Amphilius lujani Thomson & Page

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 : 81-84

Amphilius lujani Thomson & Page , new species

( Fig. 9 , Tables 7 )

Amphilius jacksonii .— Seegers et al., 2003: 37, Lake Victoria drainage (affluent rivers) [Nile basin]

Holotype. UF 184238, ex. UF 169233, Uganda, Manafwa River at Bumwangu, Lake Kyogo drainage, Nile basin, 00°56'26.2”N, 34°16'49.2"E (104.1 mm SL).

Paratypes. Lake Kyogo drainage: AUM 47147, same data as holotype (16: 37.7–112.3); AUM 47149, Uganda, Malaba River at Lwakhakha, border between Uganda and Kenya, 00°47'04”N, 34°22'44"E (7: 46.3–98.1); BMNH 1961.6.13.19, Uganda, Malawa [=Malaba] River, ca. 00°35'N, 34°03'E (1: 99.4); BMNH 1962.2.6.62–63, Uganda, Malawa [=Malaba] River, ca. 00°35'N, 34°03'E (2: 80.0–107.9); BMNH 1965.10.15.18–21, Kenya, Malikisi River, ca. 01°37'N, 34°13'E (4: 35.7–48.0); CU 97333, same data as holotype, ex. AUM 47147 (3: 50.3– 90.5); MRAC B3–06–P–17–19, same data as holotype, ex. UF 169233 (3: 56.0–88.1); SAIAB 187280, same data as holotype, ex. UF 169233 (3: 47.9–98.0); UF 169233, same data as holotype (15: 43.0–107.6); UF 169235, same data as AUM 47149 (7: 45.4–90.1).

Non-types. Lake Kyogo drainage: BMNH 1965.10.15.11–13, Uganda, Sironko River, ca. 01°29'N, 34°14'E (2: 103.7–119.5); BMNH 1965.10.15.14–15, Uganda, Sironko River, ca. 01°29'N, 34°14'E (1: 101.1); BMNH 1965.10.15.16–17, Uganda, Zuzu River, tributary of the Manafwa River, ca. 01°13'N, 34°21'E (2: 40.9–42.1). Lake Manyara basin: BMNH 1969.2.20.1, Tanzania, Stream entering Lake Manyara, ca. 03°38'S, 35°41'E (1: 45.0). Nzoia River system (NE Lake Victoria tributary): SAIAB 65048, Kenya, Moi Brgidge, Little Nzoia River, ca. 00°55'N, 35°07'E (1: 74.5).

Diagnosis. Diagnostic characters are summarized in Table 2 . Amphilius lujani is diagnosed from A. pedunculus , A. frieli , and A. crassus by having a more slender caudal peduncle (depth 8.1–9.5% SL vs. 9.9–12.3% SL). It is diagnosed from A. jacksonii by having a deeper caudal peduncle (depth 8.1–9.5% SL vs. 4.8–7.9% SL) and a deeper body (body depth at anus 13.5–15.8% SL vs. 9.6–13.2% SL). Amphilius lujani is diagnosed from A. ruziziensis by having a wider interorbital width (28.3–31.7% HL vs. 23.4–25.1% HL) and a deeper body (body depth at anus 13.5–15.8% SL vs. 11.1–12.9% SL). It is further diagnosed from A. frieli by having fewer gill rakers on the first gill arch (6–8, rarely 5 or 9 vs. 10–11, rarely 9 or 12) and a longer caudal peduncle (length 16.8–20.9% SL vs. 14.4–16.4% SL). Amphilius lujani is further diagnosed from A. crassus by having more branched pectoralfin rays (9 vs. 7–8, rarely 9) and a longer caudal peduncle (length 16.8–20.9% SL vs. 13.3–15.5% SL).

Description. Morphometric data are in Table 7 . 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 dorsal-fin origin, 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 openings located at midpoint of adpressed pelvic fin, closer to pelvic-fin insertionthan 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 V -shaped connection.

Mouth broad, gently curved, subterminal. Lips moderately fleshy, strongly papillate. Rictal lobe large and papillate. Anterior portion of premaxillary tooth band exposed with mouth closed. Premaxillary tooth patches joined, forming crescent shaped band. 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 origin of pectoral-fin. Inner mandibular barbel originates anterolaterally of inner mandibular barbel, extending to edge of branchiostegal membrane. Branchiostegal membrane with 7 (21), or 8 (25) rays. Gill rakers on first epibranchial 2 (36) or 3 (10); rakers on first ceratobranchial 4 (2), 5 (22), 6 (1), or 7 (1); total gill rakers on first arch 6 (2), 7 (16) 8 (23) or 9 (5).

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 pectoral fin. Dorsal fin with i,6 (45) or i,7 (1) rays, and fin margin straight. Pectoral fin with i,9 (46) 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 of dorsal-fin insertion. Pelvic fin with i,5 (46) 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, deeply incised posteriorly. Caudal fin deeply forked with tips of lobes rounded; fin with i,5,6,i (46) principal rays. Anal fin with short base, origin posterior to origin of adipose-fin base, with ii,6 (10), ii,7 (12), iii,6 (19), or iii,7 (6) rays. Anal-fin margin almost straight.

Coloration. Body variably mottled with dark saddles. First saddle posterior of head, second saddle at 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 faint medial bands. Adipose fin dark brown to black, with posterior distal edge cream-colored. Pectoral and pelvic fins positioned horizontally with upper surfaces cream-colored with darkened fin base and faint medial bands. Lower surfaces light yellow. Caudal fin cream-colored with dark markings on upper and lower lobes. Caudal coloration asymmetrical, with lower lobe almost completely dark (except for small cream-colored mark at base of caudal and cream-colored tip). Upper lobe with less dark pigment, with dark blotch covering dorsal edge, but caudal base with large cream-colored patch and tip cream-colored.

Distribution. Lake Kyogo drainage, western Uganda; Nzoia River, a northeastern tributary of Lake Victoria, and Lake Manyara basin, Tanzania ( Fig. 6 ).

Etymology. Named for Nathan K. Lujan who collected the holotype and most paratypes of this species, and who has made excellent contributions to our knowledge of freshwater fishes.

Figures

FIGURE 6. Distributions of Amphilius pedunculus (diamonds), A. frieli (dots), A. crassus (crosses) and A. lujani (squares).

FIGURE 9. Amphilius lujani, UF 184238, 104.1 mm SL, holotype; lateral, dorsal and ventral views.

Tables

TABLE 7. Morphometric data for Amphilius lujani. Range and mean include the holotype.

	Holotype	Range (n=45)	Mean±SD
%SL
Head length	24.2	22.4–25.0	24.1±1.3
Head width	19.5	19.1–20.7	19.5±0.9
Head height	13.3	11.7–14.3	13.2±1.3
Body depth	16.7	14.4–18.5	16.7±2.1
Body depth at anus	15.6	13.5–15.8	14.3±1.2
Predorsal length	36.0	34.4–38.3	36.5±2.0
Prepectoral length	18.9	17.6–20.5	19.2±1.5
Preanal length	72.9	69.0–74.4	71.5±2.7
Dorsal-fin base length	11.4	10.3–13.3	11.5±1.5
Adipose-fin base length	22.5	18.1–23.1	20.3±2.5
Anal-fin base length	12.2	10.3–14.0	11.8±1.8
Pelvic-fin length	17.8	17.5–21.5	19.2±2.0
Pectoral-fin length	21.8	20.0–23.6	22.3±1.8
Anal-fin length	16.8	16.8–20.9	18.8±2.1
Caudal-peduncle length	17.1	16.8–20.9	18.1±2.1
Caudal-peduncle depth	9.6	8.1–9.5	8.9±07
Anus to anal fin length	15.1	11.8–16.2	14.4±2.2
Prepelvic length	50.1	46.5–50.3	48.6±1.9
Postpelvic length	51.8	49.3–56.2	52.1±3.5
Dorsal-fin insertion to adipose	41.8	38.2–42.0	40.6±1.9
Dorsal-fin origin to caudal	66.2	65.3–69.0	66.8±1.9
Preanus length	58.7	54.8–60.6	57.2±2.9
%HL
Snout length	50.5	42.9–52.9	49.5±5.1
Interorbital distance	28.7	28.3–31.7	29.2±1.8
Maxillary barbel length	83.3	61.6–85.0	73.2±11.7
Inner mandibular barbel length	38.7	35.1–44.6	40.6±4.8
Outer mandibular barbel length	61.9	48.2–72.4	61.9±12.2
Eye diameter	13.8	12.6–18.0	15.2±2.7