Auchenoglanis acuticeps Pappenheim, 1914

Retzer, Michael E., 2010, Taxonomy of Auchenoglanis Günther 1865 (Siluriformes: Auchenoglanididae), Zootaxa 2655 (1), pp. 25-51 : 29-31

Auchenoglanis acuticeps Pappenheim, 1914

( Figs. 3a , 4 , 5b ; Table 2)

Auchenoglanis acuticeps Pappenheim, 1914:249 . Type locality: Lake Albert. Syntypes: ZMB 19094 (1), ZMB 21317 (3). In the original description, seven syntypes are listed. Presumably three specimens are missing or lost. Teugels, et al. 1991: 511 junior synonym of Auchenoglanis occidentalis (Valenciennes, 1840) .

Material examined: Country and Province unknown: Albert See, ZMB 19094, 1 , (169.7 mm SL, syntype) and ZMB 21317, 3 , (46.4–59.1 mm SL, syntypes). Democratic Republic of Congo, North Kivu: Lake Albert, FMNH 62948 , 1 , (496.0 mm SL); Lake Albert, Kasenyi , MRAC P–20871, 1, (240.0 mm SL) and MRAC P– 44937, 1, (290.0 mm SL). Egypt, Al-Wadi al Jadid: Lake Nasser , MRAC P–112 84-06, 1, (367.4 mm SL) and MRAC 83–30 –P–95–96, 2, (334.7–360.9 mm SL). Ethiopia, Gambella: Alwero River , CU 94645, 1, (237 mm SL). Sudan, Bahr el Gabel: White Nile River, Gemmeiza, AMNH 9822 , 1 , (280.9 mm SL). Jonglei: Awai River , BMNH 1984.9 .27.205, 1, (300 mm SL). Province unknown: Nile River , Kosheh, Nubia, BMNH 1907 . 12.2.2189 –2190, 2, (117.8–143.6 mm SL); Atbara River , USNM 52128 , 1 , (195.6 mm SL). Upper Nile: Nile River , Kodok, USNM 061288 , 2 , (114.8–163.4 mm SL) .

Diagnosis: Auchenoglanis acuticeps can be distinguished from all other Auchenoglanis , except A. sacchii (the pigmentation of A. sacchii is only vaguely known from its original description) by the presence of small round spots in a regular pattern on the body ( Fig. 5b ), adipose fin, caudal and dorsal fins. Other species of Auchenoglanis lack small round spots in a regular pattern on the body, adipose fin, caudal and dorsal fins.

Auchenoglanis acuticeps can be distinguished from A. sacchii and A. biscutatus by having a longer preorbitalhead length relative to the interorbital distance (PrOL to IOD ratio 1.5–1.9 in A. acuticeps versus 1.3 in A. sacchii and 0.9–1.4 in A. biscutatus ). Auchenoglanis acuticeps can be further distinguished from A. biscutatus by having the anterior margins of the nuchal plates straight to slightly curved rather than strongly curved ( Fig. 1a ). Auchenoglanis acuticeps can be further distinguished from A. wittei by having a shorter maxillary barbel length relative to the head length (MxBL to HL ratio in A. acuticeps 0.28–0.51 versus greater than 0.52 in A. wittei ). Auchenoglanis acuticeps can be further distinguished from 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. acuticeps versus over it in A. sacchii . Auchenoglanis acuticeps can be further distinguished from A. tchadiensis and A. occidentalis by its black maxillary barbels and grey-brown external and internal mandibular barbels versus all white to slightly brown barbels in A. tchadiensis and white external and internal mandibular barbels in A. occidentalis . The oblong-oval premaxillary tooth patches ( Fig. 2a ) of A. acuticeps further separates it from the round, triangular, square or tear-shaped tooth patches of A. biscutatus , A. tchadiensis , A. wittei , A. sacchii , A. tanganicanus and A. senegali .

Description: Morphometrics are presented in Table 2. The fin ray counts are as follows: dorsal fin II,7 (19); pectoral fin I,8 (8), I,9 (11); pelvic fin i,5 (17). The head is large with the dorsal edge in the lateral profile rising steeply from the tip of the snout to the dorsal-fin origin; the ventral edge is straight from the tip of snout to the lower posterior margin of the opercle. The body depth is greatest at the dorsal-fin origin. The dorsal 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 notches the rear edge of the supraoccipital.

The middle rays of the dorsal fin extend well 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 of the pelvic fin being the longest ray. The rays of the anal fin are much longer than its base, and the second or third branched ray is longest. The distal edge of the caudal fin is round to weakly emarginated.

The pectoral fin is placed approximately on the anterior one-third of the body, ahead of the dorsal-fin 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 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 thick.

The mouth is subterminal and narrow relative to the head width. The premaxillary tooth patches are oblong-oval 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 upper body has a regular pattern of dark spots that may become vague dorsally. The type specimens are juveniles and are faded badly, but they show that in small individuals the spots are large relative to those in large individuals. The spots may also be vague in the rayed and adipose fins and not at all apparent on the paired and anal fins that are otherwise brown or black. The caudal fin may be dark or with spots smaller than those on the body. On small individuals, the dark spots on the dorsal and caudal fins coalesce to form bands. The maxillary barbel is black, and the other barbels are white at the apex but may have some grey pigment distally. The upper lip is dark; lower lip is lightly pigmented. The sides and top of the head are dark and without spots. The lower side of the head is white with flecks of dark pigmentation.

Range: Auchenoglanis acuticeps is distributed from Lake Albert to the lower Nile ( Fig. 4 ). The species does not appear to occur in the Blue Nile.

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 4. Collection localities of Auchenoglanis acuticeps (black squares), A. biscutatus (black triangles), A. sacchii (open circle), and A. tchadiensis (black circles). Symbols may represent multiple collections.

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.