Caridina brachydactyla De Man 1908
Creators: name: Richard, Jasmine
name: Clark, Paul F.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Atyidae
Caridina
Caridina brachydactyla

description: Caridina brachydactyla De Man, 1908
(Fig. 3)
Caridina wyckii De Man, 1892: 386 (partim), pl. 24, fig. 29f.
Caridina nilotica var. brachydactyla De Man, 1908: 269, pl. 20, fig. 8a–c;? Johnson, 1961a: 123.
Caridina nilotica var. meridionalis. Reik 1953: 117, fig. 6.
Caridina brachydactyla.? Johnson, 1960a: 178; 1960b: 266; 1963: 21; Richard & Clark, 2010: 317, figs. 7–8 (for full synonymy).
Caridina meridionalis J. Roux, 1926b: 246 (partim).
Caridina brachydactyla brachydactyla Tiwari & Pillai, 1971:80, fig.1.
Nec Caridina wyckii De Man, 1892: 386 (partim), fig. 29g (= undescribed species A, see Richard & Clark, 2010: fig. 9a–c).
Nec Caridina wyckii De Man, 1892: 386 (partim), pl. 24, fig. 29i–ii. (= undescribed species B, see Richard & Clark, 2010: fig. 9d–e).
Material examined. Types: C. nilotica var. brachydactyla, Indonesia. Lectotype. 1♂ (with rostral formula (2) 19 + 1/23), Paralectotypes. 4♂, 1♀ ovig., by Reo, Flores, RMNH reg. Coll NR 977; 2♀ ovig., river near Palopa Luwu, Celebes (Sulawesi), coll. Max Webber, RMNH reg. Coll NR 2552.
Non types:? Madagascar. det. E.L. Bouvier 1918, received from E.L. Bouvier Jan. 1920, NHM not registered, 2♂, 5♀ ovig., 5♀.
Other material: Caridina nilotica var. meridionalis. Types: Cotype. Australia. Cari Creek at Cook Town, N. Queensland; exch. with Sydney; coll. A.R. McCulloch, May 1918; originally P.4296, now NMB reg. 4.VIII. a 1♂, 1♀ ovig., 2♀.
Distribution. Celebes (Sulawesi), Indonesia; Andaman Islands; South Africa, Madagascar and Australia.
Type locality. Celebes (Sulawesi) Selayar and Flores, Indonesia.
Remarks. While studying Caridina niliotica and its varieties, De Man (1908) described C. n. var. brachydactyla from specimens that he earlier considered as the typical form of Caridina wyckii (Hickson). The new variety was characterised by the slender carpus of the first pereiopod and the stout dactylus (1/6th of the propodus) of the three posterior legs. Later, Tiwari and Pillai (1971) considered C. n. brachydactyla to be a distinct species thereby rejecting the decision of Johnson (1963) to make this subspecies a junior synonym of C. simoni.
Richard & Clark (2010), who reported and described C. brachydactyla from South Africa, supported the decision of Tiwari & Pillai (1971) and considered this species to be distinct from C. simoni. They (Richard & Clark 2010) synonymised the following taxa as junior synonyms of C. brachydactyla: C. wyckii of De Man 1892, C. n. var. brachydactyla of De Man 1908, C. n. var. brachydactyla of Johnson 1961a, C. brachydactyla of Bouvier 1913a, C. brachydactyla of Johnson 1960a, b and C. n. var. natalensis of De Man, 1908.
Caridina brachydactyla can be distinguished from C. simoni by possessing a bifid tipped rostrum (vs. terminating in a pointed tip in C. simoni), teeth placed proximally leaving 0.3–0.75 of dorsal rostral margin unarmed distally (vs. 0.25–0.4 unarmed distally or interrupted by 1–4 teeth in C. simoni), 12–25 teeth from proximal end either up to the tip or with a short unarmed end distally (vs. 5–14 teeth proximally leaving the distal ventral margin always unarmed in C. simoni), posterior margin of telson triangular and with a median protuberance (vs. rounded posterior margin mostly devoid of a median protuberance in C. simoni) and in carrying ca. 850 eggs of 0.35–0.41× 0.2–0.23 mm size (vs. ca. 50– 160 eggs of 0.65–1.0× 0.45–0.6 mm size in C. simoni).
Jean Roux (1926a, b) described Caridina meridionalis from New Caledonia and Australia and the present study examined the type specimens. As rightly pointed out by Roux, 1926b the specimens from a Creek at Cook Town, Queensland, Australia have a “rostrum mostly without teeth on the distal part of the upper border” and “It is usually devoid of teeth on a longer or shorter distal part of the upper border (about 1/3)” and the ovigerous female carries “numerous eggs”. The size of eggs differs fractionally from measurement of Roux (1926b) i.e., 0.36–0.39× 0.21–0.23 mm being 0.4–0.43× 0.2–0.25 mm size. The specimens described by Roux (1926b) from a creek at Cook Town have the following characters: rostrum reaching the end of the antennal scale or slightly longer; 11–19 teeth on the proximal dorsal margin leaving 0.45–0.6 of the dorsal margin unarmed distally; 2 postorbital teeth; tip bifid; 11–16 teeth on the ventral margin either up to the tip or with a short unarmed margin distally; first pereiopod dactylus 1.2–1.5×palm of propodus; chela 2–2.2×long as broad and carpus 1.8–2.0×long as broad, with the anterior excavation; second pereiopod-dactylus 1.2–1.4×long as palm of propodus, chela 2.6–2.8×long as broad and carpus 5.0–5.6×long as broad; third pereiopod-dactylus 2.4–2.6×long as broad, 6–8 spines on dactylus (including terminal spines), propodus 5.7–6.5×long as dactylus and 10.5–14×long as broad with 14–19 spines arranged along inner margin, carpus 0.5–0.6×long as propodus, with 1 large spine and 2–4 small spines on inner margin, merus 1.9–2.0×carpus length, merus with 3 large spines along posterior margin; fifth pereiopod, dactylus 3.6–4.0×long as broad with 60–75 spines arranged in comb-like fashion on inner margin, propodus14–15×long as broad and 4.5–5.0×long as dactylus with 16–19 spines arranged along posterior margin, carpus 0.45–0.56×propodus length and with 4 large spines and 4–5 minute spines along inner margin, merus 1.5–1.6×carpus length, with 2 large spines along posterior margin; first male pleopod with endopod 0.2–0.25×exopod length, without appendix interna; numerous eggs of 0.4–0.43× 0.2–0.25 mm size; posterior margin with triangular median process, bearing 1 pair of long lateral spines and 2 pairs intermediate spines that are shorter than lateral spines; the inner pair of spines longer than the outer and 12–15 uropod diaeresis spinules present. Based on the structure of the rostrum, posterior margin of the telson and the presence of numerous eggs, the specimens from the creek at Cook Town, are here identified as C. brachydactyla.
Caridina meridionalis differs from C. brachydactyla (see Richard & Clark 2010) by the morphology of rostrum that is equal to antennular peduncle or slightly longer (vs. equal to longer than the antennal scale in C. brachydactyla) 19–27 teeth on the dorsal margin up to the tip of the rostrum of which the proximal teeth are compact and the distal 1–5 teeth spaced (vs. 12–25 teeth proximally leaving distal dorsal margin always unarmed in C. brachydactyla), 4–10 teeth on the ventral margin up to the tip or with a short unarmed end distally (vs. 12–25 teeth either up to the tip or with a short unarmed end in C. brachydactyla) and in possessing ca. 300 eggs of 0.6–0.65× 0.35–0.39 mm size (vs. ca. 850 eggs of 0.35–0.41× 0.2–0.23 mm size in C. brachydactyla).
The references by Johnson to C. nilotica var. brachydactyla (see Johnson 1961a) and C. brachydactyla (see Johnson 1960a, b; 1963: 21) are questioned in the synonymy presented above because he (Johnson 1961a: 23) synonymises C. b. subsp. peninsularis with C. brachydactyla, a decision rejected by the present study as these two species are considered as distinct. Therefore, the reference of Johnson (1961a) could have been to either of these two species. Moreover, Johnson (1960b: 266) states “If however attention is confined to limited geographical areas, it is found that these are inhabited by one or two quiet distinct forms which show little infra-specific variation. The majority of these local forms would appear to be true geographical races of the single species C. brachydactyla. This species is readily distinguishable from true C. nilotica by a number of features of which detailed armature of the 3rd thoracic leg is the most characteristic and constant”. For the present study there are many features that distinguish C. nilotica from C. brachydactyla including posterior margin of the telson, and number and size of eggs. However, the detailed armature of the 3rd pereiopod is not regarded as a good character for separating these two species. Consequently the identification by Johnson of C. nilotica and C. brachydactyla is considered doubtful. With respect to the latter species Johnson (1963: 23) writes “In the British Museum there is a specimen from Madagascar which Bouvier has identified as belonging to C. brachydactyla. I am very doubtful about this identification”. Johnson then discusses various characters of this specimen including the rostrum which he considers “differs strikingly from any rostral forms found in authentic specimens of C. brachydactyla, being much longer and with a very long unarmed portion of the dorsal margin”. Specimens of C. brachydactyla, determined by E.L. Bouvier 1918, received from him in January 1920 are extant in the NHM reference collection. There are no locality details on the label, the material has not been registered and comprises 2♂, 5♀ ovig., 5♀. Two of these specimens were placed in individual tubes, a female and an ovigerous specimen. This material was examined and the posterior margin of the telson had been cleanly removed from every specimen. The ovigerous female placed in a separate tube seemed to fit the rostral description of Johnston (1963) and the unarmed portion of the dorsal margin is 0.52. This portion is considered to be “long” and falls within the range for the species. Furthermore, the eggs of another female were measured and counted. These were small, measuring 0.35–0.4× 0.2–0.23mm in size and 885 in number. The eggs too were within the range expected for C. brachydactyla. Furthermore with reference to distribution, Johnson (1960a: 178) says “An interesting member of the group is Caridina brachydactyla which, though comparatively intolerant of salt water and normally confined to freshwaters, is nevertheless widely distributed from Papuasia and N. Australia to Siam; it does not seem to have reached India. ….”. Although the distribution data presented by Johnson is correct for C. brachydactyla, his identification of the species could be questionable.
description: Published as part of Richard, Jasmine & Clark, Paul F., 2014, Caridina simoni Bouvier, 1904 (Crustacea: Decapoda: Caridea: Atyoidea: Atyidae) and the synonymy by Johnson, 1963, pp. 301-338 in Zootaxa 3841 (3) on pages 308-310, DOI: 10.11646/zootaxa.3841.3.1, http://zenodo.org/record/228244