Amphilius pedunculus 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 : 70-75

Amphilius pedunculus Thomson & Page , new species

( Fig. 5 , Table 4 )

Amphilius jacksonii .—David, 1937: 418, Malagarasi River; De vos et al., 2001: 131, Malagarasi River.

Holotype. CU 97334, ex. CU 95207, Tanzania, Malagarasi River at Lower Igamba Falls (Kasagwe), Malagarasi River drainage, 5°10'48”S, 30°03'03"E (52.3 mm SL).

Paratypes. Malagarasi River drainage: CU 90414, Tanzania, downstream of bridge across Malagarasi River at Uvinza, 5°07'03.7”S, 30°22'27.1"E (1: 50.8); CU 95207, same data as holotype, (16: 41.3–69.8); CU 95208, Tanzania, Malagarasi River up river 12 km E of Uvinza near village of Kanzibwe, 5°08'23.5”S, 30° 29' 21.6"E (1: 55.3); CU 95209, Tanzania, Malagarasi River downriver 4 km W from Uvinza; village of Nkwasa, 5°05'52.6”S, 30°21'16.2"E (5: 38.1–74.7); CU 95210, Tanzania, Malagarasi River near fork in road to Ngutu, 5°06'56.3”S, 30°17'48.1"E (1: 67.6), CU 95211, Tanzania, Malagarasi River in first site in gorge, 5°13'44.2”S, 30°13'26.5"E (6: 41.2–52.9); CU 95212, Tanzania, Malagarasi River in gorge, 5°12'10.2”S, 30°10'11.1"E (1: 44.8); MRAC B3–06– P–1–3, ex. CU 95209 (3: 46.3–54.6); SAIAB 187275, ex CU 95209 (3: 45.6–52.6); UF 184234, ex CU 95209 (3: 41.8–64.7).

Non-types. Malagarasi River drainage: CU 90426, Tanzania, Malagarasi River at bridge between Kafuru and Makere, 4°01'32.5”S, 30°33'06.5"E (3:24.6–29.3), CU 90469, Tanzania, Malagarasi River at bridge between Kafuru and Makere, 4°01'32.5”S, 30°33'06.5"E (26: 24.7–46.7); MRAC 47343–362, Burundi, Malagarazi River and its tributaries, (19: 38.7–96.2), MRAC 91030.0217, Burundi, Nyesasa River, trib of Muyovozi River (which is a tributary of the Malagarazi), at bridge on RN8 [now RN11] just before Gihofi, ca. 3°59'S, 30°09'E (1: 51.4); MRAC 91030.0218–0225, Burundi, Kinywa River, Trib of Malagarazi, at the bridge on Route Pr85, near town of Buyaga, ca. 3°55'S, 30°10'E (7: 16.2–69.7); MRAC 91030.0226–0248, Burundi, Nyankanda River, Trib of Malagarazi, in the Fault of the Germans, on Route Pr 85, ca. 3°54'S, 30°13'E (23: 33.5–65.4); MRAC 91030.0249– 0 295, Burundi, Ntanga River, Trib of Malagarazi, at the bridge on Road of General Interest 4, 7 km from Kinyinya, ca. 3°37'39.3”S, 30°17'54.5”E (47: 26.4–76.6); MRAC 91030.0300–0309, Burundi, Musasa River, Trib of Muyovozi, at the bridge on RN8, ± 5 km Rutana, ca. 3°58'44.9”S, 30°01'56.0”E (10: 45.6–71.5); MRAC 91030.0310–0315, Burundi, Mutsindozi River, trib of Malagarazi at bridge on Route RN12, km 39 from Lake Nyanza, ca. 4°05'S, 29°57'E (6: 54.7–67.5); MRAC 91061.0106, Burundi, Musasa River, Trib of Muyovozi, at the bridge on RN8, ± 5 km Rutana, ca. 3°58'44.9”S, 30°01'56.0”E (1: 55.3); MRAC 91062.0896–0923, Burundi, Mutsindozi River, near the sugar refinery, Gihofi, ca. 4°02'S, 30°09'E (28: 29.6–73.1); MRAC 91062.0924–0929, Burundi, Musasa River, Trib of Muyovozi, at the bridge on RN8, ± 5 km Rutana, ca. 3°58'44.9”S, 30°01'56.0”E (6: 36.4–85.9); MRAC 91062.0930–0932, Burundi, Mashuro River, about 5 km from Gihofi towards Giharo, 3°57'37”S, 30°09'54.6”E (3: 28.9–48.7); MRAC 91062.0933, Burundi, Ruru River, trib of Rumpungwe River, on the road towards Cendajuru, ca. 3°19'S, 30°34'E (1: 79.2); MRAC 91062.0950–0957, Burundi, Kabingo, Mazimero River, on Rutana-Kinyinya road, 3°53'01.5”S, 30° 11'54.2”E (8: 37.1–63.1); MRAC 91062.0958–1056, Burundi, Rugoma River, trib of Rumpungwe River, 4 km from Kinyinya, ca. 3°38'S, 30°23'E (99: 24.6–100.9); MRAC 91062.1057–1081, Burundi, Rugaragara River, on Kinyinya-Gisuru road, about ± 20 km from Gisuru, ca. 3°27'S, 30°24'E (25: 25.9–67.7); MRAC 91062.1082–1094, Burundi, Kiruhura River, trib of Mwambu River, zone Muyange, ENE of Cendajuru, ca. 3°16'S, 30°40'E (13: 32.6–71.8); MRAC 91062.1095–1107, Burundi, Nyabigosi River, trib of Rumpungwe River, near Gisuru, ca. 3°29'S, 30°30'E (13: 28.3–68.5); MRAC 91062.1139–1168, Burundi, Gitinwa River, trib of Ruru River, trib of Rumpungwe River, near Cendajuru, before village of Gusiana, ca. 3°20'S, 30°34'E (30: 24.6–83.9); MRAC 91062.1169–1245, Burundi, Mukitcha River, ± 8 km towards Cendajuru from Gasenyi, ca. 3°17'S, 30°36'E (77: 28.7–74.6); MRAC 91079.0055–0058, Burundi, Musasa River, (local name Uruhuzi) 78 km SSE of Gitega, ± 10 km SE of Rutana, 4°00'00”S, 30°06'47.3”E (5: 25.9–71.9); MRAC 93150.0184–0186, Burundi, Mazimero River, on road from Rutana-Kinyinya, ca. 3°54'S, 30°13'E (3: 63.5– 75.9); MRAC 93150.0187–0238, Burundi, Ruru River, about 9 km from Muyaga towards Cendajuru, ca. 3°18'S, 33°13'E (52: 35.4–80.4); MRAC 93150.0239, Burundi, Ntanga River, Trib of Malagarazi, at the bridge on Road of General Interest 4, 7 km from Kinyinya, ca. 3°38'S, 30°18'E (1: 52.7); MRAC 93150.0240–0260, Burundi, Mukazye River (Nyamabuye), 10 km from Giharo towards Kinyinya, ca. 3°47'S, 30°18'E (21: 26.9–72.9); MRAC 93150.0261–0333, Burundi, Idumaniro River, on Cendajuru-Gitwenge road, ca. 3°15'S, 30°39'E (73: 25.8–81.1); MRAC 93150.0351–0359, Burundi, Rumpungwe River, near Gisuru, on road from Kinyinya-Gisuru, ca. 3°27'S, 30°29'E (9: 26.2–74.3); MRAC 93150.0360–0378, Burundi, Kiruhura River, on Cendajuru-Gitwenge road, ca. 3°15'S, 30°39'E (18: 35.8–65.8), MRAC 93150.0379–0382, Burundi, Nyanzari River, on Cankuzo-Mushiha road, near Gishungo, 3°04'25”S, 30°39' 22”E (4: 48.3–68.6); MRAC 93150.0383–0392, Burundi, Mutsindozi River, near the sugar refinery, Gihofi, ca. 4°00'S, 30°40'E (12: 44.2–80.0); MRAC 93152.0613–0622, Tanzania, Malagarazi River, rapids at Uvinza, near salt mine, 5°06'07”S, 30°21'56”E (11: 37.1–59.9); MRAC 93152.0623– 0 643, Tanzania, Nyamgongo River, trib of Malagarazi River, km 46 from Uvinza to Kasulu, 4°48'34”S, 30°12'51”E (21: 28.3–69.0); MRAC 96031.1548–1549, Burundi, Nyarugunga River, km 30 after Kinyinya, on Kinyinya-Gisuru road, ca. 4°52'S, 29°50'E (2: 53.7–58.6); MRAC 96031.1550–1562, Burundi, Nyarugunga River, km 30 after Kinyinya, on Kinyinya–Gisuru road, ca. 4°52'S, 29°50'E (13: 47.6–86.6); MRAC 96031.1563–1570, Burundi, Nyarubare River, km 15 on Kinyinya-Gisuru road, ca. 3°34'S, 30°26'E (8: 45.7–81.8); MRAC 96083.1141, Tanzania, Ruchigi River, 7 km after Kasulu to Kibando, trib of Malagarasi, 4°32'01.4”S, 30°08'58.6”E (1: 71.5); MRAC 96083.1142–1145, Tanzania, Mgandazi River, near Kasulu, ca. 4°37'S, 30°06'E (4: 48.7–72.6). Luiche River drainage: MRAC 93152.0644–0649, Tanzania, Mukuti River, trib. of Luiche River, on road from Kigoma to Kasulu, 4°53'12.1”S, 29°52'12”E (6: 35.0–118.8); MRAC 93152.0650–0651, Tanzania, Mungonya River, trib of Luiche River, ± 10 km from Kigoma, route Kigoma-Kasulu, 4°52'28”S, 29°49'52”E (2: 65.2–90.9); MRAC 93152.0652–0661, Tanzania, Kidahwe River, km 34 on Kigoma-Uvinza road, trib of Luiche River, ca. 4°53'S, 29°48'E (12: 68.6–112.0). Lake Rukwa Basin: MRAC 191055 –057, Zambia, Saisi and Kalambo River, Tunduma road, ca. 9°06'S, 31°29'E (3: 30.6–39.1); MRAC 191092 –113, Zambia, Saisi River, at crossing of Abercorn-Tunduma road, 9°05'38.1”S, 31°29'20.5”E (22: 27.5–104.8); MRAC 191423–424, Zambia, Lumi river, Kawimbe Road, ca. 8°50'S, 31°32'E (2: 31.6–35.4); MRAC 94034.0822–0831, Tanzania, Piti River, 63 km south of Rungwa River on road to Makongolosi, 7°26'48.5”S, 33°25'22.1”E (10: 32.9–66.6); SAIAB 37397, Zambia, Near Mbala, Saisi River at Tunduma Road near Neilsons Farm, ca. 9°05'S, 31°32'E (1: 55.4); SAIAB 38096, Zambia, Saisi River at Tunduma Road bridge, 9°05'39”S, 31°29'22”E (1: 35.8); SAIAB 39557, Zambia, Saisi River at Tunduma Road bridge, ca. 9°05'39”S, 31°29'22”E (1: 57.0); SAIAB 38108, Zambia, Chitungulu stream, Nsunzu Farm, trib of Saisi River, ca. 9°05'S, 31°32'E (2: 54.3–70.3); SAIAB 39543, Zambia, Chitungulu stream, Nsunzu Farm, trib of Saisi River, ca. 9°05'S, 31°32'E (1: 37.6); SAIAB 50333, Tanzania, Lupa River at Lupatingatinga, on Makongolsi-Rungwa road, 8°01'48.9”S, 33°16'18.9”E (1: 42.0). Rufiji basin, Upper Great Ruaha River drainage: SAIAB 59388, Tanzania, Bridge near Chinata on Mbeya-Iringa road, 8°51'35.7”S, 34°01'33”E (31: 49.2–111.7); SAIAB 59397, Tanzania, Great Ruaha River at Route A104 crossing just east of Chimala, 8°51'16.4”S, 34°05'7.0”E (32: 30.3–72.6).

Diagnosis. Diagnostic characters are summarized in Table 2 . Amphilius pedunculus is diagnosed from A. jacksonii , A. ruziziensis and A. lujani by its deeper caudal peduncle (caudal peduncle depth 9.9–12.3% SL vs. 4.8– 9.5% SL), and from A. ruziziensis and A. frieli by its wider interorbital width (28.1–35.8% HL vs. 23.4–27.7% HL). It is distinguished from A. crassus by its longer caudal peduncle (caudal peduncle length 16.0–18.8% SL vs. 13.3–15.5% SL) and shorter dorsal-fin insertion to adipose-fin insertion length (37.5–41.7% SL vs. 42.2–44.6% SL). It is further diagnosed from A. frieli by having fewer total gill rakers on the first gill arch (7–9, rarely 6 or 10 vs. 10–11, rarely 9 or 12).

Description. Morphometric data are in Table 4 . 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, much 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, slightly papillate. Rictal lobe large and slightly 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 (17), or 8 (24) rays. Gill rakers on first epibranchial 2 (20) or 3 (21); rakers on first ceratobranchial 4 (1), 5 (8), 6 (25), or 7 (7); total gill rakers on first arch 6 (1), 7 (4), 8 (16), 9 (16) or 10 (4).

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 or just posterior to tip of pectoral fin. Dorsal fin with i,6 (41) rays, and fin margin straight. Pectoral fin with i,8 (35), or i,9 (6) 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 (41) 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 (40) principal rays. Anal fin with short base, origin posterior to origin of adipose-fin base, with ii,6 (7), ii,7 (2), iii5 (4), iii,6 (27), or iii,7 (1) 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 saddle 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 to black, with posterior distal edge cream-colored. Pectoral and pelvic fins positioned horizontally with upper surfaces cream-colored with dark fin base and dark medial band. Lower surfaces light yellow. Caudal fin creamcolored 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, medial ventral edge, and tip creamcolored.

Distribution. Malagarasi River drainage, western Tanzania and southern Burundi; Luiche River drainage, western Tanzania; Lake Rukwa basin, Tanzania and Zambia; and upper Great Ruaha River system, Rufiji basin, eastern Tanzania ( Fig. 6 ).

Etymology. The diminutive of pes, pedunculus , a noun, refers to the distinctively short and deep caudal peduncle of this species.

Figures

FIGURE 5. Amphilius pedunculus, CU 97334, 52.3 mm SL, holotype; lateral, dorsal and ventral views.

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

Tables

TABLE 4. Morphometric data for Amphilius pedunculus. Range and mean include the holotype.

	Holotype	Range (n=32)	Mean±SD
%SL
Head length	25.7	23.2–26.8	25.1±0.9
Head width	22.0	20.2–22.6	21.0±0.6
Head height	15.3	12.8–16.8	14.6±0.9
Body depth	20.0	14.1–20.2	17.9±1.5
Body depth at anus	16.9	13.7–17.7	15.7±0.9
Predorsal length	37.4	32.7–39.5	37.0±1.3
Prepectoral length	19.5	18.6–22.7	20.1±1.0
Preanal length	72.7	70.1–76.7	72.5±1.7
Dorsal-fin base length	10.9	9.1–13.3	11.4±1.0
Adipose-fin base length	16.8	16.7–23.5	20.2±1.7
Anal-fin base length	11.7	10.0–14.1	11.9±1.1
Pelvic-fin length	19.0	17.7–20.7	19.2±0.7
Pectoral-fin length	21.6	19.7–24.3	22.0±1.1
Anal-fin length	19.3	17.7–21.3	19.8±0.9
Caudal-peduncle length	17.9	16.0–18.8	16.8±0.8
Caudal-peduncle depth	11.4	10.1–12.3	11.3±0.5
Anus to anal fin length	15.5	12.4–16.9	14.9±1.1
Prepelvic length	50.7	47.3–52.1	49.6±1.2
Postpelvic length	50.6	49.2–55.1	51.6±1.3
Dorsal-fin insertion to adipose	40.5	37.5–41.7	40.3±1.0
Dorsal-fin origin to caudal	66.6	62.4–67.9	65.5±1.5
Preanus length	56.5	55.8–61.4	58.3±1.2
%HL
Snout length	48.5	41.7–51.2	46.7±2.4
Interorbital distance	29.8	28.1–35.8	31.6±2.0
Maxillary barbel length	72.5	61.4–98.0	77.3±8.2
Inner mandibular barbel length	40.0	28.3–54.3	41.5±5.7
Outer mandibular barbel length	60.4	44.0–81.0	62.5±8.3
Eye diameter	15.1	14.0–19.3	16.1±1.3