Auchenoglanis biscutatus ( Geoffroy Saint-Hilaire, 1809 )

Geerinckx, Tom & Vreven, Emmanuel, 2013, A re-evaluation of the species-level diversity within the catfish genus Auchenoglanis (Siluriformes: Claroteidae), Journal of Natural History 47 (47 - 48), pp. 2979-3010 : 3000-3002

Auchenoglanis biscutatus ( Geoffroy Saint-Hilaire, 1809)

( Figure 8A )

Pimelodus biscutatus Geoffroy Saint-Hilaire 1809

Auchenoglanis senegali Retzer 2010

Material examined

Holotype. MNHN 8969 : Nile; 285 mm SL.

Other material. Specimens are listed per river basin (from west to east).

Senegal basin . MRAC 79-2-P-211 (holotype of A. senegalensis ): camp Djoudj, Gorom River, Senegal; 16 ◦ 22 ′ N, 16 ◦ 16 ′ W; 156 mm SL. MRAC 79-2-P-212–214 (paratypes of A. senegalensis ): same locality; 3 spm, 152–171 mm SL. MRAC 80-1-P-99: same locality; 217 mm SL. MRAC 73-5-P-2814 (paratype of A. senegalensis ): Mbane, Lac de Guiers, Senegal; 16 ◦ 16 ′ N, 15 ◦ 48 ′ W; 117 mm SL.

Gambia basin . MRAC 81-3-P-381 (paratype of A. senegalensis ): Ba-Foula-Bé, Gambia River, Senegal; 13 ◦ 02 ′ N, 13 ◦ 12 ′ W; 154 mm SL.

Niger basin . MRAC 73-12 -P-366: Mopti Nord (chenal domestique), Niger River, Mali; 14 ◦ 30 ′ N, 4 ◦ 12 ′ W; 160 mm SL . MRAC 73-12 -P-367–368: Mopti Sud (aval grille), Niger River, Mali; c.14 ◦ 30 ′ N, 4 ◦ 12 ′ W; 2 spm, 156–160 mm SL . MRAC 91-67 -P- 161: Okoso Creek (sandy floodplain channel), Niger River, Nigeria; 5 ◦ 08 ′ N, 6 ◦ 23 ′ E; 180 mm SL . MRAC 73-15 -P-995–998: Garoua , Benoué River, Cameroon; 9 ◦ 18 ′ N, 13 ◦ 24 ′ E; 4 spm, 161–179 mm SL .

Chad basin . MRAC 153906–907 : Bahr-Sara, mouth of Mandoul River , Chad; c.08 ◦ 20 ′ N, 17 ◦ 46 ′ E; 2 spm, 133–145 mm SL. MRAC 154048–154050 : Bahr-Tinga, Parc de Zakouma , Chad; c.10 ◦ 50 ′ N, 19 ◦ 45 ′ E; 3 spm, 145–216 mm SL. MRAC 154094 : Fort Archambault, Chari River , Chad; 9 ◦ 09 ′ N, 18 ◦ 23 ′ E; 156 mm SL. MRAC 154174–175 : Lake Iro, Chari River , Chad; 10 ◦ 09 ′ N, 19 ◦ 23 ′ E; 2 spm, 171–214 mm SL. MRAC 19980 : Soueram , Chad; c.12 ◦ 28 ′ N, 14 ◦ 11 ′ E; 144 mm SL. MRAC 73- 26 -P-545–546: south of Hollom , Chad; c.11 ◦ 19 ′ N, 15 ◦ 04 ′ E; 2 spm, 211–223 mm SL. MRAC 73-15 -P-999–1000: Waza (bought) , Cameroon; 11 ◦ 24 ′ N, 14 ◦ 34 ′ E; 2 spm, 137–149 mm SL. MRAC 73-15 -P-989–991: Guemé, Logone River , Cameroon; 10 ◦ 30 ′ N, 15 ◦ 11 ′ E; 2 spm, 111–176 mm SL. MRAC 73-15 -P-992: same locality; 199 mm SL. MRAC 73-15 -P-994: same locality; 154 mm SL. MRAC 73-16 -P-5488: Yagoua, Logone River (bought) , Cameroon; 10 ◦ 21 ′ N, 15 ◦ 17 ′ E; 203 mm SL.

Diagnosis

Auchenoglanis biscutatus can be diagnosed from A. occidentalis by the large horizontal distance between the eye and the end of the supraoccipital process, being larger than the horizontal distance between the snout tip and the eye (104% or more; Figure 1C ). Its adipose fin rises abruptly (versus very gradually). The tip of the maxillary barbel is not darker than the head.

Description

Head deep, with short, slightly pointed snout. Maxillary barbel always reaching eye, or even beyond it. Adipose fin high, at 8–12% SL. Branchiostegal membranes not fused; 9–10(11) branchiostegal rays. Width of premaxillary tooth plate 5–7% HL; both plates touching or not. Minimal caudal peduncle depth 11.5–13% SL. Dorsal fin with one rudimentary and one long spine, and 7 branched rays. Pectoral fin with spine and 8–10 branched rays, pelvic fin with 6 rays (5 branched), anal fin with 9–13 rays.

Colouration

Adults often uniformly brownish. Pigmentation degree variable, on average lighter than in A. occidentalis . Pattern, if present, consisting of darker spots, often in rows on the flanks, sometimes confluent in (marbled) juveniles, more rarely consisting of larger reticulate spots. Fins often with (smaller) dots.

Maximum size recorded

540 mm SL.

Distribution

West African rivers from Senegal to Chad basins, and more east in the Nile and Lake Turkana basins ( Figure 9 ). Appears nowhere to be very numerous.

Figures

Figure 1. (A) Plot of principal components two and three (with percentage of total variance) of 31 log-transformed biometric data for 168 Auchenoglanis specimens; (B) plot of principal components two and three of 27 log-transformed biometric data for 168 Auchenoglanis specimens (all three barbel lengths, and combined premaxillary tooth plate width omitted); (C) ratio of postorbital to preorbital head length plotted against head length (measured until end of supraoccipital process) for 169 Auchenoglanis specimens. Type specimens are indicated by large symbols. For the A. biscutatus group: black circle: A. biscutatus holotype; grey circles: A. senegali types. For the A. occidentalis group: black triangle: A. occidentalis holotype; white triangles: A. o. tanganicanus types; white inverted triangles: A. acuticeps types; grey triangles: A. o. tchadiensis types; grey inverted triangles: A. wittei types. The Oxyglanis sacchii holotype is not included because its bad, dried state compromised many measurements.

Figure 8. (A) Holotype of Auchenoglanis biscutatus (MNHN 8969). (B) Holotype of Auchenoglanis occidentalis (MNHN 8971). Scale bars are 5 cm.

Figure 9. Confirmed localities of Auchenoglanis biscutatus and Auchenoglanis occidentalis. Symbols may represent multiple sampling locations. Locality of A. biscutatus holotype not exact (known locality: “Nile”).