod, female (ZMB 29390); L. Second pereiopod; M. SEM image of anterior part of chelae (from top: lateral, ventral, setae), male (ZMB 29252); N. SEM image of chela and carpus of first and second pereiopods, male (ZMB 29390); O. Endopod of male first pleopod; P. Appendix masculina of male second pleopod. Scale bars: A, D = 1.0 mm; E-G, K-P = 0.5 mm; B, H-J = 0.1 mm.

Fig. 4. Caridina dennerli from the Malili lake system. A. Distribution. B.-C. Colour pattern of living animals (not to scale). Pictures courtesy of Chris Lukhaup.

Fig. 5. Caridina dennerli from the Malili lake system. A. Cephalothorax and cephalic appendages, female (ZMB 29049); B. Uropodal diaeresis, male (ZMB 29051); C. Telson, male (ZMB 29156); D. Scaphocerite, male (ZMB 29051); E. Preanal carina, F. Third pereiopod, female (ZMB 29326); G. Fifth pereiopod; H. Distal end of telson male (ZMB 29156); I. Dactylus of third pereiopod female (ZMB 29326); J. Dactylus of fifth pereiopod; K. Endopod of male first pleopod (ZMB 29051); L. Appendix masculina of male second pleopod; M. First pereiopod, male (ZMB 29156); N. Second pereiopod; O. SEM image of anterior part of chela, male (ZMB 29104); P. SEM image of chela and carpus of first and second pereiopods, female (ZMB 29024). Scale bars: A, D = 1.0 mm; C, E-G, K-P = 0.5 mm; B, H-J = 0.1 mm.