Caridina thambipilaii Johnson, 1961

Cai, Yixiong, Ng, Peter K. L. & Choy, Satish, 2007, Freshwater Shrimps Of The Family Atyidae (Crustacea: Decapoda: Caridea) From Peninsular Malaysia And Singapore, Raffles Bulletin of Zoology 55 (2), pp. 277-309 : 289-294

Caridina thambipilaii Johnson, 1961

( Figs. 8–10 )

Caridina thambipillaii Johnson, 1961:138 , Figs.25–27 [type locality: Sungai Putat near the pumping station, Malacca, Peninsular Malaysia]; Johnson, 1965: 8; Ng & Choy, 1990:16; Wowor et al., 2004: 343, Fig. 7P–S .

Material examined. – Holotype: male, cl 3.9 mm, ZRC 1979.4 .18.41, Sungai Putat near the pumping station, Malacca, Peninsular Malaysia, coll. D. J. Johnson, 6 Jan.1956.

Allotype: 1 ovigerous female, cl 6.5 mm, eggs 0.30 × 0.25mm, ZRC 1979.4 .18.42, data same as holotype.

Paratypes: 2 males, cl 3.6–4.1 mm, ZRC 1979.4.18 –19, data same as holotype .

Others: Peninsular Malaysia: 2 females, cl 3.2–3.3 mm, ZRC 2007.0388 , Malaysia, Johor Mawai , Tg. Sedili Road, Sungai Selangi, 22 Apr.1992 ; 5 males, cl 3.6–3.9 mm, 9 females, cl 4.1–5.6 mm, ZRC 2007.0389 , about 112 km, market on Johor Bahru to Kuantan road, north of K. Rompin, Pahang, Malaysia, 19 Oct.1991 ; 1 male, cl 3.6 mm, 1 ovigerous female, cl 6.0 mm, ZRC.1979.4.18.51–52, Malaysia: Johor, Kota Tinggi, Mawai road, tidal stream above mangrove limit, among weeds, 18 Jul.1961 .

Comparative material examined. – Borneo: 2 males, cl 3.2–3.3 mm, 1 female, cl 4.9 mm, 1 ovigerous female, cl 4.8 mm, ZRC 2007.0390 , 8.6 km after turning towards Sungai Cina, Matang, 1°39'2.6"N 110°10'44.7"E, after entrance to Matang Reserve , Sarawak, Malaysia, coll. H. H. Tan, 4 Sep.1995 ; 3 females, cl 5.1–5.9 mm, 1 ovigerous female, cl 5.7 mm, eggs 0.47 × 0.30 mm, ZRC 2007.0391 , Sungai Stunggang, 4.8 km before Lundu ferry point at Bg. Kayan, Sarawak, Malaysia, coll. H. H Tan, 2 Sep.1996; 1 ovigerous female, cl 5.9 mm, ZRC 2007.0392 , Borneo: Sarawak, Bau-Lundu area , Sungai Stunggang , swamp forest, 51.0 km towards Lundu from Bau on Bau-Lundu road, 01°37.44'N 109°53.18'E, pH 4.6, coll. H. H. Tan & P. Yap, 2 Oct.1998. Myanmar : 3 males, cl 3.1–3.5 mm, ZRC 1979.4.17.78–80, brackish pond near railway crossing N. Okkalatia Rd. , Rangoon (Yangon), coll. C. H. Fernando, no date .

Description.− Rostrum ( Figs. 8A , 9A , 10A ) short, straight or slightly crested basally, reaching near middle of second segment of antennular peduncle; rostral formula 3–4+11– 17/1–4. Suborbital angle acute, fused with antennal spines; pterygostomian margin rounded.

Sixth abdominal somite 0.5 times of carapace, 1.6 times as long as fifth somite, as long as telson. Telson ( Figs. 8B, C ) 3.7 times as long as wide, distal margin broadly rounded, not terminating in a projection, with 4 or 5 pairs of dorsal spinules and a pair of dorsolateral spinules; distal end with 4 pair of spines, lateral pair longer than intermediate pairs. Preanal carina without spine.

Eyes well developed, anterior end reaching to 0.7 times length of basal segment of antennular peduncle. Antennular peduncle 0.7 times as long as carapace; basal segment of antennular peduncle subequal to combined length of second and third segments, anterolateral angle reaching to 0.3 times length of second segment, second segment distinctly longer than third segment. Stylocerite reaching to 0.8 times length of basal segment of antennular peduncle. Scaphocerite 3.3 times as long as wide.

Incisor process of mandible ( Fig. 8D ) ending in irregular teeth, molar process truncated. Lower lacinia of maxillula ( Fig. 8E ) broadly rounded, subrectangular, upper lacinia elongated, with a number of distinct teeth on inner margin, palp slender. Endites much small, upper endites of maxilla ( Fig. 8F ) subdivided, palp short, scaphognathite very broad, tapering posteriorly with numerous long, curved setae at posterior end. Palp of first maxilliped ( Fig. 8G ) ending in a prominent finger-like projection. Second maxilliped ( Fig. 8H ) with a large developed arthrobranch. Third maxilliped reaching to end of antennular peduncle, with ultimate segment shorter than penultimate segment ( Fig. 8I ).

Epipods well developed on first 3 pereiopods, reduced or absent on fourth pereiopod. First pereiopod ( Figs. 9B , 10B ) reaching beyond end of basal segment of antennular peduncle; merus 2.9–3.0 times as long as broad, shorter than carpus; carpus excavated anteriorly, shorter than chela, 3.3–3.6 times as long as high; chela 3.2–3.6 times as long as broad; fingers 1.2–1.3 times as long as palm. Second pereiopod ( Figs. 9C , 10C ) reaching to end of scaphocerite; merus shorter than carpus, 5.1–5.7 times as long as broad; carpus 1.4 times as long as chela, 8.0–8.6 times as long as high; chela 5.1–5.3 times as long as broad; fingers 1.4–1.6 times as long as palm. Third pereiopod ( Figs. 9D, E , 10D, E ) reaching to end of scaphocerite, sexually dimorphic, that of male with propodus 13 times as long as broad, 4.9 times as long as dactylus; dactylus broad, 2.2 times as long as wide (spines included), terminating in 2 claws, with 5 accessory large spines on flexor margin; that of female with propodus 12 times as long as broad, 4.4 times as long as dactylus, dactylus slender, 3.3 times as long as wide (spinules included), terminating in 2 claws, with 6 spinules on flexor margin. Fifth pereiopod ( Figs. 10G, H ) reaching to end of second segment of antennular peduncle, propodus 16 times as long as broad, 3.0 times as long as dactylus; dactylus slender, 5.0 times as long as wide (spinules included), terminating in a claw, with 70–106 spinules on flexor margin.

Endopod ( Fig. 10F ) of male first pleopod subrectangular, 1.9 times as long as wide, reaching to 1/3 length of endopod, no appendix interna.Appendix masculina of male second pleopod ( Fig. 10G ) stout, reaching to 3/4 length of exopod.

Uropodal diaeresis ( Fig. 8K ) with 16–19 movable spinules.

Ovigerous females with egg size 0.40–0.47 × 0.25–0.30 mm.

Habitat. − Streams.

Remarks. – With respect to the slender pereiopods, the form of the pleopods, and the sexual dimorphism of the third and fourth pereiopods, C. thambipilaii most closely resembles C. laevis Heller, 1862 from Java. It can be separated from C. laevis by the shape of the rostrum, which is straight or slightly crested basally and not sigmoid as in C. laevis ; the smaller egg size (0.40–0.47 × 0.25–0.30 mm vs. 0.80–0.90 × 0.48–0.52 mm in C. laevis ), and the ratio of ischium to merus in the first two pereiopods (merus almost as long as ischium vs. much longer in C. laevis ). Three male specimens in the ZRC labeled as being collected from Rangoon (Yangon, Myanmar) by C. H. Fernando in the 1960s clearly belong to the present species.

Distribution. – Peninsular Malaysia, Sarawak and Myanmar (present study; Johnson, 1961).

Figures

Fig. 8. Caridina thambipillaii: A, cephalothorax and cephalic appendages; B, telson; C, distal portion of telson; D, mandible; E, maxillula; F, maxilla; G, first maxilliped; H, second maxilliped; I, third maxilliped; J, preanal carina; K, diaeresis; L, scaphocerite. Scale bars: A = 1 mm, B, D–J = 0.5 mm; C, K = 0.2 mm. (A–C, female, cl 5.9 mm, D–K, ovigerous female, cl 5.7 mm; all material from Sungai Stunggang, Sarawak, East Malaysia, ZRC).

Fig. 9. Caridina thambipillaii:A, cephalothorax and cephalic appendages; B, first pereiopod; C, second pereiopod; D, third pereiopod; E, dactylus of third pereiopod; F, basis of fourth pereiopod, showing the epipod; G, fifth pereiopod; H, dactylus of fifth pereiopod. Scale bars: A = 1 mm; B–D, F, G = 0.5 mm; E, H = 0.2 mm. (ovigerous female, cl 5.7 mm, Sungai Stunggang, Sarawak, East Malaysia, ZRC).

Fig. 10. Caridina thambipillaii: A, cephalothorax and cephalic appendages; B, first pereiopod; C, second pereiopod; D, third pereiopod; E, dactylus of third pereiopod; F, endopod of male first pleopod; G, male second pleopod. Scale bars: A = 1 mm; B–D = 0.5 mm; E – G=0.2 mm. (male, cl 3.3 mm, Sungai Stunggang, Sarawak, East Malaysia, ZRC).

Fig. 7. Caridina sumatrensis: A, cephalothorax and cephalic appendages; B, distal portion of telson; C, first pereiopod; D, second pereiopod; E, third pereiopod; F, dactylus of third pereiopod; G, fifth pereiopod; H, dactylus of fifth pereiopod; I, male first pleopod; J, male second pleopod. Scale bars: A = 1 mm; C–E, G = 0.5 mm; B, F, H, I, J = 0.2 mm. (male, cl 3.7 mm, Sungai Telor, Peninsular Malaysia, ZRC).