Caridina johnsoni, Cai & Ng & Choy, 2007

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 : 301-305

Caridina johnsoni , new species

( Figs. 15 , 16 )

Caridina tonkinensis Johnson, 1961:133 ; Figs. 16 -20; 1965: 8; Ng, 1990: 200; Ng & Choy, 1990a:16 (not C. tonkinensis Bouvier, 1919 )

Caridina propinqua – Ng, 1990: 200 (part) (not C. propinqua De Man, 1908 a )

Caridina aff. tonkinensis – Wowor et al., 2004: 343, 7M–O (not C. tonkinensis Bouvier, 1919 )

Material examined. – Holotype: ovigerous female, ZRC 1995.505 , Lower Peirce Reservoir , north arm, coll. P. K. L. Ng, Jun.1990.

Paratypes: 4 males, cl 2.5–2.7 mm, 4 females, cl 3.0– 3.2 mm, 3 ovigerous females, cl 3.3–3.5 mm, ZRC 1995.505 , Lower Peirce Reservoir , north arm, coll. P. K. L. Ng, Jun.1990 .

Others: Peninsular Malaysia: 1 ovigerous female, cl 3.4 mm, ZRC 2007.0425, Sungai Dohol, coll. H. H. Tan, 24 Feb.1995; 25 specimens (8 ovigerous), ZRC.1979.4.17.41–66, ditch at Jason Bay , Mawai-Sedili Road, 18 Feb.1960 ; 5 males, cl 2.1–2.8 mm, 16 females, cl 2.4–4.3 mm, 4 ovigerous females, cl 3.1–3.5 mm, Johor Ayer Ham, stream along Ayer Ham-Kluang road through grassy field, coll. K. Lim, 23 May 1991 ; 4 females, 3.0– 4.2 mm, ZRC 1979.4 .18.75.78, slow, small tidal, stream draining into Sungai Skudai at 71/ 2 mile, Johor Bahru-Skudai road, Johor, coll. D. S. Johnson, 10 May 1960 . Singapore: 2 females, cl 3.2–3.5 mm, 9 ovigerous females, cl 3.0– 3.4 mm, eggs 0.6 × 0.4 mm, Nee Soon Swamp forest , coll. H. K. Lua, 29 Sep.1990 ; 1 male, cl 1.9 mm, 3 females, cl 2.5–3.0 mm, 3 ovigerous females, cl 3.0– 3.4 mm, ZRC 1990.11891 – 11898 , Pasir Laba , Tengeh Reservoir, coll. K. Lim, no date , 2 males, cl 2.3–2.7 mm, 1 female, cl 3.3 mm, 3 ovigerous females, cl 3.2–3.5 mm, ZRC. 190.11835–11840, Lower Peirce Reservoir , north arm, coll. P. K. L. Ng, 21 Jul. 190 ; 1 male, cl 2.4 mm, 1 female, cl 3.0 mm, 2 ovigerous females, cl 3.2–3.4 mm, ZRC.1979.4.17.2–5, Sungai Seletar , coll. K. H. Yeo, 23 Apr.1959 ; 2 females, cl 2.5–3.4 mm, 4 ovigerous females, cl 2.9–3.8 mm, Lower Peirce Reserve , from flowing water, 28 Jul.1990 ; 5 males, cl 2.2–2.8 mm, 2 females, cl 3.3–3.4 mm, 8 ovigerous females, cl 3.6–3.8 mm, Lower Pierce Reservoir , coll. H. K. Lau, 1 Oct.1990 ; 5 males, cl 2.0– 2.2 mm, 5 females, cl 2.1–3.1 mm, 2 ovigerous females, 3.3–3.5 mm, Seletar Reservoir , coll. C. M. Yang & K. L. Yeo, no date ; 1 female, cl 2.5 mm, Lower Pierce Rd. , coll. H. K. Lau, 1 Oct.1990 ; 6 females, cl 2.2–2.9 mm, 9 ovigerous females, cl 2.5–3.4 mm, Sungai Tengeh reservoir, Pasir Laba , coll. K. Lim, 16 Nov.1990 .

Comparative material examined. – Thailand: 1 ovigerous female, cl 3.0 mm, ZRC 2007.0432 , Amphoe Chatturat , Chaiyaphum, coll. W. Noivangklang, 29 Oct.2000 ; 4 males, cl 1.7–2.1 mm, 14 females, cl 2.1–3.1 mm, 15 ovigerous females, cl 2.6–3.0 mm, eggs eyed, 0.7 × 0.4 mm, ZRC 2007.0433 , Nong Pla Tao , Chaiyaphum, coll. W. Noivangklang, 28 Oct.2000 ; 5 females, cl 2.7–3.2 mm, 13 ovigerous females, cl 2.7–2.9 mm, ZRC 2007.0434 , Nong Pla Tao , Chaiyaphum, coll. W. Noivangklang, 28 Oct.2000 ; 1 female, cl 2.2 mm, 1 ovigerous female, cl 3.0 mm, ZRC 2007.0435 , Amphoe Wang Saphung , Loei, coll. W. Noivangklang, 15 Oct.2000 ; 2 males, cl 2.5–2.8 mm, 2 females, cl 2.3–2.7 mm, 2 ovigerous females, cl 3.3–4.8 mm, ZRC 2007.0436 , Kaeng Sopha Waterfall , Phitsanulok, coll. W. Noivangklang, 11 Oct.2000 ; 1 female, cl 3.1 mm, ZRC 2007.0437 , Mae Sot, Mae Nam Moi, border with Myanmar , Karen state, 16°41.22'N 98°30.90'E, coll. H. H. Tan, 26 May 1999 ; 4 females, cl 2.8–3.0 mm, 6 ovigerous females, cl 3.0– 3.2 mm, CU 2000.04, eastern Thailand ; 1 female, cl 3.2 mm, 6 ovigerous females, cl 3.5–3.6 mm, ZRC 2007.0438 , Phitsanulok Province, Mae Nam Khet, east of Ban Bo , at km 42 on road from Phitsanulok to Loei, coll. M. Kottelat & K. Kubota, 29 Jan. 199 ; 3 females, cl 1.8–2.6 mm, ZRC 2007.0439 , artificial lake on the way to Chai Ya Pun, 82 km north of Khon Kean , with water lilies, 16°22'19.6"N 102°07'49.4"E, coll. Y. Cai & Y. Y. Goh, 20 Jun.1998 ; 2 males, cl 1.9–2.2 mm, 7 females, cl 1.8–2.7 mm, 17 ovigerous females, cl 3.0– 3.3 mm, ZRC 2007.0440 , artificial lake on the way to Chai Ya Pun, 82 km north of Khon Kean , with water lily, 16°22'19.6"N 102°07'49.4"E, coll. Y. Cai and Y. Y. Goh, 20 Jun.1998 ; 1 male, cl 2.2 mm, 1 ovigerous female, cl 3.0 mm, ZRC 2007.0441 , Mae Nam Kham River on the way to Mae Sai , 20°07'31.7"N 99°39'01.7"E, coll. Y. Cai et al., 12 Jun.1998 ; 2 males, cl 2.5–2.6 mm, 4 females, cl 2.9–3.4 mm, 8 ovigerous females, cl 3.3–3.9 mm, ZRC 2007.0442 , Mae Jio , 10 km from Chiang Mai, with water hyacinth, mud bank and substratum, warm and slightly flowing water, 18°58'25.6"N 99°14'34.1"E, pH 8.0, coll. Y. Cai, 13 Jun.1998 ; 8 males, cl 2.1–2.3 mm, 9 females, cl 3.0– 3.6 mm, 7 ovigerous females, cl 2.8–3.4 mm, ZRC 2007.0443 , Mae Lao River , 40 km from Chiang Rai, 19°58'52.6"N 99°41'46.1"E, pH 7.8, coll. Y. Cai and Y. Y. Goh, 13 Jun.1998 ; 1 ovigerous female, cl 4.0 mm, ZRC 2007.0444 , Ban Pak Som, northern Thailand , coll. Y. Cai & Y. Y. Goh, 19 Jun.1998 ; 1 male, cl 2.5 mm, 5 females, cl 2.2–2.9 mm, 14 ovigerous females, cl 3.0– 4.6 mm, ZRC 2007.0445 , Lam Thakong, outlet of dam at upper Mae Nam Mun, on the way from Sara Buri to Ratchasima , coll. Y. Cai & Y. Y. Goh, 16 Jun.1998 ; 15 males, cl 1.8–2.5 mm, 3 females, cl 2.6–3.8 mm, 5 ovigerous females, cl 3.2–3.4 mm, ZRC 2007.0446 , stream 15 km from Saraburi, outside a temple, coll. Y. Cai et al., 20 Jun.1998 ; 1 male, cl 1.9 mm, 1 female, cl 2.9 mm, 2 ovigerous females, cl 2.9–3.4 mm, ZRC 2007.0447 , southern Thailand, Narathiwat Province, Nam Tok Sipo , downstream area, 06°16.06'N 101°38.65'E, coll. H. H. Tan et al., 24 Oct. 198 ; 4 females, cl 1.9–2.5 mm, 3 ovigerous females, cl 2.8–2.9 mm, CU 2000.27, Mae Nam Pasuk , Saraburi Province, 4 Jul.1974 ; 1 ovigerous female, cl 2.5 mm, CU 2000.08, Mae Nam Mun between Buri Ram and Surin Province, 4 Nov.1974 ; 1 female, cl 3.1 mm, 1 ovigerous female, cl 3.3 mm, CU 2000.29, Thailand: Amphoe Muak Lek Waterfall , Saraburi Province, 23 Dec.1974 ; 5 females, cl 2.6–3.4 mm, 3 ovigerous females, cl 2.9–3.1 mm, CU 2000.33, Thailand; 1 female, cl 3.4 mm, CU 2000.15, Thailand : Phatchaburi Province, 2 Dec.1973 ; 1 ovigerous female, cl 2.8 mm, RMNH TH-87-87 ; 1 male, cl 2.0 mm, 5 females, cl 2.8–3.3 mm, 5 ovigerous females, cl 5.0– 5.3 mm, 0.7 × 0.5 mm, CU 2000.04, Rayong Prov., eastern Thailand , 8 Dec.1973 ; 3 males, cl 1.8–2.2 mm, 7 females, cl 2.2–3.3 mm, 9 ovigerous females, cl 2.7–3.0 mm, ZRC 2007.0448 , Mae Nam Ping River below Chiang Mai city, Nakhon Phing Bridge , 1–1.5 m in depth, 30 m in width, warm, turbid water, grass bank, mud bank and subst, slowing flowing, 10°58'25.6"N 99°14'34.1"E, pH 8.0, coll. Y. Cai et al., 13 Jun.1998 ; 3 ovigerous females, cl 2.8–3.2 mm, CU 2000.21, Thailand: Amphoe Muang , Lampang Province, 20 Aug.1973 . Borneo: West Kalimantan : 16 males, cl 2.0– 2.4 mm, 5 females, cl 2.0– 2.7 mm, 13 ovigerous females, cl 2.7–3.2 mm, ZRC 2007.0449 , Kalimantan Barat, Kabupaten Pontianak: Sungai Belado , clear water hill stream at base of Gg. Semahung, ca. 13.8 km into side road from Pahuman, coll. H. H. Tan et al., 28 Apr.1998 ; 11 males, cl 2.6–2.8 mm, 14 females, cl 2.3–2.8 mm, ZRC 2007.0450 , Kalimantan Barat, Kabupaten Pontianak: Sungai Belado , clear water hill stream ar base of Gg. Kloncet at km 67 Pontianak on Pontianak-Anjungan road, Kg. Anjungan pH 6.6, coll. H. H. Tan et al. 28 Apr.1998 .

Caridina tonkinensis Bouvier, 1919 : Vietnam: Syntype: 1 female, cl 3.3 mm, MNHN Na 918, Tonkin, coll. Sollaud, no date. Eastern Thailand: 1 female, cl 3.4 mm, ZRC 2007.0451 , Nong Khai Province, Mekong Basin: Bung Nong Suang, east of road from Nong Kai to Bung Kan at km 50, coll. M. Kottelat & K. Kubota, 2 Feb.1999 ; 1 female, cl 3.6 mm, ZRC 2007.0452 , Ban Nan Khaisat, artificial lake for rice field, 50 km to Bung Kan, 18°13'26.2"N 104°02'07.1"E, coll. Y. Cai & Y. Y. Goh, 18 Jun.1998 .

Description. – Rostrum ( Fig. 15A ) sigmoid, reaching slightly beyond end of basal segment of antennular peduncle, or near end of second segment, not beyond this segment, rostral formula 3–4+10–17/0–4(1–2). Suborbital angle acute, distinctly separated from antennal spines; pterygostomian margin subrectangular.

Sixth abdominal somite 1.7 times as long as high, 0.7 times of carapace, 1.8 times as long as fifth somite, slightly shorter than telson. Telson ( Figs. 15B, C ) 3.4 times as long as wide, distal margin rounded, not terminating in a projection, with 4 pairs of dorsal spinules and a pair of dorsolateral spinules; distal end with 4–8 pairs of spines, lateral pair longer than intermediate pairs. Preanal carina ( Fig. 15K ) low, without spine.

Eyes well developed, anterior end reaching to 0.8 times length of basal segment of antennular peduncle. Antennular peduncle 0.8 times as long as carapace; basal segment of antennular peduncle longer than combined length of second and third segments, anterolateral angle reaching to 0.3 times length of the second segment, second segment distinctly longer than third segment. Stylocerite reaching to 0.8 times length of basal segment of antennular peduncle. Scaphocerite ( Fig. 15D ) 3.4 times as long as wide.

Incisor process of mandible ( Fig. 15E ) ending in irregular teeth, molar process truncated. Lower lacinia of maxillula ( Fig. 15F ) broadly rounded, subtriangular, upper lacinia elongated, with numerous distinct teeth on inner margin, palp slender. Upper endites of maxilla ( Fig. 15G ) subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. Palp of first maxilliped ( Fig. 15H ) ending in a triangular projection. Second maxilliped ( Fig. 15I ) typical, arthrobranch well developed. Third maxilliped ( Fig. 15J ) reaching to end of second segment of antennular peduncle, with ultimate segment shorter than penultimate segment.

Epipods well developed on first 2 pereiopods, reduced in third pereiopod, absent in last 2. First pereiopod ( Fig. 16A ) reaching near anterior end of basal segment of antennular peduncle; merus 2.2 times as long as broad, distinctly shorter than carpus; carpus excavated anteriorly, shorter than chela, 2.9 times as long as high; chela 2.6 times as long as broad; fingers 1.5 times as long as palm. Second pereiopod ( Fig. 16B ) reaching to end of second segment of antennular peduncle; merus distinctly shorter than carpus, 4.0 times as long as broad; carpus 1.3 times as long as chela, 6.0 times as long as high; chela 4.0 times as long as broad; fingers 1.6 times as long as palm. Third pereiopod ( Figs. 16C, D ) reaching to end of antennular peduncle, propodus 11 times as long as broad, 2.9 times as long as dactylus; dactylus 4.6 times as long as wide (spines included), terminating in a claw, with 6 or 7 accessory spines on flexor margin. Fifth pereiopod ( Figs. 16E, F ) reaching beyond end of basal segment of antennular peduncle, propodus 12 times as long as broad, 2.3 times as long as dactylus; dactylus slender, 5.2 times as long as wide (spinules included), terminating in a claw, with 55–69 spinules on flexor margin.

Endopod of male first pleopod ( Fig. 16 G ) subtriangular, 2.3 times as long as wide, reaching to 0.25 times length of endopod, no appendix interna. Appendix masculina of male second pleopod ( Fig. 16H ) slender, reaching to half length of exopod.

Uropodal diaeresis ( Fig. 16L ) with 11–13 movable spinules.

Ovigerous females with eggs sized 0.60 × 0.40 mm.

Etymology. – The species is named after the late Dr D. S. Johnson, who was a major contributor to our knowledge of freshwater shrimps of the Malay Peninsula.

Habitat. – Various freshwater habitats: reservoirs, lakes, rivers and streams.

Remarks. – With respect to the form of the rostrum and the ratio of various joints in the pereiopods, C. johnsoni is most similar to C. tonkinesis . It can be distinguished from C. tonkinensis by the absence of a preanal spine and the relatively stouter first two pereiopods (carpus of the first two pereiopod 2.9 times and 4.0 times as long as high, respectively vs. 3.5 times and 4.4 times, respectively).

Johnson (1961) was the first to record C. tonkinensis from Singapore. This was followed by Ng (1990) and Ng & Choy (1990a). Johnson (1961: 134,135) noted a number of differences in morphological details, e.g. the relatively shorter rostrum, the shorter antennular peduncle, the stouter carpus on the first pereiopods, etc. He, however, regarded these differences as mere variation between the type [from Tonkin, Vietnam (= northern Vietnam)] and the local populations. However, close examination of specimens from various localities in Singapore and Peninsular Malaysia, including some which had been identified by Johnson (ZRC 1979.4.18.75.78), revealed that they are not C. tonkinensis and these are herein described as a new species, C. johnsoni .

Ng (1990: 200) discussed the taxonomy and ecology of what he believed to be C. propinqua , stating that “It is relatively easy to recognize because of its slender appearance and the sixth abdominal segment being much longer than those of related species. The author has obtained large numbers of this prawn from Lower Pierce Reservoir. It seems to prefer relatively shallow, clear, flowing water, being especially common among submerged plants by the bank, near the mouths of streams draining into the reservoir.” The characters of a slender appearance and the long sixth abdominal segment are shared by C. propinqua and C. johnsoni , and a re-examination of Ng’s specimens from Lower Pierce Reservoir reveals that they are C. johnsoni instead.

Distribution. – Malay Peninsula and West Kalimantan.

Figures

Fig. 15. Caridina johnsoni, new species: A, cephalothorax and cephalic appendages; B, telson; C, distal portion of telson; D, scaphocerite; E, mandible; F, maxillula; G, maxilla; H, first maxilliped; I, second maxilliped; J, third maxilliped; K, preanal carina; L, uropodal diaeresis. Scale bars: A, D = 1 mm; B, E–K = 0.5 mm; C, L = 0.2 mm. (ovigerous female, cl 3.3 mm, holotype, Lower Peirce Reservoir, ZRC).

Fig. 16. Caridina johnsoni, new species: A, first pereiopod; B, second pereiopod; C, third pereiopod; D, dactylus of third pereiopod; E. fifth pereiopod; F, dactylus of fifth pereiopod; G, male first pleopod; H, male second pleopod. Scale bars: A–C, E = 0.5 mm; D, F = 0.1 mm; G, H = 0.2 mm. (A–F, ovigerous female, cl 3.3 mm, holotype; G, H, male, cl 2.5 mm, Lower Peirce Reservoir, ZRC).