Amphilius jacksonii Boulenger 1912

Thomson, Alfred W., Page, Lawrence M. & Hilber, Samantha A., 2015, Revision of the Amphilius jacksonii complex (Siluriformes: Amphiliidae), with the descriptions of five new species, Zootaxa 3986 (1), pp. 61-87 : 63-67

Amphilius jacksonii Boulenger 1912

( Fig. 2 , Table 1 )

Amphilius jacksonii Boulenger 1912: 602 , Original description, Type locality: Hima R. flowing into Lake George (Ruisamba), eastern Uganda, elev. 3500 ft. [Lake George drainage, Nile basin], holotype: BMNH 1912.10.15.47; Boulenger, 1916: 307, fig. 182, description based on type; David & Poll, 1937: 255, description, Rutshuru River [Lake Edward drainage, Nile basin]; Poll, 1939: 17, 62, records from Albert National Park [Lake George and Lake Edwards drainages]; Harry, 1953: 190, synonymy; Greenwood, 1957: 77, figs. 49, 80, description, size, habitat, distribution [Lake George and Lake Edwards drainages]; Copely, 1958: 154, Hima R.; Greenwood, 1958: 89, fig. 49, description, size, habitat, distribution [Lake George and Lake Edwards drainages]; Whitehead, 1958: 198, western Uganda rivers; Corbet, 1961: 81 [not examined]; Greenwood, 1966: 93, fig. 49, description, size, habitat, distribution [Lake George and Lake Edwards drainages]; Seegers, 1996a: 188, figs. 133–134 (in part), type information, holotype figured, Seegers, 1996b: 251 (in part), type information, distribution; Walsh et al., 2000: 166, redescription, diagnosis, description, life-history aspects, habitat, distribution [Lake George drainage].

Material examined. Lake George drainage: AMNH 97419, Uganda, Dura River, Dura station, south end of Kibale Forest Reserve near Queen Elizabeth National Park, ca. 0°12'00”N, 30°22'00"E (6: 41.9–79.5); BMNH 1912.10.15.47, Uganda, Hima River, ca. 0°17'19”N, 30°10'23"E (1: 86.7, holotype); BMNH 1971.1.5.37–38, Uganda, Mapanga River, about 8 km upstream just below rapids, ca. 0°05'10.6”N, 30°23'03.8"E (2: 58.7–60.1); BMNH 1971.1.5.39, Uganda, Sibwe River, ca. 0°10'01.4”N, 30°12'36.8"E (1: 87.0); BMNH 1971.2.19.14–15, Uganda, Sibwe River, ca. 0°10'01.4”N, 30°12'36.8"E (1: 87.0); CU 97331, ex. UF 110746 (4: 37.6–92.7); MCZ 100587, Uganda, Middle Dura River, Kanyanchu, Kibale Forest Reserve, ca. 0°27'00”N, 30°22'00"E (1: 76.7); MRAC 90–046–P–68–78, Uganda, Ruimi (Rwimi) River, road between Fort Portal-Kasese [Route A 109], ca. 0°22'23.5”N, 30°12'40.8"E (11: 44.0–84.2); MRAC 90–046–P–79–87, Uganda, Ruimi (Rwimi) River, road between Fort Portal-Kasese [Route A 109], ca. 0°22'23.5”N, 30°12'40.8"E (11: 47.2–83.0); SAIAB 187245, ex. UF 110746 (42.3–97.0); UF 110743, Uganda, Middle Dura River, Kanyanchu, Kibale Forest Reserve, ca. 0°27'00”N, 30°22'00"E (12: 48.6–104.3); UF 110744, Uganda, Middle Dura River, Kanyanchu, Kibale Forest Reserve, ca. 0°27'00”N, 30°22'00"E (19: 23.6–115.9); UF 110745, Uganda, Middle Dura River, Kanyanchu, Kibale Forest Reserve, ca. 0°27'00”N, 30°22'00"E (5: 54.6–88.6); UF 110746, Uganda, Middle Dura River, Kanyanchu, Kibale Forest Reserve, ca. 0°27'00”N, 30°22'00"E (36: 34.1–102.0); UF 110747, Uganda, Dura River-Mainaro, ca. 0°37'00”N, 30°16'00"E (34: 54.4–111.1); UF 110748, Uganda, Ruimi River at bridge on road between Fort Portal and Hima, ca. 0°22'22.2”N, 30°12'41"E (41: 42.7–92.8); UF 110749, Uganda, Ruimi River at bridge on road between Fort Portal and Hima, ca. 0°22'22.2”N, 30°12'41"E (1: 47.6); UF 110750, Uganda, Mubuku River at bridge on road between Fort Portal and Kasese, ca. 0°15'30.8”N, 30°07'9.7"E (7: 52.8–85.1). Lake Edward drainage: AUM 47138, Uganda, Munyage River, below Butogota town, DRC-Uganda border foot path, elev. 1190m, 0°53'00”S, 29°37'50"E (3: 60.1–69.9); AUM 47139, Uganda, Tributary of Ishasha at bridge between Karangara and Butogota. Outside BINP, sources in park, elev. 1180m, 0°52'18”S, 29°39'59"E (2: 73.41–80.8); AUM 47143, Uganda, River Ishash, below bridge in cattle farm on Butogota-Kanungu road. elev. 1300m, 0°49'50”S, 29°38'21"E (2: 65.7–73.4); AUM 47146, Uganda, Bwindi Impenetrable Forest National Park, ca. 0°1'26”S, 29°41'23"E (4: 58.8–86.6); MRAC 22551, Uganda, Rutshuru, Buseregenyi, ca. 1°04'00”S, 29°26'00"E (1: 80.0); MRAC 23233, Uganda, Rutshuru, Buseregenyi, ca. 1°04'00”S, 29°26' 00"E (1: 82.2); MRAC A5–019– P–0048–0056, Uganda, Munyage River, below Butogota town, DRC-Uganda border foot path, elev. 1190m, ca. 1°04'00”S, 29°26'00"E (9: 39.4–97.3); UF 169241, ex. AUM 47143 (3: 65.9–70.7); UF 169242, ex. AUM 47139 (3: 80.7–87.3); UF 169243, ex. AUM 47138 (2: 67.1–86.3); UF 169257, ex. AUM 47146 (3: 60.7–75.1). Kagera River drainage: MRAC 164876, Rwanda, Mwogo River, 18 km NE of Butare, ca. 2°29'00”S, 29°38'00"E (1: 77.2); MRAC 71783–850, Rwanda, Mwogo River, the source of the Nile, ss-tributary of Kagera River, ca. 2°22'52”S, 29°41'48"E (61: 38.5–107.0); MRAC 71851–925, Rwanda, Mwogo River, the source of the Nile, sstributary of Kagera River, ca. 2°22'52”S, 29°41'48"E (74: 38.5–106.4); MRAC 83417, Burundi, Urigoli, Nyalugogo [Nyabugogo?] River, Urigoli territory, ca. 3°25'26”S, 29°53'30"E (1: 34.7); MRAC 86–27–P–0088– 0 0 95, Rwanda, Rubondo River, tributary of Kiryango River, near town of Mukugi, ca. 2°12'00”S, 29°41'00"E (8: 51.8–86.1); MRAC 91–30–P–0296–0299, Burundi, Nyakijanda River, tributary of Ruvubu River, the bridge on Road of General Interest 4, 38 km from Kinyinya, ca. 3°36'00”S, 30°07'00"E (4: 49.5–65.0); MRAC 91–34–P– 0147–0150, Burundi, Kavuruga River, tributary of Ruvubu River, near town of Buhinyuza, ca. 3°02'00”S, 30°21'00"E (4: 49.4–74.9); MRAC 91–34–P–0151–0152, Burundi, Kinyanderama River, tributary of Ruvubu River, near town Buhinyuza, ca. 3°02'00”S, 30°21'00"E (2: 66.6–71.1); MRAC 91–34–P–0160–0164, Burundi, Nyabiko River, on Muyinga-Gitega road, small tributary, rocky and sandy bottom, ca. 5°29'00”S, 30°14'00"E (5: 35.1–92.3); MRAC 91757–763, Rwanda, Nyabugogo River at confluence of Lusine River, ca. 1°47'41”S, 30°07'23"E (7: 58.9–96.8); MRAC 91764–836, Rwanda, Nyabugogo River at confluence of Lusine River, ca. 1°47'41”S, 30°07'23"E (72: 34.9–79.8); MRAC 93097–120, Rwanda, Nyabugogo River, at outlet of Lake Mohasi, ca. 1°46'45”S, 30°07'58"E (23: 28.2–77.0); MRAC 94272–276, Rwanda, ca. 2°32'15”S, 29°40'16"E (5: 40.1– 82.9); MRAC 96031.1611–1614, Burundi, Karuzi, small tributary stream of the fish-farming ponds, Ndurumu system, ca. 3°06'05”S, 30°09'53"E (4: 29.3–78.4).

Diagnosis. Diagnostic characters are summarized in Table 2 . Amphilius jacksonii is diagnosed from all other species of the Amphilius jacksonii complex by its more slender caudal peduncle (4.8–7.9% vs. 8.1–12.3% SL). It is further distinguished from A. pedunculus , A. frieli , and A. crassus by its longer caudal peduncle (caudal-peduncle length 16.7–20.6 vs. 13.3–18.8% SL), and from A. frieli , A. crassus , and A. lujani by its more slender body (body depth at anus 9.6–13.2% vs. 13.5–17.4% SL). It is further distinguished from A. frieli by having fewer total gill rakers on the first gill arch (6–9, rarely 10 vs. 10–11, rarely 9 or 12) and from A. ruziziensis by having a wider interorbital width (26.7–32.0 HL vs. 23.4–25.1% HL).

Description. Morphometric data are in Table 1 . Body elongate, ventral profile flattened ventrally to anal-fin base, then tapered dorsally to end of caudal peduncle. Dorsal profile rising gently from tip of snout to origin of dorsal fin, then nearly horizontal to end of caudal peduncle. Greatest body depth at dorsal-fin origin. Caudal peduncle laterally compressed, with crenellated epidermal fold. Anus and urogenital opening located at midpoint of adpressed pelvic fin, closer to pelvic-fin insertion than to origin of anal fin. Skin smooth. Lateral line complete, extending from dorsal edge of opercular cavity to caudal-fin base.

Head and anterior part of body depressed and broad. Head wedge-shaped in lateral view. Snout broad, blunt when viewed from above. Head becoming wider from tip of snout to pectoral-fin base. Branchiostegal membranes moderately joined at isthmus forming a U -shaped connection.

Mouth broad, gently curved, subterminal. Lips moderately fleshy, slightly papillate. Rictal lobe large and papillate. Anterior portion of premaxillary tooth band exposed with mouth closed. Premaxillary tooth patches joined, forming V -shaped band with anterior broad protrusion. Premaxillary and dentary teeth short, conical. Dentary tooth patches forming U -shaped band, separated medially.

Three pairs of simple, tapered circumoral barbels. Maxillary barbel large, fleshy and flattened with pointed tip; barbel extending posterolaterally from corner of mouth to pectoral-fin base. Outer mandibular barbel thin with pointed tip, origin at posterior corner of lower jaw, extending to pectoral-fin origin. Inner mandibular barbel originates anterolaterally of inner mandibular barbel, extending to edge of branchiostegal membrane.

Branchiostegal membrane with 6 (5), 7 (85), 8 (147), or 9 (1) rays. Gill rakers on first epibranchial 1 (4), 2 (178) or 3 (47); rakers on first ceratobranchial 4 (22), 5 (88), 6 (99), 7 (15), or 8 (1); total gill rakers on first arch 6 (25), 7 (74), 8 (83), 9 (38), or 10 (6).

Eye small, positioned dorsolaterally approximately midway between tip of snout and posterior margin of operculum. Horizontal diameter of eye slightly wider than vertical diameter. Eye without free orbit, covered with skin confluent with dorsal surface of head. Anterior and posterior nares with prominent tubular rims; nares separate but relatively close to each other. Posterior nare located about midway between eye and tip of snout.

Dorsal-fin origin at point over tip of adpressed pectoral fin. Dorsal fin with i,6 (243) rays, margin straight. Pectoral fin with i,7 (1), i,8 (104), or i,9 (137) rays; unbranched ray greatly thickened. Pectoral fin with four or five innermost rays progressively shorter making posterior fin margin rounded. Origin of pelvic fin posterior to dorsalfin insertion. Pelvic fin with i,5 (243) rays with first ray unbranched and greatly thickened. Pelvic fin with straight posterior margin.

Adipose-fin base longer than anal-fin base, origin anterior to origin of anal-fin base; fin extending past anal-fin insertion. Margin strongly convex with sharply rounded edge, not deeply incised posteriorly. Caudal fin deeply forked with tips of lobes rounded; fin with i,5,5,i (8), i,5,6,i (230), or i,6,6,i (1) principal rays. Anal fin with short base, origin posterior to origin of adipose-fin base, with ii,6 (62), ii,7 (107), ii,8 (9), iii,6 (48), iii,7 (16), or iv7 (1) rays. Anal-fin margin almost straight.

Character Amphilius A. ruziziensis A. pedunculus A. frieli A. crassus A. lujani

jacksonii

Coloration. Body variably mottled and with dark saddles. First saddle immediately posterior of head, second saddle under dorsal fin, third saddle between dorsal and adipose fins, fourth saddle under anterior part of adipose fin, and fifth saddle on caudal peduncle. All saddles connected laterally by broad stripe. Venter light brown with fourth and fifth saddles meeting those of opposite side. Dorsal and anal fins light brown with dark medial band. Adipose fin dark brown, cream-colored distally. Pectoral and pelvic fins positioned horizontally with upper surfaces brown and lower surfaces light yellow, each with dark medial band. Caudal fin brown with medial cream patch and tips of upper and lower lobes cream. Caudal coloration asymmetrical, lower lobe with more pigment than upper lobe.

Distribution. Lake George, Lake Edwards, and Kagera River drainages, Nile basin, eastern Uganda, Rwanda, and Burundi ( Fig. 3 ).

Figures

FIGURE 2. Amphilius jacksonii, UF 110743, 90.3 mm SL; lateral, dorsal and ventral views.

FIGURE 3. Distributions of Amphilius jacksonii (dots) and A. ruziziensis (triangles).

Tables

TABLE 1. Morphometric data for Amphilius jacksonii. Range and mean include the holotype.

%SL	Holotype	Range (n=31)	Mean±SD
Head length Head width Head height Body depth Body depth at anus	22.2 18.2 11.8 13.0 11.5	21.2–26.6 18.1–21.7 11.5–14.0 11.5–17.0 9.6–12.0	24.0±1.3 19.4±1.0 12.5±0.8 14.4±1.3 11.3±0.7
Predorsal length Prepectoral length Preanal length Dorsal-fin base length Adipose-fin base length	37.7 18.5 73.1 9.8 –	31.7–39.8 17.4–22.7 67.8–77.4 8.5–13.4 18.2–25.9	36.2±1.5 19.5±1.4 71.2±2.0 10.8±1.2 21.7±2.1
Anal-fin base length Pelvic-fin length Pectoral-fin length Anal-fin length Caudal-peduncle length	10.6 19.3 22.8 15.6 18.6	10.2–18.0 17.9–23.6 19.7–27.7 13.7–22.5 16.7–20.1	12.0±1.5 20.5±1.3 23.6±1.8 19.3±1.9 18.7±0.8
Caudal-peduncle depth Anus to anal fin length Prepelvic length Postpelvic length Dorsal-fin insertion to adipose	7.3 17.3 50.5 49.7 –	4.8–7.9 11.8–17.9 43.9–50.9 47.0–56.2 40.6–43.7	7.1±0.6 14.5±1.5 48.4±1.7 52.4±2.2 42.2±0.9
Dorsal-fin origin to caudal Preanus length %HL Snout length Interorbital distance	– – 44.8 29.2	59.7–71.7 51.7–60.0 44.8–55.1 26.7–32.2	66.2±2.1 56.6±2.0 48.3±2.2 28.3±1.2
Maxillary barbel length Inner mandibular barbel length Outer mandibular barbel length Eye diameter	65.1 – – 15.6	64.8–90.2 34.1–47.2 49.8–73.1 13.4–19.2	75.5±6.5 40.8±3.1 62.2±6.1 16.5±1.4

TABLE 2. External traits diagnostic for species of the Amphilius jacksonii complex.

Branchiostegal rays Branched pectoral rays	7–8, rarely 6 or 9 8–9, rarely 7	6–7 8–9	7–8 8–10	8–9 9–10	6–7, rarely 8 7–8 7–8, rarely 9 9
Total gill rakers Gill rakers on first ceratobranchial Caudal-peduncle depth	6–9, rarely 10 4–7, rarely 8 4.8–7.9	6–8, rarely 5 or 9 4–6, rarely 3 or 7 8.6–9.5	7–9, rarely 6 or 10 5–6, rarely 4 or 7 9.9–12.3	10–11, rarely 9 or 12 7–8, rarely 6 or 9 9.7–11.4	6–8, rarely 9 6–8, rarely 5 or 9 4–6, rarely 3 5–6, rarely 4 or 7 10.1–12.0 8.1–9.5
Caudal-peduncle length Interorbital width Dorsal-fin insertion to adipose-fin insertion Body depth at anus	16.7–20.6 26.7–32.0 40.6–43.7 9.6–13.2	18.7–20.3 23.4–25.1 38.2–41.5 11.1–12.9	16.0–18.8 28.1–35.8 37.5–41.7 11.4–17.7	14.4–16.4 25.1–27.7 37.5–41.2 13.9–14.9	13.3–15.5 16.8–20.9 28.9–34.1 28.3–31.7 42.2–44.6 38.2–42.0 14.5–17.4 13.5–15.8