(Fig. 9)
Synonymy. Doumea typica , non Sauvage: Boulenger, 1911, in part, specimens from Cameroon; Hubbs, 1921, 3; Harry 1953, 219, fig.6, 11e,f.
Diagnosis. Of the species from WCA D. gracila is most and closely similar to D. typica but differs in proportions of caudal peduncle; caudal peduncle length 2.9-3.2 times in SL, (3-4 times in SL for D. typica ) caudal peduncle length 12.4-16.9 times depth (8-12 times for D. typica ); and in having smaller, wider spaced eyes. D. gracila is distinguished from D. thysi in the proportions of the caudal peduncle (caudal peduncle length 2.9-3.2 times in SL vs.more than 4.5 times for D. thysi ). It also differs in coloration from that species (dark brown or blackish with light saddles vs. brown with light stripe along lateral line for D. thysi ). It differs from D. sanagasp. nov. in the length of the caudal peduncle ( D. gracila caudal in SL 2.9-3.2 vs. 3.4-3.6 D. sanaga ) and in position of the dorsal fin: D. sanaga the dorsal fin is displaced further posteriorly so that there is a distinct ‘gap’ between the supraoccipital process and the nuchal shield of the dorsal fin, the spine of the nuchal shield meets with at least the second vertebrae behind the Weberian complex (in D. gracila and D. typica the gap is narrow and the spine of the nuchal shield intercepts the first vertebrae behind the Weberian complex). As far as is known D. gracila (max. SL 141 mm) is considerably larger than either D. thysi (max. SL 65.5 mm) or D. sanaga (max. SL 80 mm). Doumea alula Nichols & Griscom , a species from the Congo River basin, has a shorter, deeper caudal peduncle.
Description. Proportional measures and fin ray counts are given in Table 7. Body firm, slender, depressed anteriorly, strongly tapered to caudal base; bony ridge behind dorsal fin to adipose fin; thin mid-dorsal, midventral and bi-latero-ventral bony ridges along caudal peduncle. Head slender and pointed, 5.4-6.2 times in SL, flat below, smooth and rounded above, snout long 2/3 head length, nares in mid snout, slightly nearer to eyes than to anterior tip; mouth small, oval shaped, subterminal to ventral in position, lips above fleshy, papillose, lower lips divided by firm triangular pad; teeth not detected on premaxillary toothpad or median pad on mandible; barbels short, tapered and papillose, maxillaries extend from lateral edge of upper lip, not reaching to below orbits; outer pair of mandibular barbels extend from lateral corner of mouth, reach about 2/3 distance to edge of branchiostegal membrane, inner mandibular barbels extend from edge of mandibular toothpad, postero-medially to lateral pair, short, less than half the distance to the edge of the branchiostegal membrane; eyes small, on posterior third of head, widely separated (interorbit 1.7-2.4 times orbit diameter), orbits bony above; supraoccipital process slender, about half length of snout, nearly reaching nuchal shield; humeral process short, obscured. Branchiostegal membrane united, straight or slightly concave edge, covered with radiating unculi. Predorsal length one third of SL. Caudal peduncle long (length 2.9-3.6 times in SL), slender (length 9.3-16.9 times depth), depressed. Fins large, pointed and falcate; origin of dorsal less than one head length behind head; dorsal fin pointed, leading ray slender and stiff, hind edge straight to shallow concave in larger adults; pectoral fins large, falcate, not reaching base of pelvic fins, leading ray curved, pectinate, padded, outer rays lie horizontal, inner rays inclined dorsally; origin of pelvic fins behind base of dorsal fin, pelvic fins falcate, reaching beyond origin of anal fin base, leading ray curved, pectinate and padded; anal fin with straight hind edge, not reaching caudal fin base; caudal with compact base, deeply forked with pointed lobes, ventral lobe longer than dorsal; adipose fin short, triangular, placed over posterior anal base. Ano-genital openings placed about midway between pelvic and anal fin base, males with short conical genital papillae. Lateral line visible as thin white line in preserved specimens, complete to base of caudal, with short branches to pores above and below main stem. Reaches 141 mm SL.
Coloration. Countershaded, dark grey to black or brown above, light creamy brown below from snout to anal fin, some sooty pigment to caudal; boundary between dorsal and ventral sections sharply demarcated along body below lateral line, dark patches above pelvic bases, 3-6 light patches or saddles on dorsal surface from behind head to caudal, head above dark grey, black or brown with light brown patches over gill covers and behind eyes, dark pre-orbital stripes sometimes evident. Fins with grey-black rays, paired fins grey-black above with light medial section, outer rays of caudal dark grey-black. Lateral line a thin white branched line along mid-flanks.
Distribution. Nyong to Ntem Rivers, in southern Cameroon (Fig. 10).
Etymology. From Latin ‘gracilus’ meaning graceful and slender. A noun in apposition.
Doumea gracila[1][2] is a species of catfish in the genus Doumea. It lives from Nyong to the Ntem rivers in southern Cameroon.[3][4]
Doumea gracila is a species of catfish in the genus Doumea. It lives from Nyong to the Ntem rivers in southern Cameroon.
