Caridina gracilipes De Man, 1892

(Figs. 4, 5)

Caridina Wyckii var. gracilipes De Man, 1892: 387, fig. 29a–e; Schenkel, 1902: 498; J. Roux, 1904: 554.

Caridina Wyckii Henderson, 1893: 434; Nobili, 1903: 6.

Caridina nilotica var. gracilipes De Man, 1908b: 270, pl. XX, fig. 7a–b; Rathbun, 1910: 316; J. Roux, 1917: 590; Kemp, 1918: 275; Bouvier, 1925: 125; Yu, 1936: 88.

Caridina gracilipes Richard & Chandran, 1996: 246, Fig. 3; Wowor et al., 2004: 341 (key), fig. 6C, D; Cai & Shokita, 2006: 250; Mariappan & Richard, 2006: 9, figs. 5–7; Cai et al. 2007: 284; Ragunathan & Valarmathi, 2007: 95.

Caridina nilotica var. bengalensis De Man, 1908a: 226, 1908b: 265, pl. XX, fig. 6a–b; Kemp, 1915: 307; 1918: 275; Bouvier, 1925: 246.

Caridina bengalensis Mariappan & Richard, 2006: 17, figs. 8–11.

Material examined. Types: Syntypes. Indonesia. C. Wycki gracilipes, Celebes, ZMA reg. De 102634, 5♂, 9♀ ovig., 13♀, 2 damaged specimens.

Non-types: India. Caridina Wyckii, Madras, pres. & det. J. R. Henderson, NHM reg. 1892.7.15.24–31, 4♂, 7♀ ovig.

Description. Adult size 20–32 mm. Carapace length 3.5–5.5 mm.

Rostrum (Fig. 4 a–c): Rostrum slender, 1.0–1.17×long as carapace, longer than antennal scale. Dorsal margin with 12–24 proximal teeth leaving distally 0.25–0.65 unarmed. 1–3 post orbital teeth present. Tip bifid. 12–21 teeth on the ventral margin leaving a short distal margin unarmed. Formula (1–3) 12–24/12–21.

Antennular peduncle (Fig. 4 a–c): 0.65–0.75×carapace. Stylocerite 0.6–0.75×length of basal segment. Anterolateral teeth of basal segment 0.2–0.35 second segment. 10–15 segments bearing aesthetascs.

First pereiopod (Fig. 5 a): Dactylus 1.1–1.25×palm of propodus. Chela 2.0–2.6×long as broad. Carpus 1.9–2.25×long as broad with anterior excavation.

Second pereiopod (Fig. 5 b): long and slender. Dactylus 1.2–1.48×long as palm of propodus. Chela 2.3–3.0×long as broad. Carpus 5.5–6.3×long as broad.

Third pereiopod (Fig. 5 c, d): Dactylus 2.5–3.5×long as broad. 7–11 spines on dactylus including terminal spines. Propodus 3.5–5.3×long as dactylus and 9–11×long as broad with 12–16 spines along inner margin. Carpus 0.5–0.65×long as propodus, with 1 large spine and 3–5 minute spines on inner margin. Merus 1.7–2.0×carpus length. Merus with 3 large spines on posterior margin.

Fifth pereiopod (Fig. 5 e, f): Dactylus 3.3–4.3×long as broad with 55–70 spines in comb-like fashion on inner margin. Propodus 10–14×long as broad and 3.0–3.7×long as dactylus and with 12–17 spines along posterior margin. Carpus 0.5–0.65×propodus length with one large spine and 4–5 minute spines along inner margin. Merus 1.4–1.75×carpus length, with 2 large spines at posterior margin.

Setobranchs: 2 setae on all pereiopods.

First male pleopod (Fig. 5 g–i): Endopod 3.0–3.5×exopod length. One male from type specimens of C. w. gracilipes (Fig. 4 g, h) possesses appendix interna, but in other 4 males it was absent (Fig. 5 i). One male from the samples of C. wyckii of Henderson possesses appenedix interna on the endopod and other 3 males had no appendix interna.

First female pleopod: Ratio of the endopod to exopod length varies remarkably from 0.45–0.65.

Eggs (Fig. 5 j): ca. 575 eggs of 0.35–0.39× 0.19–0.23 mm size.

Second male pleopod: Appendix masculina1.5–2.0×appendix interna and 0.35–0.45×endopod.

6th abdominal somite: 0.6–0.7×long as carapace.

Telson (Fig. 5 k, l): Broad, 1.0–1.15×long as 6th abdominal somite. Dorsal spines 4–6 pairs (including subterminal spine). Posterior margin rounded or triangular with a median process, bearing 1 pair of long lateral spines and 2–4 pairs sparsely plumose long spines of equal length and shorter than lateral spines.

Uropod (Fig. 5 m): 9–12 diaeresis spinules.

Preanal carina (Fig. 5 n): Armed with a spine.

Distribution. India; Malay Peninsular; Philippines; Sulawesi (Celebes) and Borneo, Indonesia; China and Taiwan.

Type locality. Sulawesi (Celebes) and Selayar, Indonesia.

Remarks. The taxonomy of C. gracilipes is confusing owing to the number of varieties named by De Man (1892, 1908b). He (De Man 1892) originally named a species from the Celebes (now Sulawesi) and Saleyer (now Kabupaten Selayar) as Caridina wyckii (Hicks) gracilipes, but later, when dealing with C. nilotica and its varieties, De Man (1908b) assigned his specimens from Indonesia to C. n. gracilipes. In addition, while describing the fauna of brackish water ponds at Port Canning, Lower Bengal, De Man (1908a) mentioned a new variety namely C. n. bengalensis which he later described in detail (De Man 1908b). To confuse matters further, C. wyckii (Hickson) was reported from two Indian localities by Henderson (1893) at Madras and Pondicherry by Nobili (1903). But De Man (1908b) synonymised Caridina wyckii of Henderson (1893) and Nobili (1903) with C. n. bengalensis and indicated that this subspecies was different from those Caridina species that have been observed in Africa as well as the varieties that have been recorded on the Indian Archipelago. According to De Man (1908b), C. n. bengalensis presented greater resemblance to his variety C. n. gracilipes from Celebes emphasizing that the slender dactyli of the three posterior legs, the carpus of the first pereiopod being twice or little more than twice as long as broad, the shape and spinulation of the rostrum and the small eggs were the characters of the latter species. However he reiterated that C. n. gracilipes, “is most closely related to the var. bengalensis from which it seems to differ by characters of the rostrum and by its slightly smaller eggs”. De Man (1908b) thus initiated the discussion on the identification of his two varieties of C. nilotica.

Based on his observations of the numerous specimens deposited in the Indian Museum from Chilka Lake and from Shanghai, Kemp (1915, 1918) considered that C. n. bengalensis show a greater range of variation than De Man (1908b) indicated and concluded that, “ bengalensis must be regarded merely as a synonym of gracilipes ”. But Bouvier (1925) differentiated the two species on the basis of the measurements of dactylus length to propodus length of the 5th pereiopod being less than 0.25 in C. bengalensis and more than 0.25 for C. gracilipes. Richard and Chandran (1994) rejected this character on the basis of the measurements given by De Man (1908b), confirmed the conclusion of Kemp (1915, 1918), afforded species status to C. n. gracilipes and considered C. n. bengalensis as the junior synonym. However, they (Richard and Chandran 1994) indicated that male C. gracilipes from Madras as well as those from the syntype series lacked appendix interna on the first pleopod. Cai & Shokita (2006) examined the type specimens of Caridina Wyckii var. gracilipes and confirmed the species status of C. gracilipes. They indicated that the type specimens lacked appendix interna on the endopod of the first male pleopod, a matter that Marippan & Richard (2006) discussed. These authors considered naming the specimens that possessed appendix interna as C. gracilipes and those that lacked appendix interna on the first male pleopod as C. bengalensis.

The present study examined the male specimens from the syntype series of C. wyckii gracilipes (ZMA reg. De 102634, 5♂) and discovered a well developed appendix masculina with (1♂) and without (4♂) appendix interna on the endopod of first pleopod of male (Fig. 5 g, h, i). This fact was further confirmed by the examination of the specimens collected by Henderson from Madras (NHM reg. 1892.7.15.24–31) comprising 4 males. These possessed well developed appendix masculina and were with (3♂) and without (1♂) appendix interna. Therefore, the presence or absence of appendix interna is not a reliable character upon which to afford nomenclatorial status without any other differentiating characters (also see Richard & Clark 2005). Thus the present study confirms the observation of Kemp (1915, 1918), Richard & Chandran (1994) and considers C. bengalensis as a junior synonym of C. gracilipes.

Johnson (1963) considered that the C. Wyckii of Henderson (1893) and Nobili (1903), C. Wyckii var. gracilipes of J. Roux (1904), C. n. gracilipes of Rathbun (1910), J. Roux (1917), Kemp (1918), partim Bouvier (1925) and Yu (1936), and C. n. bengalensis of De Man 1908, Kemp 1915, 1918, as junior synonyms of C. simoni. Moreover, the decision by Johnson to include J. Roux 1904 is questionable since this is only a list of localities taken from De Man (1892) and Schenkel (1902) and not a morphological description. The decision of Johnson (1963) to synonymise C. gracilipes with C. simoni is not considered as valid by the present study. Based on the examination of C. wycki gracilipes syntype material and descriptions of C. n. bengalensis and C. n. gracilipes by De Man (1908a, b), J. Roux (1917), Kemp (1918) and Bouvier (1925), it is confirmed here that C. gracilipes differs from C. simoni in having rostrum with bifid tip (vs. pointed in C. simoni), 12–24 teeth proximally on the dorsal margin leaving 0.25–0.65 of the dorsal margin unarmed distally (vs. 15–25 teeth proximally leaving 0.25–0.4 of the dorsal margin unarmed distally which is interrupted by 1–4 teeth, rarely left uninterrupted in C. simoni), 1–3 post orbital teeth present (vs. 3–5 post orbital teeth in C. simoni), posterior margin of the telson rounded or triangular with a median process (vs. rounded and mostly without a median process in C. simoni) and in having ca. 575 eggs of 0.35–0.39× 0.19–0.23 mm size (vs. 50– 160 eggs of 0.65–1.0× 0.45–0.6 mm size in C. simoni)

Two De Man (1908b) species, namely C. brachydactyla and C. gracilipes, are close with respect to rostral morphology and teething. However, De Man 1908b considered these two species as distinct based on the dactylus of third pereiopod i.e., being slender in C. gracilipes (vs. stout in C. brachydactyla); the proportions of the dactylus length to propodus length of the third pereiopod i.e., 3.5–5.3 in C. gracilipes (vs. 5.7–6.5 in C. brachydactyla) and the number of eggs i.e., C. gracilipes had comparatively fewer numbers of smaller eggs ca. 575 eggs of 0.35–0.39× 0.19–0.23 mm size from this present study (vs. numerous eggs of 0.4–0.43× 0.2–0.25 mm size (ca. 850 eggs Richard & Clark 2010 in C. brachydactyla).