Caridina acutirostris Schenkel, 1902

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 : 424-428

Caridina acutirostris Schenkel, 1902

( Figs. 48–50 ; Table 18)

Caridina acutirostris Schenkel, 1902: 496 , pl. 8, Figs. 3 a-c, 4b (type locality: area south of Lake Poso, approx. 600 m above sealevel).

Caridina acutirostris – Roux, 1904: 551; Bouvier, 1905: 73, 1925: 166, Figs. 353-355; Chace, 1997: 6; Cai & Wowor, 2007: 314; von Rintelen et al., 2007a: 1033, fig. 2; Tables 1-2, 2008: 2244, Table 1.

Sixth abdominal somite 0.6 times length of carapace (n=9), 1.7-2.0 times as long as fifth somite (n=5), 0.9-1.0 times length of telson (n=5). Telson ( Fig. 49G,J ) 3.0-3.3 times as long as wide (n=5), distal margin rounded, without projection, with 4-5 pairs of spinules and 1 pair of dorsolateral spinules; distal end with 4-5 pairs of spines. Preanal carina ( Fig. 49E ) with a spine. Uropodal diaeresis ( Fig. 49F ) with 11-17 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 present on first two pereiopod, reduced or totally absent from third pereiopod. Incisor process of mandible ( Fig. 50A ) ending in a row of 3- 5 small teeth, molar process truncated. Lower lacinia of maxillula ( Fig. 50B ) broadly rounded, upper lacinia elongate, with numerous distinct teeth and setae on inner margin, palp slender. Upper endites of maxilla ( Fig. 50C ) subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. Distal end of palp of first maxilliped ( Fig. 50F ) triangular, ending with a short finger-like projection; flagellum of the exopod elongated, endopod high, not exceeding the flagellum of

Material examined. – Holotype: female (cl 5.2mm) ( NHMB 3 a), area south of Lake Poso , approx. 600 m above sealevel, coll. Sarasin, 1907.

Lake Poso catchment: 14 ex. ( MZB Cru 1843, n=7; ZMB 29439, n=7), Tonusu, approx. 3 km south of Tonusu towards Siuri, 01°48.95'S, 120°31.18'E, loc. 185-05, on macrophytes, coll. K. von Rintelen, 6 Oct.2005 ; 11 ex. ( MZB Cru 1844, n=5; ZMB 29440, n=6 and some juveniles, some SEM material), stream south of Pendolo , 02°8.702'S, 120°43.854'E, loc. 196-05, on roots, coll. K. von Rintelen, 8 Oct.2005 .

Description. – Carapace length 3.1-5.8 mm (n=11). Rostrum ( Fig. 49 A-C; Table 18) short, usually shorter than scaphocerite, reaching to or near distal end of second segment of antennular peduncle, in large females sometimes reaching near end of scaphocerite, 0.3-0.7 times as long as carapace (n=11), armed dorsally with 10-13 teeth (including 3-4 teeth posterior to orbital margin), about anterior third to half unarmed, without subapical teeth, armed ventrally with 4-9 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 0.7-1.1 times as long as carapace (n=5), second segment 1.4-1.8 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. 49D ) 3.0-3.6 times as long as wide (n=5).

cl (mm) 3.1-5.8 4.3 ± 0.7 4.1 11 rl / cl 0.3-0.7 0.5 ± 0.1 0.5 11 n dorsal rostral teeth 10-13 11 ± 1 11 11 n ventral rostral teeth 4-9 5 ± 2 4 11 abds6 / cl 0.6 - - 9 abds6 / abds5 1.7-2.0 1.8 ± 0.1 1.8 5 abds6 / h tel 0.9-1.0 1.0 ± 0.0 1.0 5 h tel / w tel 3.0-3.3 3.1 ± 0.1 3.1 5 n spines uropodal diaeresis 11-17 14 ± 2 13 5 h ch1 / w ch1 2.0-2.6 2.3 ± 0.2 2.2 8 h ch1 / h ca1 1.2-1.3 1.3 ± 0.0 1.3 8 h ca1 / w ca1 2.0-2.7 2.2 ± 0.3 2.1 8 h ch2 / w ch2 2.9-3.4 3.2 ± 0.2 3.2 8 h ch2 / h ca2 0.8-0.9 0.8 ± 0.0 0.8 8 h ca2 / w ca2 4.5-5.9 5.1 ± 0.5 4.9 8 n spines p3 4-9 6 ± 2 6 5 n spines p5 45-66 55 ± 7.6 55 5

exopod in length. Second maxilliped ( Fig. 50D ) typical. Third maxilliped ( Fig. 50E ) with ultimate segment slightly shorter than penultimate segment.

Chela and carpus of first pereiopod distinctly stouter and broader than chela and carpus of second pereiopod ( Fig. 49 O-Q); chela of first pereiopod 2.0-2.6 times as long as wide (n=8), 1.2-1.3 times length of carpus (n=8); tips of fingers rounded, without hooks; dactylus 0.7-1.4 times as long as palm (n=5); carpus 2.0-2.7 times as long as wide (n=8), 1.1-1.2 times length of merus (n=5). Chela of second pereiopod 2.9-3.4 times as long as wide (n=8), 0.8-0.9 times length of carpus (n=8); tips of fingers rounded, without hooks, dactylus 1.0-1.4 times as long as palm (n=5); carpus 4.5-5.9 times as long as wide (n=8), 1.4-1.6 times as long as merus (n=5).

Dactylus of third pereiopod ( Fig. 49H,K ) 3.2-3.9 times as long as wide (terminal spine included, without spines of flexor margin; n=5), terminating in one large claw with 4-9 accessory spines on flexor margin; propodus 8.6-11.1 times as long as wide, 3.3-3.7 times as long as dactylus; carpus 4.6-5.7 times as long as wide, 0.6-0.7 times as long as propodus, 0.5 times as long as merus; merus 7.1-9.2 times as long as wide, bearing 2-3 strong, movable spines on posterior margin of outer surface. Dactylus of fifth pereiopod ( Fig. 49I,L ) 4.0-5.6 times as long as wide (terminal spine included, without spines of flexor margin; n=5), terminating in one large claw with 45-66 accessory spines on flexor margin; propodus 10.0-12.5 times as long as wide, 2.9-3.2 times as long as dactylus; carpus 4.1-5.5 times as long as wide, 0.5 times as long as propodus, 0.6 times as long as merus; merus 6.7-7.9 times as long as wide, bearing 2-3 strong, movable spines on posterior margin of outer surface.

Endopod of male first pleopod ( Fig. 49M ) elongated triangular, 2.1-2.4 times as long as proximally wide (n=4), without appendix interna. Appendix interna of male second pleopod ( Fig. 49N ) 0.7-0.8 times length of appendix masculina (n=4).

Ovigerous females with 23- 54 eggs (n= 2 females); egg size 1.1-1.3 x 0.7-0.8 mm (n=20, eggs with and without eyes).

Distribution. – C. acutirostris is endemic to the Poso river catchment occurring in streams around the lake ( Fig. 48 ). So far only known from two distant localities, the southern one is the type locality “Salukuwa and other small streams, drainage of Kodina River, south of Lake Poso”, where Fritz and Paul Sarasin collected the specimens of C. acutirostris (Sarasin & Sarasin, 1905: 238) later described by Schenkel (1902).

In the molecular phylogeny (Figs. 63,65), two specimens referred to as C. cf. acutirostris from the Tomori region cluster with specimens of C. acutirostris (compare von Rintelen et al., 2007a). These have not been included here due to differences in morphology and their geographic origin. Their taxonomic status awaits further investigation.

Biology and ecology. – C. acutirostris is an exclusively riverine species that was collected from vegetation (green parts and roots). It was never found in sympatry with the other riverine species endemic to the Poso system ( C. schenkeli ).

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

Taxonomic remarks. – C. acutirostris differs from all Poso species by the short rostrum (usually not reaching end of scaphocerite vs. longer in all other species) and the ratio of rostrum to carapace length (0.3-0.7, median 0.5 vs. over 0.7 in the other species). With regard to the rostrum and body size, C. acutirostris mainly resembles C. schenkeli (carapace length in mm 3.1-5.8, median 4.1 and 3.6-5.1, median 4.2 in C. schenkeli ), but differs by the length of the rostrum (shorter in C. acutirostris ), and a lower number of ventral rostral teeth (4-9, median 4 vs. 9-13, median 11 in C. schenkeli ). Further, C. acutirostris can resemble specimens of C. mahalona (Malili lakes) with a short rostrum, although the scaphocerite usually is stouter (3.0-3.6 times as long as wide vs. 3.5-4.1 times as long as wide in C. mahalona ). Further, the carpus of the first and second pereiopod is stouter (2.0-2.7 and 4.5-5.9 times as long as wide vs. 2.5- 3.3 and 5.6-7.0 times as long as wide in C. mahalona ). The general range of parameters (for example the number of rostral teeth) is usually higher in C. mahalona than in C. acutirostris (Tables 10,19).

In the molecular phylogeny ( Figs. 63 , 65 ) C. acutirostris is genetically distinct from all other Poso species, however appears within the Poso clade (for a detailed discussion see von Rintelen et al., 2007a).

Figures

Fig. 48. Distribution of Caridina acutirostris in the Poso catchment.

Fig. 49. Caridina acutirostris from the Lake Poso catchment. A. Schenkel’s drawing of cephalothorax and cephalic appendages (modified from 1902); B. Cephalothorax and cephalic appendages, male (ZMB 29440); C. Cephalothorax and cephalic appendages, another male (ZMB 29440); D. Scaphocerite, female (ZMB 29440); E. Preanal carina, F. Uropodal diaeresis, male (ZMB 29440); G. Telson; H. Third pereiopod; I. Fifth pereiopod; J. Distal end of telson; K. Dactylus of third pereiopod; L. Dactylus of fifth pereiopod; M. Endopod of male first pleopod; N. Appendix masculina of male second pleopod; O. First pereiopod; P. Second pereiopod; Q. SEM image of chela and carpus of first and second pereiopods. Scale bars: B-D = 1.0 mm; E,G-I, M-Q = 0.5 mm; F, J-L = 0.1 mm; A = no scale available.

Fig. 50. Caridina acutirostris from the Lake Poso catchment. A. Mandible (ZMB 29440); B. Maxillula; C. Maxilla; D. second maxilliped; E. third maxilliped; F. first maxilliped. Scale bars: A-F = 1mm.

Fig. 3. Standard morphometric characters in Caridina. A. Cephalothorax and abdomen (shrimp drawing modified from Woltereck, 1937a: 215). B. Rostrum and cephalic appendages. C. First and second pereiopod. D. Tailfan (telson and uropods). E. Third and fifth pereiopod. Abbreviations. antp (length of antennular peduncle), cl (carapace length), rl (rostrum length), abds5 (length of fifth abdominal somite), abds6 (length of sixth abdominal somite), h tel (length/height of telson), w tel (width of telson), h ch1 (length/height of chela of first pereiopod), w ch1 (width of chela of first pereiopod), h ca1 (length/height of carpus of first pereiopod), w ca1 (width of carpus of first pereiopod), h ch2 (length/height of chela of second pereiopod), w ch2 (width of chela of second pereiopod), h ca2 (length/height of carpus of second pereiopod), w ca2 (width of carpus of second pereiopod), n spines p3 (number of spines on the dactylus of the third pereiopod), n spines p5 (number of spines on the dactylus of the fifth pereiopod).

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. 65. Bayesian Inference phylogram (mtDNA, 16S and COI) showing taxa within the Poso clade (tree topology from von Rintelen et al., in review). For each sequenced specimen museum accession numbers are provided. Locality abbreviations (compare Fig. 1): PS (Lake Poso), PSca (Lake Poso catchment).