Sudanonautes umaji, Cumberlidge & Mvogo Ndongo & Clark, 2021

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 : 205-207

Sudanonautes umaji n. sp.

( Figs. 2A, B , 4B , 5C, D, H , 6D, F , 7F , 8 )

Sudanonautes orthostylis, Cumberlidge, 1989: 231–232 , 239–240 (in part), tabs. 1, 2.

Sudanonautes granulatus, Cumberlidge, 1993a: 806 , 810 (in part), figs. 3 h-j, 4e, f.

Holotype. NMU 9.IV.1983, adult male ( CW 27.6 , CL 18.3, CH 9.0, FW 9.0 mm, P1 propodus length × height: R 29.8 × 11.0 mm, L 19.5 × 6.0 mm), Nigeria, Umaji, 12 km north-west of Obudu Cattle Ranch , 281 m asl (6.481086°N, 9.251100°E), Amire u Kiriki River, tributary of Katsina-Ala and Benue Rivers, 9 Apr. 1983, coll. N. Cumberlidge.

Paratypes. NMU 9.IV.1983 , adult male ( CW 25.0, CL 17.8, CH 8.6, FW 8.6 mm), 3 subadult females ( CW 21.9 , CL 16.1 mm, chela propodus length × height: right 13.5 × 4.0 mm, left 13.0 × 4.0 mm, CW 20.9, CL 15.2 mm, CW 20.8, CL 15.4 mm), juvenile female ( CW 18.0, CL 13.2 mm), Nigeria, Umaji, 12 km northwest of Obudu Cattle Ranch , 281 m asl (6.481086°N, 9.251100°E), Amire u Kiriki River, a tributary of the Katsina-Ala and Benue Rivers, 9 Apr. 1983, coll. N. Cumberlidge.

Other material. NMU 5. VI.1979, adult male ( CW 34.66 mm), subadult female ( CW 21.65 mm), Nigeria, Oban Hills , Ekang Road, 30 km northeast of Calabar (5.1448315°N, 8.5245183°E), 5 Jun. 1979, coll. J. C. Reid. NMU 29. VI.1979, adult male ( CW 23.56 mm), Nigeria, Oban Hills , Ekang Road, 30 km northeast of Calabar (5.1448315°N, 8.5245183°E), 29 Jun. 1979, coll. J. C. Reid. NMU 3.VIII.1980 , adult male ( CW 30.02 mm), Nigeria, Oban Hills , Ayip-Eku Oil Palm Estate , between Osomba and New Ndebezi villages (5.4000°N, 8.7000°E), 3 Aug. 1980, coll. J. C. Reid.

Diagnosis. Carapace: surface smooth, anterolateral margins, suborbital margins, postfrontal crest all granulated. Exorbital tooth low, broad, intermediate tooth pointed, smaller than exorbital tooth, epibranchial tooth reduced to granule; vertical sulcus on branchiostegite in line with intermediate tooth, dorsal part curving posteriorly just before meeting anterolateral margin at epibranchial tooth ( Figs. 2B , 4B ). Mandibular palp with 2 articles, terminal article simple, article junction with fringe of long setae, but lacking either anterior lobe or ledge ( Fig. 7F ); third maxilliped with flagellum on exopod, ischium with deep vertical sulcus ( Fig. 2B ). Chelipeds: movable finger (dactylus) of major chela broadened, slightly arched, enclosing long narrow interspace when closed; fixed finger (pollex of propodus) of chela with 2 large sharp teeth proximally, otherwise small teeth distally ( Fig. 5C, D ); lower margin of propodus of major chela longer than CW; cheliped carpus inner margin distal tooth large, pointed, proximal tooth small ( Figs. 2A , 5H ). Gonopods: G1 TA long (TA/SS 0.84), initially angled outwards at 17° to G1 SS longitudinal axis, midpoint curved sharply outwards at 70° to G1 SS longitudinal axis; G1 TA slim, midsection only slightly widened ( Fig. 6D, E ); TA with longitudinal sulcus running to tip, visible on ventral side on proximal two-thirds, entire groove visible only if gonopod turned to superior view ( Fig. 6F ). G2 TA extremely short (TA/SS 0.14).

Description. Adult male holotype. Carapace. Cephalothorax ovoid, width about 3 × FW (CW/FW 2.9), length 2 × FW (CL/FW 2.0), medium height, subequal to FW ( CH /FW 1.1) ( Fig. 2A ). Anterior margin of front straight, curving under; carapace posterior margin width about two-thirds CW. Carapace surface smooth, lacking granules or carinae; anterolateral, suborbital margins each lined by row of small granules; postfrontal crest distinct, granulated, complete, meeting anterolateral margins; mid-groove of crest broad, shallow. Exorbital tooth low, broad, intermediate tooth distinct, small, about half size of exorbital tooth, epibranchial tooth reduced to granule ( Fig. 2A ); branchiostegite with longitudinal sulcus beginning at respiratory opening, curving backwards, dividing suborbital, subhepatic regions from pterygostomial region; vertical sulcus on branchiostegite in line with intermediate tooth, top part curving backwards just before meeting anterolateral margin at epibranchial tooth; vertical sulcus dividing suborbital from subhepatic regions ( Figs. 2B , 4B ).

Thoracic sternum. Sternal suture S1/2 faint complete; S2/3 deep, completely traversing sternum; S3/4 reduced to 2 small side notches, outer margins of S4 thickened, raised ( Fig. 2B ). Third maxillipeds filling entire oral field, except for transversely oval efferent respiratory openings; exopod with long flagellum, ischium with deep vertical sulcus ( Fig. 4B ). Mandibular palp with 2 articles, terminal article simple, article junction with fringe of long setae, but lacking either anterior lobe or ledge ( Fig. 7F ). First 5 pleomeres of male pleon (A1–5) broad, short, tapering inward; A6 long, narrow, telson triangular, tip rounded. Mature female pleon wide with oval outline, telson reaching S1/2, sides reaching coxae of P2–5, A6 longest, A5 widest, maximum width along A6–5 junction.

Pereiopods. P1 chelae unequal, right (major) longer, higher than left ( Fig. 5C, D ); P1 right propodus longer (29.8 mm) than CW (27. 6 mm); movable finger (dactylus) of right chela broadened, slightly arched, enclosing elongated oval interspace when closed, one large tooth in proximal third, rest with small teeth along cutting edge ( Fig. 5C ); movable finger (pollex of propodus) of right chela with 2 large pointed teeth proximally, small teeth distally ( Fig. 5C ). Cheliped merus lower margins both lined by small teeth, distal meral tooth larger, pointed ( Fig. 2A ). Cheliped carpus inner margin distal tooth large spine, proximal tooth small, 1/3 rd size of distal tooth ( Figs. 2A , 5H ). P2–5 neither elongated or shortened, P5 shortest leg; dactyli P2–5 tapering to point, each bearing rows of downward-pointing sharp bristles; P5 dactylus shortest article ( Fig. 2A ).

Gonopods. G1 TA long (TA/SS 0.84), initially angled outward at 17° to G1 SS longitudinal axis, midpoint curved sharply outward at 70° to G1 SS longitudinal axis; G1 TA midsection only slightly widened ( Fig. 6D, E ); G1 TA with longitudinal sulcus running from base to tip visible on ventral side in proximal two-thirds, entire groove visible only if gonopod turned to superior view ( Fig. 6F ). G1 SS widest at base, narrowest distally, slim, tapering evenly to TA-SS junction (ratio of width of basal margin / distal margin = 4); mesial, lateral margins of G1 SS completely smooth; G1 SS distal margin straight ventrally, with V-shaped indentation dorsally; G1 SS ventral side with slim flap folded inward, distally almost meeting outer margin, angled diagonally downwards, leaving heavily setose ventral side of G1 SS exposed ( Fig. 6A ). G2 shorter than G1 (G2 only reaching G1 TA-SS junction). G2 TA extremely short (G2 TA/SS 0.14); G2 SS widest at base, tapering sharply inward about one-third along length, last two-thirds forming long, thin, tapering, upright process supporting short G2 TA.

Size. Small species, adult size range CW 24–34.7 mm.

Type locality. Nigeria, Cross River State, Umaji, 12 km northwest of Obudu Cattle Ranch , 281 m asl (6.481086°N, 9.251100°E), Amire u Kiriki River, a tributary of the Katsina-Ala and Benue Rivers.

Etymology. The species is named for Umaji in Cross River State, southeast Nigeria where it was collected. The species epithet is used as a noun in apposition.

Distribution. Cross River State, southeast Nigeria ( Fig. 8 ).

Habitat. Umaji in southeast Nigeria lies in the Northern Gulf of Guinea Drainages; Bioko Freshwater Ecoregion 518 ( Thieme et al. 2005; Abell et al. 2008) in the evergreen rainforest zone that also includes parts of the Cameroon highlands and the mountain forests of Bioko Island, Equatorial Guinea. This area receives over 10 m of rainfall annually, and its aquatic systems include the Cross River basin in Nigeria, and the coastal rivers and streams that flow into the Gulf of Guinea from Cameroon and Bioko Island. Crabs were collected from under stones in a sandy, gravelly river bed. The river had been temporarily dammed by villagers so that crabs could be collected from the exposed dry river bed, after which the river flow was restored. Sudanonautes umaji n. sp. was collected at this locality together with specimens of S. africanus and S. aubryi . Several of the localities where this species occurs are in the Oban Hills, some of which are part of the Cross River National Park. This area is heavily forested and borders with equatorial rainforests in neighboring Cameroon.

Figures

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 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.