Caridina mahalona Cai, Wowor & Choy, 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 : 381-387

Caridina mahalona Cai, Wowor & Choy, 2009

( Figs. 20–23 ; Table 9)

Caridina mahalona Cai et al., 2009: 29 , Figs. 8-9 (type locality: Lake Mahalona at southwest coast).

Material examined. – Lake Mahalona catchment: 1 ex. ( ZMB 29466, some SEM material), Ponsoa River, 02°32.243'S, 121°31.818'E, loc. F1-02, substrate unknown, coll. F. Herder, 7 Nov.2002 .

Lake Matano catchment – 44 ex. ( MZB Cru 1835, n=22; ZMB 29069, n=22, some SEM material), Lawa River , near mouth at northwest shore of Lake Matano, 02°25.75'S, 121°13.27'E, loc. 25-03, on leaf litter, coll. K . & T. von Rintelen , 13 Sep.2003 ; 20 ex. ( MZB Cru 1836, n=10; ZMB 29096, n=10), river, near mouth at northwest corner of Lake Matano , 02°25.88'S, 121°13.08'E, loc. 24-03, on mixed substrate, coll. K . & T. von Rintelen , 13 Sep.2003 ; 5 ex. ( ZMB 29295, some SEM material), small stream northwest of Lake Matano , 02°25.846'S, 121°13.097'E, loc. 126-04, on macrophytes, coll . T. von Rintelen , 1 Aug.2004 .

Lake Towuti catchment – 19 ex. ( MZB Cru 1840, n=9; ZMB 29067, n=10, some SEM material), Lengkona River, 02°40.82'S, 121°41.77'E, loc. 86-03, on leaf litter, coll. K . & T. von Rintelen , 2 Oct.2003 ; 1 ex. ( ZMB 29192), Kondube River , at road north of Matompi, near Timampu, 02°38.36'S, 121°24.98'E, loc. 37-03, on roots, coll. K . & T. von Rintelen , 15 Sep.2003 ; 36 ex. ( MZB Cru 1841, n=18; ZMB 29210, n=18, some SEM material), Bombongan River, 02°52.38'S, 121°22.54'E, loc. 49-03, on leaf litter, coll. K . & T. von Rintelen , 20 Sep.2003 ; 17 ex. ( MZB Cru 1842, n=9; ZMB 29212, n=8), stream, tributary of Bombongan River, 02°51.59'S, 121°21.61'E, loc. 48-03, on leaf litter, coll. K . & T. von Rintelen , 20 Sep.2003 .

Patingko River (Malili lake system) – 35 ex. ( MZB Cru 1838, n= 17; ZMB 29085, n=18, some SEM material), at road Tabarano , off road Malili-Soroako north of Balambano, 02°38.222'S, 121°14.56'E, loc. 14-03, on mixed substrate, coll. K . & T. von Rintelen , 15 Sep.2003 ; 1 ex. ( ZMB 29184, n=1), Kondara River (tributary of Patingko River ), at road Malili-Soroako, east of Leduledu, 02°35.11'S, 121°17.34'E, loc. 36-03, on leaf litter, coll. K . & T. von Rintelen , 15 Sep.2003 ; 14 ex. ( MZB Cru 1839, n=7; ZMB 29196, n=7), south of road Malili-Soroako, 02°37.17'S, 121°14.95'E, loc. 33-03, on rocks, coll. K . & T. von Rintelen , 15 Sep.2003 ; 14 ex. ( ZMB 29197, some SEM material), at road Malili-Soroako , in Togo village, 02°36.53'S, 121°15.56'E, loc. 34-03, on leaf litter, coll. K . & T. von Rintelen , 15 Sep.2003 .

Tomori (north of the Malili lake system) – 10 ex. ( MZB Cru 1837, n=5; ZMB 29061, n=5, some SEM material), Momonsi River; at road Nuha-Beteleme, 02°25.36'S, 121°21.43'E, loc. 64-03, on leaf litter, coll. K. & T. von Rintelen, 25 Sep.2003 .

Description. – Carapace length 2.8-5.2 mm (n=17). Rostrum ( Fig. 21 A-E; Table 9) length variable, short to long, sometimes reaching slightly beyond end of scaphocerite, sometimes distinctly shorter, 0.5-1.0 times as long as carapace (n=21), armed dorsally with 7-21 teeth (including 1-6 teeth posterior to orbital margin), approx. anterior 1/4 to 2/3 unarmed, without subapical teeth armed ventrally with 2-9 teeth. Antennal spine situated below inferior orbital angle. Pterygostomial angle broadly rounded. Eyes well developed, anterior end 0.6-0.7 times length of basal segment of antennular peduncle (n=5). Antennular peduncle 0.7-0.9 times as long as carapace (n=5), second segment 1.5-1.8 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. 21F,K,P ) 3.5-4.1 times as long as wide (n=5).

Sixth abdominal somite 0.5-0.7 times length of carapace (n=17), 1.7-1.9 times as long as fifth somite (n=5), 0.9-1.0 times length of telson (n=17). Telson ( Fig. 21G,J,L,O,Q,T ) 2.9-3.3 times as long as wide (n=6), distal margin rounded, without projection, with 3-4 pairs of spinules and 1 pair of dorsolateral spinules; distal end with 3-4 pairs of spines, lateral pair distinctly stronger but not always longer than cl (mm) 2.8-5.2 4.5 ± 0.7 4.4 17 rl / cl 0.5-1.0 0.7 ± 0.2 0.7 21 n dorsal rostral teeth 7-21 13 ± 3 14 20 n ventral rostral teeth 2-9 5 ± 2 4 20 abds6 / cl 0.5-0.7 0.6 ± 0.0 0.6 17 abds6 / abds5 1.7-1.9 1.8 ± 0.1 1.8 5 abds6 / h tel 0.9-1.0 0.9 ± 0.1 0.9 17 h tel / w tel 2.9-3.3 3.2 ± 0.2 3.2 6 n spines uropodal diaeresis 12-15 13 ± 1 13 6 h ch1 / w ch1 2.0-2.5 2.3 ± 0.2 2.4 9 h ch1 / h ca1 0.7-1.4 1.2 ± 0.1 1.2 24 h ca1 / w ca1 2.5-3.3 2.9 ± 0.3 2.8 9 h ch2 / w ch2 2.6-3.4 2.9 ± 0.2 2.8 9 h ch2 / h ca2 0.7-1.3 0.8 ± 0.1 0.7 23 h ca2 / w ca2 5.6-7.0 6.3 ± 0.5 6.2 9 n spines p3 5-6 5 ± 1 5 6 n spines p5 39-57 51 ± 6 52 6

intermediate pairs. Preanal carina ( Fig. 21H,M,R ) with a spine. Uropodal diaeresis ( Fig. 21I,N,S ) with 12-15 movable spinules (n=6).

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 pereiopod. Incisor process of mandible ( Fig. 23A ) ending in a row of 4-5 small teeth, molar process truncated. Lower lacinia of maxillula ( Fig. 23B ) broadly rounded, upper lacinia elongate, with numerous distinct teeth and setae on inner margin, palp slender. Upper endites of maxilla ( Fig. 23C ) subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. Distal end of palp of first maxilliped ( Fig. 23D ) triangular, ending with a finger-like projection; flagellum of the exopod very elongated, endopod high, not exceeding the flagellum of exopod in length. Second maxilliped ( Fig. 23F ) typical. Third maxilliped ( Fig. 23E ) with ultimate segment distinctly shorter than penultimate segment.

Chela and carpus of first pereiopod distinctly stouter and broader than chela and carpus of second pereiopod ( Fig. 22 E-F,M-N,U-V); chela of first pereiopod 2.0-2.5 times as long as wide (n=9), 0.7-1.4 times length of carpus (n=24); tips of fingers rounded, without hooks; dactylus 1.1-1.4 times as long as palm (n=9); carpus 2.5-3.3 times as long as wide (n=9), 1.1-1.4 times length of merus (n=8). Chela of second pereiopod 2.6-3.4 times as long as wide (n=9), 0.7- 1.3 times length of carpus (n=23); tips of fingers rounded, without hooks, dactylus 1.1-1.5 times as long as palm (n=9); carpus 5.6-7.0 times as long as wide (n=9), 1.3-1.5 times as long as merus (n=8).

Third pereiopod ( Fig. 22 A-B,I-J,Q-R) slender, dactylus 3.0- 4.4 times as long as wide (terminal spine included, without spines of flexor margin; n=6), terminating in one large claw with 5-6 accessory spines on flexor margin; propodus 9.0- 13.0 times as long as wide, 3.6-4.5 times as long as dactylus; carpus 4.9-5.8 times as long as wide, 0.6-0.7 times as long as propodus, 0.5-0.6 times as long as merus; merus 7.1-10.0 times as long as wide, bearing 2-3 strong, movable spines on posterior margin of outer surface.

Fifth pereiopod slender ( Fig. 22 C-D,K-L,S-T), dactylus 3.9- 5.4 times as long as wide (terminal spine included, without spines of flexor margin; n=6), terminating in one large claw with 39-57 accessory spines on flexor margin; propodus 9.6- 14.9 times as long as wide, 2.8-3.7 times as long as dactylus; carpus 4.7-5.7 times as long as wide, 0.5-0.6 times as long as propodus, 0.6-0.7 times as long as merus; merus 6.1-8.5 times as long as wide, bearing 2-3 strong, movable spines on posterior margin of outer surface.

Endopod of male first pleopod ( Fig. 22G,O,W ) elongated triangular, 1.7-2.7 times as long as proximally wide (n=5), without appendix interna. Appendix interna of male second pleopod ( Fig. 22H,P,X ) 0.7-0.9 times length of appendix masculina (n=5).

Ovigerous females with 10- 24 eggs (n= 3 females); egg size 1.0-1-2 x 0.6-0.8 mm (n=28, eggs with and without eyes).

Distribution. – C. mahalona mainly occurs in rivers within the Malili lakes’ catchment ( Fig. 20 ), but was also found at one locality north of Lake Matano (Tomori area), outside of the system. Therefore, it is the only non-endemic species occurring in the Malili system.

Biology and ecology. – C. mahalona is an exclusively riverine species, dwelling on various kinds of substrate (leaf litter, riverine vegetation, roots, dead wood). Except for one riverine locality very close to Lake Matano (loc. 24-03), where it occurred together with C. holthuisi , C. mahalona was never found in sympatry with any other species (not even the other riverine species of the Malili lake system, C. masapi ).

Colour pattern. – Without any species specific pattern. Body colouration transparently yellowish or brownish, similar to C. masapi , C. acutirostris , C. schenkeli , and many other riverine species from all over Sulawesi. Large (often ovigerous) females usually appear darker than smaller specimens.

Taxonomic remarks. – C. mahalona mostly resembles C. masapi , but both species were never found together at any locality. C. mahalona is generally larger than C. masapi (carapace length 2.8-5.2, median 4.4 vs. 2.1-4.6, median 3.1 in C. masapi ), its rostrum displays a higher degree of variability than in C. masapi , and differs by the number of teeth on the dactylus of the fifth pereiopod (39-57, median 52 vs. 30-44, median 33 in C. masapi ). In specimens with a short rostrum, C. mahalona can resemble C. acutirostris from Lake Poso, although the scaphocerite usually is more slender (3.5-4.1 times as long as wide vs. 3.0-3.6 times as long as wide in C. acutirostris ); the same applies to the carpus of the first and second pereiopod (2.5-3.3 and 5.6-7.0 times as long as wide vs. 2.0-2.7 and 4.5-5.9 times as long as wide in C. acutirostris ). The general range of parameters (for example the number of rostral teeth) is usually higher in C. mahalona than in C. acutirostris (compare Tables 10,19).

In the molecular phylogeny ( Figs. 63-64 ), C. mahalona appears in three allopatric clades (drawings of representatives of each clade are shown in Figs. 21-22 ). The high degree of rostrum variability partly occurs within populations, and no significant morphological differences where found between members of the different clades. However, the geographic pattern might suggest the existence of cryptic species (compare von Rintelen et al., in review).

Figures

Fig. 20. Distribution of Caridina mahalona in the Malili lake system and the Tomori area.

Fig. 21. Caridina mahalona from the Malili lake system (each of the three columns shows a representative of a different genetic clade; compare remarks for details). Cephalothorax and cephalic appendages from: A. Male (ZMB 29069); B. Female (ZMB 29061); C. Female (ZMB 29085); D. Male (ZMB 29210); E. Female (ZMB 29067). F. Scaphocerite, female (ZMB 29061); G. Telson, male (ZMB 29069); H. Preanal carina, female (ZMB 29061); I. Uropodal diaeresis, male (ZMB 29069); J. Distal end of telson; K. Scaphocerite, male (ZMB 29210); L. Telson; M. Preanal carina; N. Uropodal diaeresis; O. Distal end of telson; P. Scaphocerite, female (ZMB 29085); Q. Telson, female (ZMB 29197); R. Preanal carina, female (ZMB 29085); S. Uropodal diaeresis, female (ZMB 29197); T. Distal end of telson, female (ZMB 29197). Scale bars: A-F, J, O = 1.0 mm; G-H, J, L-M, O, Q-R, T = 0.5 mm; I, N, S = 0.1 mm.

Fig. 22. Caridina mahalona from the Malili lake system (each of the three columns shows a representative of a different genetic clade; compare remarks for details). A. Third pereiopod, female (ZMB 29069); B. Dactylus of third pereiopod; C. Fifth pereiopod; D. Dactylus of fifth pereiopod; E. First pereiopod, female (ZMB 29295), F. Second pereiopod; G. Endopod of male first pleopod (ZMB 29061); H. Appendix masculina of male second pleopod; I. Third pereiopod, male (ZMB 29210); J. Dactylus of third pereiopod; K. Fifth pereiopod; L. Dactylus of fifth pereiopod; M. First pereiopod; N. Second pereiopod; O. Endopod of male first pleopod; P. Appendix masculina of male second pleopod; Q. Third pereiopod, female (ZMB 29197); R. Dactylus of third pereiopod; S. Fifth pereiopod; T. Dactylus of fifth pereiopod; U. First pereiopod; V. Second pereiopod; W. Endopod of male first pleopod (ZMB 29085); X. Appendix masculina of male second pleopod. Scale bars: A, C, E-I, K, M-Q, S, U-X = 0.5 mm; B, D, J, L, R, T = 0.1 mm.

Fig. 23. Caridina mahalona from the Malili lake system. A. Mandible (ZMB 29067); B. Maxillula; C. Maxilla; D. first maxilliped; E. third maxilliped; F. second maxilliped. Scale bars: A-F = 1mm.

Fig. 8. Caridina glaubrechti from the Malili lake system. A. Cephalothorax and cephalic appendages, female (ZMB 29053); B. Preanal carina, male (ZMB 29109); C. Uropodal diaeresis, female (ZMB 29053); D. Scaphocerite, male (ZMB 29109); E. Dactylus of third pereiopod, female (ZMB 29074), F. Telson, female (ZMB 29053); G. Telson, another female (ZMB 29053); H. Third pereiopod, female (ZMB 29074); I. Dactylus of fifth pereiopod; J. Fifth pereiopod; K. Endopod of male first pleopod (ZMB 29109); L. Appendix masculina of male second pleopod; M. Distal end of telson, female (ZMB 29053); N. Distal end of telson, another female (ZMB 29053); O. First pereiopod, female (ZMB 29053); P. Second pereiopod; Q. SEM image of chela and carpus of first and second pereiopods, female (ZMB 29053). Scale bars: A, D = 1.0 mm; B, F-H, J-L, O-Q = 0.5 mm; C, E, I, M-N = 0.1 mm.

Fig. 9. Caridina glaubrechti from the Malili lake system. A. Mandible (ZMB 29053); B. Maxillula; C. Maxilla; D. second maxilliped; E. third maxilliped; F. first maxilliped. Scale bars: A-F = 1mm.

Fig. 63. Bayesian Inference phylogram (mtDNA, 16S and COI) of Caridina from the ancient lakes of Sulawesi (for other taxa compare von Rintelen et al., in review). Numbers on branches are, from top, Bayesian posterior probabilities, ML and MP bootstrap values. The scale bar indicates the number of substitutions per site. For each sequenced specimen museum accession numbers are provided. Locality abbreviations (compare Fig. 1): Lam (Lampesue River catchment), LT (Lake Lontoa), MHL (Lake Mahalona), MS (Lake Masapi), MT (Lake Matano), MTca (Lake Matano catchment), Pat (Patingko River), Pon (Ponsoa River), TW (Lake Towuti), TWca (Lake Towuti catchment), PS (Lake Poso), PSca (Lake Poso catchment), SSul (South Sulawesi), SESul (Southeast Sulawesi).

Fig. 64. Bayesian Inference phylogram (mtDNA, 16S and COI) showing taxa within the two Malili clades (for other taxa compare von Rintelen et al., 2009). For each sequenced specimen museum accession numbers are provided. Locality abbreviations (compare Fig. 1): Lam (Lampesue River catchment), LT (Lake Lontoa), MHL (Lake Mahalona), MS (Lake Masapi), MT (Lake Matano), MTca (Lake Matano catchment), Pat (Patingko River), Pon (Ponsoa River), TW (Lake Towuti), TWca (Lake Towuti catchment), SSul (South Sulawesi).