Auchenoglanis wittei Giltay, 1930

Retzer, Michael E., 2010, Taxonomy of Auchenoglanis Günther 1865 (Siluriformes: Auchenoglanididae), Zootaxa 2655 (1), pp. 25-51 : 34-37

Auchenoglanis wittei Giltay, 1930

( Figs. 3b , 5a , 6 ; Table 2)

Auchenoglanis Wittei Giltay, 1930: 92 . Type locality: Stanleyville (now Kinsangani). Holotype: MRAC P–19802, Cotypes: IRSNB 35 (1), MRAC P–9802 (1). Teugels, et al. 1991, 511: junior synonym of Auchenoglanis occidentalis (Valenciennes, 1840) .

Material examined: Democratic Republic of Congo, Equateur: Lake Tumba, MRAC P–57745, 1, (218.0 mm SL); Tshuapa River, near Boende , MRAC P–73023.5164, 1, (224.0 mm SL); tributary , Congo River, near Bumba , MRAC P–88025–1656, 1, (106.0 mm SL) . Maniema: Lualaba River, Kindu , MRAC P–70095, 1, (143.1 mm SL) and MRAC P–70094, 1, (139.0 mm SL) . Orientale: Lualaba River, AMNH 6992 , 1 , (118.4 mm SL), Buta, MRAC P–61597, 1, (144.0 mm SL), Stanleyville ; MRAC P–19802, 1, (47.9 mm SL, holotype) and MRAC P–19803, 1, (42.8 mm SL, cotype); Isalowe River , Yangambi , MRAC P–123541, 1, (175.0 mm SL). Sud Kivu: Ulindi River , MRAC P–75191, 1, (237.0 mm SL) .

Diagnosis: Auchenoglanis wittei can be distinguished from all other Auchenoglanis except A. sacchii (the pigmentation of A. sacchii is only vaguely known from its original description) by its pigmentation of medium irregular-shaped spots in a reticulated pattern on the body of adults ( Fig. 5a ). The spots on the body become faint on large adults. These spots are also present on the dorsal, caudal, and adipose fins but faint or absent on the paired fins and anal fin. Other species of Auchenoglanis lack medium spots in a reticulated pattern on the body and adipose, caudal, and dorsal fins.

Auchenoglanis wittei can be distinguished from A. biscutatus by having the anterior margins of the nuchal plates straight to slightly curved rather than strongly curved ( Fig. 1a ) and from A. sacchii and A. biscutatus by having a longer preorbital-head length relative to interorbital distance (PrOL to IOD ratio 1.7–1.9 in A. wittei versus 1.3 in A. sacchii and 1.4 in A. biscutatus ). Auchenoglanis wittei can be further distinguished from A. senegali , A. occidentalis , and A. acuticeps by having a longer maxillary barbel length relative to the head length (MxBL to HL ratio 0.53–0.68 in A. wittei versus less than 0.53 in A. senegali , A. occidentalis , and A. acuticeps ). In addition, A. wittei can be further distinguished from A. senegali and A. occidentalis by having a longer maxillary barbel length relative to the preorbital-head length (MxBL to PrOL ratio 0.9–1.2 in A. wittei versus less than 0.9 in A. senegali and A. occidentalis ).

Adults of A. wittei can be distinguished from adult A. biscutatus and A. senegali by having the anterior edge of the adipose fin that rises gradually to its maximum height at the posterior end of the fin, well behind the mid-point of the adipose fin versus the anterior edge of the fin that rises steeply and reaches its maximum height at a point approximately one half of the length of the adipose fin. The origin of the adipose fin is before the anal-fin origin in A. wittei versus over it in A. sacchii . Auchenoglanis wittei can be further distinguished from the other Auchenoglanis species except A. biscutatus and A. tanganicanus by its black maxillary, external and internal mandibular barbels versus not all barbels being black. The squarish premaxillary tooth patches ( Fig. 2c ) of A. wittei further separates it from the oblong-oval, round, triangular, or tear-shaped tooth patches of A. occidentalis , A. acuticeps , A. biscutatus , A. tchadiensis , and A. senegali .

Description: Morphometrics are presented in Table 2. The fin ray counts are as follows: dorsal fin II,7 (N=11); pectoral fin I,6 (1), I,8 (3), I,9 (5), I,10 (1); pelvic fin i,5 (2), i,6 (1). The head is large with the dorsal edge in the lateral profile rising steeply from the tip of the snout to the orbit then less steeply to the dorsal-fin origin; the ventral edge is concave from tip of snout to the lower posterior margin of the opercle. Body depth is greatest at the dorsal-fin origin. The dorsal-lateral profile descends less steeply from the dorsal-fin origin to the caudal peduncle. The minimum caudal-peduncle height is at the posterior end of the base of the adipose fin. The ventral-lateral profile from the rear of the head to the anal fin is flat and concave at the caudal peduncle. In adults the leading lateral edges of the nuchal plates are straight or slightly curved. The leading lateral edges converge to form a point at the anterior end of the first nuchal plate and that plate sometimes notches the rear margin of the supraoccipital. Note that the type specimens examined are very small nonadults and in these specimens the anterior end of the first nuchal plate is pointed and the distal edge of the supraoccipital is distinctly notched by the point of the nuchal plate.

The middle rays of the dorsal fin extend somewhat beyond the spine and the first and last rays. The dorsal spine is stout and nonserrated on the posterior edge. The pectoral fin is pointed with the first rays much longer than the last rays. The distal edge of the pectoral fin is straight to slightly convex. The pectoral spine is stout and serrated on the posterior edge. The distal edge of the pelvic fin is convex with the second branched ray being the longest ray. The rays of the anal fin are much longer than its base, and the second or third branched ray of the anal fin is longest. The distal edge of the caudal fin is round to weakly emarginated.

The pectoral fin is placed approximately on the anterior one quarter of the body, well ahead of the dorsalfin origin. The pelvic fin is placed behind the dorsal-fin origin. The anal fin is placed approximately on the posterior one third of the body.

The maxillary barbel is approximately three quarters of, to equal to, the length of the external mandibular barbel. The internal mandibular barbel is much shorter than the other barbels. The maxillary and external mandibular barbels are slender, but the internal mandibular barbel is thicker particularly at the base. The lower lip is thin.

The mouth is subterminal and narrow relative to the head width. The premaxillary tooth patches are square in shape.

The color is based on examination of specimens preserved in alcohol. The adult body is dark dorsally and laterally but light ventrally. The body has a regular pattern of dark spots in a reticulated pattern that may become vague dorsally. In some adults, two or three very dark spots are present in a line just above the lateral line. The dark spots are present in the dorsal, caudal, and adipose fins. They are less visible in the anal fin and paired fins that are otherwise brown. On small individuals, the reticulate pattern is more apparent with the spots in the dorsal and caudal fins coalescing to form bands and spots evident in all of the fins. The barbels are mostly black although the base of the external and internal mandibular barbels may be less pigmented. The upper lip is dark; lower lip is lightly pigmented. The sides and top of the head are brown and without spots. The lower side of the head is white.

Range: Auchenoglanis wittei is found in the central Congo Basin ( Fig. 6 ).

Figures

FIGURE 1. Diagrams of nuchal plate patterns of Auchenoglanis. a) leading edge straight, b) leading edge curved. The arrow indicates the anterior end of the plates. The numbers indicate individual plates.

FIGURE 2. Diagrams of the five types of premaxillary tooth patches of Auchenoglanis. a) oblong-oval, b) round, c) square, d) tear, and e) triangle. The arrow indicates the direction of the anterior end of the patches.

FIGURE 3. Lateral views of a) Auchenoglanis acuticeps CU 94645, 237.0 mm SL, b) A. wittei MRAC P–57745, 218.0 mm SL, and c) A. tanganicanus SAIAB 56692, 237.7 mm SL.

FIGURE 5. Pigmentation patterns of the lower side of the body above the pelvic fin of a) A. wittei (MRAC P–123541) and b) A. acuticeps (CU 94645). Anterior is to the left.

FIGURE 6. Collection localities of Auchenoglanis tanganicanus (black circles) and A. wittei (black squares). Symbols may represent multiple collections.