Caridina gaesumi, Richard & Clark, 2009

Jasmine Richard & Paul F. Clark, 2009, African Caridina (Crustacea: Decapoda: Caridea: Atyidae): redescriptions of C. africana Kingsley, 1882, C. togoensis Hilgendorf, 1893, C. natalensis Bouvier, 1925 and C. roubaudi Bouvier, 1925 with descriptions of 14 new species, Zootaxa 1995, pp. 1-75 : 57-60

Caridina gaesumi sp. nov.

( Figs. 30 , 31 )

Material examined. Holotype: ♀ ovig. Nigeria Osse River (Ovia River) near Gilli Gilli, Midwest State, 6°9.5'N 5°21'E, 16.5.1975, coll. & pres. C. B. Powell, RMNH D 30480 . Paratypes: Lagune of Ogba River, S of Ogba, Midwest State, 6°17'N 5°35'E, 16 and 22.5.1975, coll. & pres. C. B. Powell, RMNH D 30479 , 7♀ ovig., 3♀; Osse River (Ovia River) near Gilli Gilli, Midwest State; 6°9.5'N 5°21'E, 16.5.1975, coll. & pres. C. B. Powell, RMNH D 30480 , 5♀ ovig., 3♀. Republic of Zambia Irrigation ditch, Nakambala Sugar estate, Mazabula, 29.6.1981, pres. J. Pollock, NHM 1982.139, 1♂.

Description. Total length: 14–23 mm. Carapace length: 2.9–3.2 mm.

Rostrum ( Fig. 30a, b, c ): reaching apex of antennal scale. 2.4–2.8 mm in length. 0.8–0.9 × carapace. 10–20 teeth on dorsal margin leaving 0.3–0.4 of length distally unarmed sometimes interrupted by 1–2 teeth. 1–3 post-orbital teeth. 3–9 teeth on ventral margin arranged to tip. Tip pointed or bifid. Formula (1–3) 10–20/ 3–9.

Antennular peduncle ( Fig. 30d ): 0.65–0.75 × carapace. Stylocerite 0.7–0.9 × length of basal segment. Anterolateral teeth of basal segment 0.25–0.4 × second segment. 5–9 segments bearing aesthetascs.

First pereiopod ( Fig. 31a ): dactylus 1.3–1.4 × palm of propodus. Chela 2.4–2.5 × long as broad. Carpus 2.3–2.5 × long as broad with anterior excavation.

Second pereiopod ( Fig. 31b ): dactylus 1.1–1.2 × long as palm of propodus. Chela 3.1–3.3 × long as broad. Carpus 6.5–7.1 × long as broad.

Third pereiopod ( Fig. 31c, d ): dactylus 2.5–3 × long as broad.4–9 spines on dactylus (including terminal spines). Propodus 5–5.2 × long as dactylus and 13.5–15 × long as broad with 7–10 spines along posterior margin. Carpus 0.5–0.6 × long as propodus, with minute spines on inner margin. Merus 1.5–1.7 × carpus length. Merus with 4 spines on posterior margin.

Fifth pereiopod ( Fig. 31e, f ): dactylus 2.4–2.6 × long as broad with 25–45 spines arranged in comb-like fashion on inner margin. Propodus 13–14 × long as broad and 3.5–4.0 × long as dactylus with 9–12 spines along inner margin. Carpus 0.5–0.6 × propodus length and with minute spines along inner margin. Merus 1.5–1.6 × carpus length, with 2 spines along inner margin.

Setobranchs: 2 on all pereiopods.

First male pleopod ( Fig. 31g, h ): endopod 0.4 × exopod; appendix interna absent. Short setae present on margin.

First female pleopod ( Fig. 31i ): endopod 0.5–0.6 × long as exopod.

Eggs ( Fig. 31j ): 10–15, 0.9–1.1 × 0.5–0.6 mm in size.

Second male pleopod ( Fig. 31k ): appendix masculina 1.3 × appendix interna. 0.35 × endopod. Several stalked spines along posterior margin.

Sixth abdominal somite: 0.6–0.7 × long as carapace.

Telson ( Fig. 31m, n, o ): 1–1.1 × long as sixth abdominal somite. 4–5 pairs of dorsal spines (including sub terminal spines). Broad with pair of longer lateral spines almost reaching 0.6–0.9 of inner plumose process. 1–3 pairs or 3 or 5 stalked plumose processes present at posterior margin.

Uropod ( Fig. 31p ): 7–10 diaeresis spinules.

Preanal carina ( Fig. 31q ): Sharp with spine or unarmed.

Remarks. Caridina gaesumi sp. nov. is distinguished by the following characters: rostrum straight, reaching apex of antennal scale, dorsal teeth 10–20, arranged up to the tip or leaving the 0.3–0.4 of the dorsal distal margin plain, which is interrupted by teeth; 3–9 teeth on the ventral margin of the rostrum arranged from the proximal end up to the tip; tip of the rostrum pointed or bifid; 20–45 spines on the dactylus of the fifth pereiopod; few eggs in ovigerous females (10–15); and longer lateral spines on the posterior margin of the telson.

Caridina gaesumi is similar to C. togoensis in the arrangement of teeth on the dorsal margin of the rostrum, either compactly arranged up to the tip or with a short distal unarmed margin, and in bearing plumose processes at the posterior margin of the telson. However, the unarmed dorsal distal margin, when present, could be interrupted by teeth in C. gaesumi sp. nov. whereas it is plain in C. togoensis . Also the tip of the rostrum could be either pointed or bifid in C. gaesumi sp. nov. whereas it is pointed in C. togoensis . Caridiana gaesumi sp. nov. differs from C. togoensis in possessing comparatively longer lateral spines on the posterior margin of the telson.

Etymology. The specific name is derived from g aesum, Latin, meaning a long heavy javelin, referring to the distinguishing character of this species, namely the long lateral spines on the posterior margin of the telson.

Figures

FIGURE 30. Caridina gaesumi sp. nov., RMNH D 30479, ♀ ovig.: a) Entire. RMNH D 30479, ♀: b) Anterior region of cephalothorax. RMNH D 30479, ♀ ovig.: c) Anterior region of cephalothorax; d) Antennular peduncle.

FIGURE 31. Caridina gaesumi sp. nov., RMNH D 30479, ♀ ovig.: a) First pereiopod; b) Second pereiopod; c) Third pereiopod; d) Dactylus of third pereiopod; e) Fifth pereiopod; f) Dactylus of fifth pereiopod. NHM 1982.139, ♂: g) First pleopod; h) Endopod of first pleopod. ♀ ovig.: i) First pleopod; j) Eggs. NHM 1982.139, ♂: k) Second pleopod; l) Appendix masculina; m) Telson; n) Posterior margin of telson; o) Posterior margin of telson; p) Uropod diaeresis spinules; q) Preanal carina.