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

publication ID	https://doi.org/ 10.11646/zootaxa.4948.2.3
publication LSID	lsid:zoobank.org:pub:A2EC5945-DE21-4A7B-940A-8E35C3AAE7AF
DOI	https://doi.org/10.5281/zenodo.4651582
persistent identifier	https://treatment.plazi.org/id/03B087DA-7916-FFB9-E4CA-FDCAFDE2FD6A
treatment provided by	Plazi
scientific name	Sudanonautes tiko Mvogo Ndongo, Schubart & Cumberlidge
status

Treatment

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

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

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

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

Sudanonautes granulatus, Cumberlidge, 1999: 174 View in CoL , 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) View in CoL : 1 View Cited Treatment –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. GoogleMaps

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. GoogleMaps

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. GoogleMaps 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. GoogleMaps 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 GoogleMaps ). 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. GoogleMaps 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 GoogleMaps .

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 GoogleMaps .

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 View FIGURE 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 View FIGURE 6 ) (vs a G1 TA that is longer (TA/SS 0.84) in S. umaji n. sp. ( Fig. 6D, E View FIGURE 6 )); the G1 SS is slim (ratio of width of basal margin / distal margin = 2.2) in S. granulatus s.s. ( Fig. 6A, B View FIGURE 6 ) (vs a G1 SS that is broad (ratio of width of basal margin / distal margin = 4) in S. umaji n. sp. ( Fig. 6C, D View FIGURE 6 )); and the ischium of the third maxilliped has a faint vertical sulcus in S. granulatus s.s. ( Fig. 7D View FIGURE 7 ) (vs an ischium of the third maxilliped with a deep vertical sulcus in S. umaji n. sp. ( Fig. 2B View FIGURE 2 )).

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 View FIGURE 6 ) and S. umaji n. sp. ( Fig. 6D, E View FIGURE 6 ) (vs G1 SS margins that are fringed by long setae in S. koudougou n. sp. ( Fig. 7A, C View FIGURE 7 )); the anterolateral margins of the carapace are distinctly granulated in both S. granulatus s.s. ( Figs. 1A View FIGURE 1 ; 4A View FIGURE 4 ) and S. umaji n. sp. ( Fig. 2A, B View FIGURE 2 ) (vs anterolateral margins that are completely smooth in S. koudougou n. sp. ( Fig. 3A View FIGURE 3 )); an intermediate tooth that is small but pointed in both S. granulatus s.s. ( Fig. 3A View FIGURE 3 ) and S. umaji n. sp. ( Fig. 4B View FIGURE 4 ) (vs an intermediate tooth that is reduced to a granule in S. koudougou n. sp. ( Figs. 3A View FIGURE 3 , 4C View FIGURE 4 )); 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 View FIGURE 3 )); and the major chela has a dactylus that is only slightly arched with several large teeth ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 , 4B View FIGURE 4 ) (vs a major chela dactylus that is highly arched and lacks large teeth in S. koudougou n. sp. ( Figs. 3A View FIGURE 3 , 5E, F View FIGURE 5 )).

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 View FIGURE 1 , 2A View FIGURE 2 ) (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 View FIGURE 3 ) (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 View FIGURE 1 , 2A View FIGURE 2 , 3A View FIGURE 3 ) (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 View FIGURE 1 , 2A View FIGURE 2 , 3A View FIGURE 3 ) (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 View FIGURE 1 , 2A View FIGURE 2 , 3A View FIGURE 3 ) (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 View FIGURE 1 , 2A View FIGURE 2 , 3A View FIGURE 3 ) (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 View FIGURE 6 , 7A, B View FIGURE 7 ) (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 View FIGURE 1 , 2B View FIGURE 2 ) (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 View FIGURE 3 , 7E, F View FIGURE 7 ) (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 View FIGURE 6 , 7A, B View FIGURE 7 ) (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 View FIGURE 1 , 2A View FIGURE 2 , 3A View FIGURE 3 ) (vs an exorbital tooth that is large and triangular in S. sangha ( Cumberlidge & Boyko 2001: fig. 4c)).