Pseudocleopatra togoensis Thiele, 1928

Neiber, Marco T., Kahl, Sandra M., Wiggering, Benedikt & Glaubrecht, Matthias, 2019, Adding the West-African riverine component: Revision of the Recent freshwater snails belonging to Pseudocleopatra Thiele, 1928 (Caenogastropoda, Cerithioidea, Paludomidae), Zootaxa 4674 (3), pp. 301-328 : 310-312

Pseudocleopatra togoensis Thiele, 1928

Figs 7 , 8A , 9–10

Pseudocleopatra togoensis Thiele, 1928: 394–395 , 400, 402, textfig. 58, pl. 8, figs 18, 18a (in part); Mandahl-Barth (1973: 279–281, fig. 3g); Mandahl-Barth (1974: 355–356, fig. 2a); Brown (1980: 111–112) (in part); Brown & Kristensen (1993: 28, 51); Brown (1994: 25, 128, 537, 579, figs 9g, 61f); Glaubrecht (1996: 27, 144–145, 147–148, fig. 24a, d); Van Damme & Pickford (2003: 54–55, fig. 41b); Kristensen & Stensgaard (2010b: e.T165404A6017727).

Pseudocleopatra voltana— Brown (1980: 111, fig. 63f).

Type locality. “ Fluss Volta bei Apaso ( Togo)”; Volta River in Ghana; Volta Region , Krachi East District , Apase, 7°31’33.6’’, 0°07’04.8’’ E; today inundated by Lake Volta .

Type material. Lectotype (herein designated to preserve stability of nomenclature; Fig. 7A ), ZMB 190048a (one dry shell), ZMB 190048b (one operculum) and ZMB 190048c (one radula preparation ), leg. W. Kört. The original type series contained two syntypes, the specimen here designated as the lectotype of P. togoensis and a second specimen ( ZMB 190049; one shell and preserved body; Fig. 11F ). The latter, however, actually belongs to P. voltana .

Other material examined. Ghana: “Otiso village, river Oti drift, among gravel” (= Volta Region, Krachi East District, Otiso , 7°36’36’’ N, 0°04’55’’ E, today inundated by Lake Volta), DBL 2603 ,> 25 specimens ; “White Volta River at Yapei Ferry” (= Northern Region, Central Gonja District, Yapei, White Volta, 9°08’27’’ N, 1°09’31’’ W), DBL 127 , 9 specimens ; “ Mogeyenga village, Northeastern region ” (not localised), DBL 2604 ,> 25 specimens ; “Northeast region” (= Northeastern Ghana, without exact locality), DBL 214 ,> 25 specimens . Togo: “Oti river at Bdakune village, Sunson area” (= Savanes, Sansanné-Mango area, Oti River , ca. 10°21’ N, 0°29’ E), DBL 2601 , 4 specimens .

Shell ( Fig. 7 ). The shell of P. togoensis has an elongate to depressed ovoid shape with 3–4 slightly to wellrounded whorls with sinuous growth lines and sometimes 2–3 faint spiral ridges. The colour of the shells varies from a golden yellowish brown with slightly darker brown, sinuous radial stripes to brown or olive green to dark brown without radial bands. The spire height is about ¼ to ⅓ of the total shell height; the first whorls are often eroded. The aperture is holostome and ovate, higher than wide and slightly drawn out at the upper angle; outer margin sinuous in lateral view, columella curved and the basal margin evenly rounded (in the most mature specimens slightly produced). An umbilicus present, but narrow.

Measurements (n = 88). h: 9.50 ± 1.25 mm (range: 5.6–13.6 mm); w: 6.61 ± 0.96 mm (range: 4.1–8.8 mm); bw: 8.08 ± 1.21 mm (range: 4.3–10.9 mm); la: 5.45 ± 0.72 mm (range: 3.2–7.1 mm); wa: 3.63 ± 0.54 mm (range: 2.0– 4.9 mm).

Ratios (n = 88). h/w: 1.45 ± 0.11 (range: 1.16–1.69); h/la: 1.75 ± 0.12 (range: 1.49–2.05).

Operculum ( Fig. 8A ). The operculum is corneous, with a concentric, paucispiral, rather large nucleus that can reach up to ⅔ of the maximum diameter.

Radula ( Fig. 9 , Table 2 ). The rachidian tooth is of squarish shape; its cutting edge is tapering to a slightly V-shaped tip bearing 5–6/1/5–6 denticles. The mesocone is quite prominent, being ca. ⅓ longer as well as two to three times wider than the lateral denticles. Its length may vary slightly, however, due to abrasion. The lateral teeth have relatively short but straight lateral extensions. The cutting edge bears 2–4/1/4–7 denticles with the mesocone being the largest and widest. It is two times wider and 1/3 longer than the flanking denticles and of rounded shape. Towards the outside of the lateral teeth the lengths of flanking denticles are decreasing. Inner and outer marginal teeth subequal in size and slightly curved. Both the inner and outer marginals bear 6–7 denticles each that are of approximately the same size.

Distribution ( Fig. 10 ). Pseudocleopatra togoensis is restricted to the Volta River system in Ghana and Togo where it is reported from widely separated localities, some of which are located in the area today inundated by the artificial Lake Volta, as a consequence of the completion of the Akosombo Dam in 1965 (see Gocking 2005 for a historical overview).

Remarks. Pseudocleopatra togoensis is the type species of Pseudocleopatra . In his original description Thiele (1928: 394) described two different shells from the Volta River near the village Apase that were collected by Willi Kört. Only the specimen designated as lectotype above represents the species; the other former syntype (ZMB 190049) actually belongs to P. voltana . The radula preparation of the lectotype (ZMB 190048b) by Thiele from 1928 was also examined. However, a radula ribbon could not be detected. It may have dissolved during its long storage time. The absence of denticles on the marginal teeth—as noted by Thiele (1928) —could not be confirmed. However, eight examined specimens of P. dartevellei also lacked denticles on the inner marginal teeth, while two other specimens possessed up to 18 denticles on both marginal teeth ( Table 1 ). Thus, it may be possible that P. togoensis is also polymorphic with regard to radula characters.

Pseudocleopatra togoensis can be distinguished from P. voltana by the less elongate shape and the usually smoother shell without distinct spiral sculpture. Sinuous darker radial bands were only observed in some specimens of this species. Nothing is known about the ecology of the species and new records have not become known.

Figures

FIGURE 7. Shells of Pseudocleopatra togoensis Thiele, 1928. A. Lectotype, ZMB 190048a. B. Oti River at Bdakune village, DBL 2601. C. NE-Ghana, DBL 214. D. White Volta River, DBL 12761. Scale bar: 5 mm.

FIGURE 8. Opercula of Pseudocleopatra Thiele, 1928 species. A. Lectotype of P. togoensis Thiele, 1928, ZMB 190048b. B. Paratype of Pseudocleopatra voltana Mandahl-Barth, 1973, Mogeyenga village, DBL 2591. C. Probable paratype of Pseudocleopatra dartevellei Mandahl-Barth, 1973, Matadi, DBL 2583. D. Pseudocleopatra broecki (Putzeys, 1899) n. comb., MCZ 171520. E. Lectotype of Pseudocleopatra broecki (Putzeys, 1899) n. comb., MRAC 47360. Scale bar: 1mm.

FIGURE 9. Radula of Pseudocleopatra togoensis Thiele, 1928, Ghana, NE region, DBL 214. A. Radula ribbon; scale bar: 20 μm. B. Lateral and central teeth; scale bar: 10 μm. C. Cutting edge of lateral and central teeth; scale bar: 2 μm. D. Central, lateral and marginal teeth; scale bar: 20 μm.

FIGURE 10. Known occurrence records of Pseudocleopatra togoensis Thiele, 1928 in the Volta River system. The asterisk indicates the type locality. The arrow indicates the approximate location of the Akosombo dam.

FIGURE 11. Shells of Pseudocleopatra voltana Mandahl-Barth, 1973. A. Holotype, DBL 2594-1. B. Paratype, from the type locality; DBL 2594-2. C. Paratype, from the type locality, DBL 2594-3. D. Paratype, Ghana, NE region, without exact locality, DBL 2593. E. Paratype, Mogeyenga village, DBL 2591. F. Paralectotype of Pseudocleopatra togoensis Thiele, 1928, ZMB 190049. Scale bar: 5 mm.