Sudanonautes tiko Mvogo Ndongo, Schubart & Cumberlidge

Cumberlidge, Neil, Mvogo Ndongo, Pierre A. & Clark, Paul F., 2021, Disentangling the Sudanonautes granulatus (Balss, 1929) species complex (Potamoidea: Potamonautidae), with the description of two new freshwater crabs from Nigeria and Côte d’Ivoire, West Africa, Zootaxa 4948 (2), pp. 201-220 : 209-218

Sudanonautes tiko Mvogo Ndongo, Schubart & Cumberlidge in Mvogo Ndongo, Schubart, von Rintelen, Tamesse & Cumberlidge, 2017

Sudanonautes orthostylis, Cumberlidge, 1989: 231–237 (in part), figs. 1 a–g, 2a–c; tabs. 1, 2.

Sudanonautes granulatus, Cumberlidge, 1993a: 806–807 , 812 (in part), figs. 1a, b, 2a–d, 3a–c, 4a, b.

Sudanonautes orthostylis, Cumberlidge, 1993b: 520–521 (in part), tab. 2.

Sudanonautes granulatus, Cumberlidge, 1999: 174 , 175, 198–201 (in part), figs. 31B, 32G, 33G, 34G, 35G, 36J, 37G, 39B, 53W, 54–57, 60G, 67H, tab. IX.

Sudanonautes tiko, Mvogo Ndongo et al. (2017) : 1 –11, figs. 1–4, 6.

Holotype. MNB Crust.29628, adult male ( CW 36.2 mm, CL 24.8 mm, CH 12.2 mm, FW 10.4 mm), Cameroon, Tiko, Tamba Forest , Southwest Region (4.180556N, 9.394444E), 100 m asl, 22 Aug. 2015, coll. P. A. Mvogo Ndongo.

Paratype. MNB Crust.29629, adult male ( CW 35.4 mm, CL 25.1 mm, CH 12.0 mm, FW 10.3 mm) , Cameroon, Edea, Mbus Michon , Littoral Region (3.757222N, 10.32056E), 137 m asl, 10 Jul. 2015, coll. P. A. Mvogo Ndongo.

Other material. LZUY-00, adult male ( CW 28.7 mm, CL 20.7 mm, CH 9.7 mm, FW 9.2 mm), Cameroon, Edea, Mbus Michon , Littoral Region (3.757222°N, 10.32056°E), 9 Jul. 2015, coll. P. A. Mvogo Ndongo. NHM 1938.7.1.14–23, 2 adult males (CWs 33.6, 29.8 mm), 5 subadult males (CWs 27.8, 26.7, 25.9, 24.8, 22.9 mm), 5 juv. males (CWs 18.4, 17.9, 18.4, 17.9, 17.8 mm), 3 adult females (CWs 42.8, 36.0, 29.7 mm), subadult female ( CW 20.7 mm), Cameroon, tributary of Cross River, Tinto, Asumbi , Mamfe Division , 716 m asl (5.545367°N, 9.588061°E), 1 Jul. 1938, coll. S. Sanderson. NMU 28.IV.1979 , adult male ( CW 41.5 mm), Nigeria, Oban Hills, Cross River State, Ekang (= Akansoko = MCC) Road , 25 km northeast of Calabar (5.108406°N, 8.523134°E), 28 Apr. 1979, coll. J. C. Reid ). NMU TRW 1980.02 b, adult male CW 39.6 mm, Nigeria, Cross River State, 30 km north of Calabar (5.1678128°N, 8.538973°E), 5 Mar. 1979, coll. J. C. Reid. NMU 07.2001 h, adult male ( CW 36.1 mm), 2 adult females (CWs 39.0 ovigerous, 30.1 mm), Equatorial Guinea, Bioko Island, Lago Loreto (3.407378°N, 8.673116°E), Jul. 2001 .

Diagnosis ( Mvogo Ndongo et al. 2017: figs. 1a, b, 2a–e, 3a–c). Carapace subovoid; postfrontal crest distinct, completely traversing carapace, meeting epibranchial teeth; exorbital tooth low, blunt, intermediate, epibranchial teeth both granule-sized. Vertical sulcus on branchiostegite aligned to meet anterolateral margin at epibranchial tooth. Third maxilliped exopod with long flagellum, ischium with deep vertical sulcus. Thoracic sternal suture S1/2 short, faint, S2/3 distinct, completely traversing carapace, S3/4 reduced to 2 short notches on lateral margins; margins of S1–4 thickened, raised; anterior margin of sternopleonal cavity low, not raised. Fingers of male major chela slim, elongated, fixed finger (pollex of propodus) with 2 large teeth proximally, movable finger (dactylus) distinctly arched enclosing elongated oval interspace when closed, with single large tooth one-third distance from base; cheliped carpus inner margin with 2 small pointed subequal teeth; cheliped merus lower margins both lined by small sharp teeth. G1 SS medium width (ratio of width of basal margin / distal margin = 3); G1 TA elongated (G1 TA/SS 0.33), one third length of gonopod, proximal G1 TA straight basally, distal half curving sharply outward, midsection widened, distally tapering evenly to narrow, pointed tip. G2 TA extremely short (TA/SS 0.1).

Size. A medium-sized species, adult size range CW 28–42.8 mm.

Type locality. Cameroon, Tamba Forest, Tiko , in the Southwest Region (04.180556°N, 9.394444°E), 100 m asl .

Habitat. Sudanonautes tiko is found in the humid area of the coastal rain forests bordering the Gulf of Guinea in Nigeria, Cameroon, and Bioko Island in the Northern and Southern Gulf of Guinea drainage ecoregions. Tiko (the type locality) and Edea are both in the coastal zone of Cameroon which includes volcanic highlands such as Mount Cameroon (4,095 m asl), and receives a heavy annual rainfall (exceeding 5,000 mm). Sudanonautes tiko lives under rocks in small streams at Tiko where it occurs sympatrically with other species of freshwater crabs such as S. africanus and S. floweri . At Edea, S. tiko is found under small stones in wetland areas near the Sanaga River ( Mvogo Ndongo et al. 2017).

Distribution. The present work expands the distribution of this species from two localities in the Littoral Region of southwest Cameroon (Tiko, Tamba Forest and Bwenga Forest in the Mungo River Basin, and Edea in the Sanaga River basin) to include localities in the Mamfe region of Cameroon, the adjoining Oban Hills in southeast Nigeria, and Bioko Island ( Fig. 8 ).

Remarks. The full description of this species is given in Mvogo Ndongo et al. (2017). The specimen from the Oban Hills in southeast Nigeria (NMU 28.IV.1979) that was previously identified as S. orthostylis by Cumberlidge (1989) and as S. granulatus s.l. by Cumberlidge (1993a, 1999) is reassigned here to S. tiko . Similarly, the specimen from Bioko Island, Equatorial Guinea (ZIM K5362) that was previously identified as S. granulatus s.l. by Cumberlidge (1993a), and 3 specimens from Bioko that were collected more recently (NMU 07.2001h), are also re-identified here as S. tiko .

Comparisons. The 4 new and revised taxa in the present study ( S. granulatus s.s., S. umaji n. sp., S. koudougou n. sp., and S. tiko ) can be distinguished from each other by several morphological characters. Sudanonautes granulatus s.s. from Togo is superficially similar to S. umaji n. sp. from Nigeria, but the two differ as follows. The G1 TA is short (TA/SS 0.70) in S. granulatus s.s. ( Fig. 6A, B ) (vs a G1 TA that is longer (TA/SS 0.84) in S. umaji n. sp. ( Fig. 6D, E )); the G1 SS is slim (ratio of width of basal margin / distal margin = 2.2) in S. granulatus s.s. ( Fig. 6A, B ) (vs a G1 SS that is broad (ratio of width of basal margin / distal margin = 4) in S. umaji n. sp. ( Fig. 6C, D )); and the ischium of the third maxilliped has a faint vertical sulcus in S. granulatus s.s. ( Fig. 7D ) (vs an ischium of the third maxilliped with a deep vertical sulcus in S. umaji n. sp. ( Fig. 2B )).

Sudanonautes granulatus s.s. and S. umaji n. sp. can both be distinguished from S. koudougou n. sp. from Côte d’Ivoire as follows. The mesial and lateral margins of the G1 SS are completely smooth in both S. granulatus s.s. ( Fig. 6A, B ) and S. umaji n. sp. ( Fig. 6D, E ) (vs G1 SS margins that are fringed by long setae in S. koudougou n. sp. ( Fig. 7A, C )); the anterolateral margins of the carapace are distinctly granulated in both S. granulatus s.s. ( Figs. 1A ; 4A ) and S. umaji n. sp. ( Fig. 2A, B ) (vs anterolateral margins that are completely smooth in S. koudougou n. sp. ( Fig. 3A )); an intermediate tooth that is small but pointed in both S. granulatus s.s. ( Fig. 3A ) and S. umaji n. sp. ( Fig. 4B ) (vs an intermediate tooth that is reduced to a granule in S. koudougou n. sp. ( Figs. 3A , 4C )); a carapace that is narrow and short in S. granulatus s.s. (CW/FW 3.2, CL/FW 2.2) and S. umaji n. sp. (CW/FW 2.9, CL/FW 2.0) (vs a carapace that is both wider (CW/FW 3.9) and longer (CL/FW 2.6) in S. koudougou n. sp. ( Fig. 3A )); and the major chela has a dactylus that is only slightly arched with several large teeth ( Figs. 1A , 2A , 4B ) (vs a major chela dactylus that is highly arched and lacks large teeth in S. koudougou n. sp. ( Figs. 3A , 5E, F )).

In addition, S. granulatus s.s., and S. umaji n. sp. can be distinguished from S. tiko from Cameroon, Nigeria, and Bioko by the size of the intermediate tooth between the exorbital and epibranchial teeth: it is small, distinct, and pointed in these 2 species ( Figs. 1A , 2A ) (vs reduced to a small granule in S. tiko ( Mvogo Ndongo et al. 2017: figs. 1a, 2a)). Sudanonautes koudougou n. sp. can all be distinguished from S. tiko by the postfrontal crest: it is distinct in the middle but fait at the ends in the former species ( Fig. 3A ) (vs distinct across the entire carapace in S. tiko ( Mvogo Ndongo et al. 2017: figs. 1a, 2a)).

Other Sudanonautes species. Sudanonautes granulatus s.s., S. umaji n. sp., S. koudougou n. sp., and S. tiko can all be distinguished from the 10 other West and Central African species in this genus ( S. africanus (A. Milne-Edwards, 1869), S. aubryi (H. Milne Edwards, 1853) , S. chavanesii (A. Milne-Edwards, 1886) , S. faradjensis ( Rathbun, 1921) , S. floweri (de Man, 1901) , S. kagoroensis Cumberlidge, 1991 , S. monodi ( Balss, 1929) , S. nigeria Cumberlidge, 1999 , S. orthostylis Bott, 1955 , and S. sangha Cumberlidge & Boyko, 2001 ) as follows.

The adult body size range is either small or medium (between CWs 21–58 mm), and the surface of the posterior region of the carapace is smooth in the 4 species under study here ( Figs. 1A , 2A , 3A ) (vs an adult body size range between CWs 85–90 mm, and a posterior carapace surface that is roughened with distinct warty patches and raised ridges in S. africanus ( Cumberlidge 1995b: fig. 1a; 1999: fig. 30B)). The lateral ends of the postfrontal crest meet the anterolateral margins at each of the epibranchial teeth in the 4 species under study here ( Figs. 1A , 2A , 3A ) (vs a postfrontal crest that meets the anterolateral margins behind the epibranchial teeth in S. aubryi ( Cumberlidge 1999: fig. 38A)). The epibranchial teeth are both reduced to a small granule in the 4 species under study here ( Figs. 1A , 2A , 3A ) (vs epibranchial teeth that are large and sharp in S. chavanesii ( Cumberlidge 1995c: fig. 1a; 1999: fig. 30C)). The anterolateral margin is lined by small granules in the 4 species under study here ( Figs. 1A , 2A , 3A ) (vs an anterolateral margin lined by sharp teeth in S. faradjensis ( Cumberlidge 1995d: fig. 1a; 1999: fig. 30E)).

The G1 TA is slim and is only slightly widened in the midsection in the 4 species under study here ( Figs. 6A, B, D, F , 7A, B ) (vs a G1 TA that is distinctly widened in the midsection by a ventral fold that is twice as wide as the dorsal fold in S. floweri ( Cumberlidge 1995a; 1999: fig. 38C) and in S. monodi ( Cumberlidge 1999: fig. 39A)). In addition, the carapace is medium high ( CH /FW 1.1–1.2) in the 4 species under study here (vs highly arched ( CH /FW 1.5) in S. floweri ( Cumberlidge 1995a: fig. 1b)).The outer margins of thoracic sternites S3 and S4 are thickened and in 3 of the 4 species under study here (except S. koudougou ) ( Figs. 1B , 2B ) (vs thoracic sternites S3 and S4 whose margins are flat and not raised in S. kagoroensis ( Cumberlidge 1999: fig. 32I)). The mandibular palp articulation is simple, and completely lacks a lobe or ledge in the 4 species under study here ( Figs. 3C , 7E, F ) (vs a mandibular palp with a small but distinct anterior lobe arising at the junction between the articles in S. nigeria ( Cumberlidge 1999: fig. 33J)). The G1 TA has a visible longitudinal sulcus, the midpoint of the G1 TA is curved sharply outward from the G1 SS longitudinal axis, and the distal third tapers to a pointed tip in the 4 species under study here ( Figs. 6A, B, D, F , 7A, B ) (vs a G1 TA that lacks a longitudinal sulcus, that is entirely straight, except at the tip which is curved sharply outwards in S. orthostylis ( Cumberlidge 1999: fig. 39C)). Finally, the exorbital tooth is low and blunt in the 4 species under study here ( Figs. 1A , 2A , 3A ) (vs an exorbital tooth that is large and triangular in S. sangha ( Cumberlidge & Boyko 2001: fig. 4c)).

Figures

FIGURE 1. Sudanonautes granulatus (Balss, 1929) s.s. paralectotype from Bismarckburg, Togo (MNB Crust.8977). Whole animal, A. dorsal view; B. ventral view. Scale bars: A = 9.2 mm, B = 7 mm.

FIGURE 2. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). Whole animal, A. dorsal view; B. ventral view. Scale bars: A = 8 mm, B = 4.1 mm.

FIGURE 3. Sudanonautes koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). A. whole animal, dorsal view; B. left third maxilliped, frontal view; C. left mandible, external view; D. pleon, ventral view. Scale bars: A = 23.2 mm, B, C= 4 mm, D = 7 mm. Figures A–D are based on those originally published in Cumberlidge (1993a) and are reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 4. Carapace frontal view. A. Sudanonautes granulatus (Balss, 1929) s.s. paralectotype from Bismarckburg, Togo (MNB Crust.8977); B. S. umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983); C. S. koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). Scale bars: A = 3.7 mm, B = 4.5 mm, C = 9.1 mm. Figure C was originally published in Cumberlidge (1993a) and is reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 5. Sudanonautes granulatus (Balss, 1929) s.s. paralectotype from Bismarckburg, Togo (MNB Crust.8977). A. right chela, external view; B. left chela, external view. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). C. right chela, external view; D. left chela, external view. Sudanonautes koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). E. right chela, external view; F. left chela, external view. Right cheliped carpus and merus superior view of G. S. granulatus (Balss, 1929) s.s. (MNB Crust.8977); H. S. umaji n. sp. (NMU 9.IV.1983); I. S. koudougou n. sp. (NBL CRUS.D.35256). Scale bars: A, B = 6.2 mm, C, D = 8 mm, E, F= 3 mm, G–I = 4.9 mm. Figures E, F, and I are based on those originally published in Cumberlidge (1993a) and are reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 6. Sudanonautes granulatus s.s. (Balss, 1929) paralectotype from Bismarckburg, Togo (MNB Crust.8977). A. right G1 ventral view; B. right G1 dorsal view; C. right G2 ventral view. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). D. right G1 ventral view; E. right G1 dorsal view; F. right G2 ventral view. Scale bars: A–C = 2.5 mm, D, F = 2 mm.

FIGURE 7. Sudanonautes koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). A. right G1 ventral view; B. right G1 dorsal view; C. right G2 ventral view. Sudanonautes granulatus s.s. (Balss, 1929) (MNB Crust.8977). D. left mandible, external view; E. left third maxilliped, external view. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). F. left mandible, external view. Scale bars: A, B, 2.9 mm, C = 2.5 mm, D, F = 5 mm. Figures A–C are based on those originally published in Cumberlidge (1993a) and are reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 8. Map showing the geographic distribution of Sudanonautes koudougou n. sp. (yellow square), S. granulatus s.s. (Balss, 1929) (red circles), S. umaji n. sp. (blue circles), and S. tiko (black pentagons). Scale bar = 500 km. See text for exact localities.