Hepsetus akawo, Decru & Vreven & Snoeks, 2011

Decru, E., Vreven, E. & Snoeks, J., 2011, A revision of the West African Hepsetus (Characiformes: Hepsetidae) with a description of Hepsetus akawo sp. nov. and a redescription of Hepsetus odoe (Bloch, 1794), Journal of Natural History 46 (1 - 2), pp. 1-23 : 13-19

Hepsetus akawo sp. nov.

Type material

Holotype. MRAC 73-5 -P-465; 211.5 mm; Anecho, lagune (± 06 ◦ 14 ′ N, 01 ◦ 35 ′ E), Coll. D. Thys van den Audenaerde (10 September 1966).

Paratypes. MRAC 73-5 -P-457-459; n = 2; 194.5–221.5 mm; Dunkwa, riv. Ofin (05 ◦ 58 ′ N, 01 ◦ 47 ′ W) Coll. D. Thys van den Audenaerde (22 September 1966) .

MRAC 87-18 -P-762; 200.0 mm; Kosua, small tributary of the Wawa River near Dodi- Papase (07 ◦ 42 ′ N, 00 ◦ 29 ′ E); Coll. G. Teugels (17 February 1987) .

MRAC 73191 (ex. MRAC 73191-73192 ); n = 1; 167.5 mm; Abomey-Calavi (06 ◦ 27 ′ N, 02 ◦ 21 ′ E) Coll. Cadenat, J.

MRAC 73-1 -P-428; 189.5 mm; Porto Novo, lagune (06 ◦ 29 ′ N, 02 ◦ 37 ′ E); Coll. P. De Kimpe (15 November 1963) .

MRAC 80-16 -P-8; 221.0 mm; Asejura lake, Oshun riv., Dugbe market Ibadan (07 ◦ 20 ′ N, 04 ◦ 10 ′ E); Coll. G. Teugels & L. Risch (2 May 1980) .

Diagnosis

Hepsetus akawo can be distinguished from all other Hepsetus species by the following unique combination of characters: number of lateral line scales, low: 43–51; nostril-lower jaw distance, short: 36.6–42.1 (mean 39.6) % HL (Figure 3); number of gill rakers, high: 17–23; number of scales between dorsal fin and lateral line: 71 / 2 – 91 / 2 number of scales between adipose fin and lateral line: 41 / 2 – 61 / 2 head width, broad: 32.8–42.3 (mean 37.0) % HL; and internasal distance, high: 21.9–28.3 (mean 24.7) % HL.

Description

The holotype is illustrated in Figure 6 . Maximum observed size: 277.5 mm SL. Meristic and morphometric data are given in respectively Table 5 and 6.

Head broad but shallow, with a relatively long but broad snout. Body elongated and broad, which gives it a plump appearance. Dorsal and anal fins, though in a posterior position in all Hepsetus species , are more anteriorly positioned relatively to the other Hepsetus . Small number of lateral line scales and a large number of quite small gill rakers on the epibranchiale of the first gill arch.

Differential diagnosis

Hepsetus akawo can be distinguished from H. odoe by a smaller number of total lateral line scales [43–51 vs 50–60 (exceptionally 49)], and by a lower nostril-lower jaw distance [36.6–42.1 (mean 39.6) % HL vs 40.4–47.6 (42.6) % HL].

Hepsetus akawo can be distinguished from H. cuvieri by a higher number of gill rakers (17–23 vs 8–13), a lower number of scales between dorsal fin and lateral line (71 / 2 – 91 / 2 vs 101 / 2 – 111 / 2); a lower number of scales between adipose fin and lateral line (41 / 2 – 61 / 2 vs 61 / 2 – 71 / 2); and by a broader head width: 32.8–42.3 (mean 37.0 % HL vs 27.8–40.4 (33.5) % HL; a larger interorbital distance 28.0–34.9 (mean 31.7) % HL vs 23.7–32.6 (28.2) % HL; and a larger internasal distance 21.9–28.3 (mean 24.7) % HL vs 18.0–26.8 (20.8) % HL. The latter three characters are positively allometric.

Colouration (in alcohol)

Dorsal side of head and body brownish, with a gradual change from darker to lighter tones on the flanks. Entirely yellowish ventrally. Some specimens darker brownish and more uniformly coloured. A vague horizontal line pattern on the flanks, from anterior border of adipose fin (occasionally from posterior border of dorsal fin) to caudal fin base, resulting from the scales having a darker upper and lower border, whereas the remaining part of the scales remains paler. These lines cover the flanks from approximately three scale rows above lateral line down to two scale rows below the lateral line. Sometimes series of 10 to 16 greyish vertical bands are present on the dorsolateral body parts. The presence of these bands appears to be linked to stress (personal observation). Rounded dorsoventrally elongated blackish spot behind head and just above lateral line.

Posterior part of head with three, well-marked, dark brownish bands running from posterior border of the eye to anterior edge of preopercle. Bands sometimes faded and poorly visible. Lower half of postopercle brownish, sometimes blackish. Rounded dorsoventrally elongated blackish spot behind the head, above the lateral line.

All fins but the adipose fin yellowish to dark brownish (more or less the same as body colour); distally translucent. Caudal fin translucent, in mid-centre and proximally on upper and lower lobes. Dorsal, anal and caudal fins with prominent small, roundish, dark-brown spots. Spots on fins more prominent on larger specimens (±> 150 mm SL). Adipose fin base yellowish to darker brownish, black distally.

Distribution

Within West Africa, H. akawo is restricted to the easternmost part of the region, i.e. from the Sassandra River ( Ivory Coast) in the west to the Shari River ( Central African Republic) in the east and the Cross River ( Cameroon / Nigeria) in the southeast

( Figure 5 ). Elsewhere it also occurs in Lower Guinea, from the Cross ( Cameroon) to the Kribi River ( Cameroon) (see additional specimens examined).

Etymology

The specific name refers to the local names in the Adangme language of Hepsetus specimens in Ghana: “ Akawo nyagbe ”, which means “dog-like teeth” and “ akawo ” which means “attacker” or “predator” ( Dankwa 2003).

Additional specimens examined (ordered by river system; all sizes as SL)

Sassandra: MRAC 73-5 -P-466; 184.5 mm; Guiglo, riv. Nzo (06 ◦ 33 ′ N, 07 ◦ 29 ′ W) . MRAC 73-10 -P-961; 160.5 mm; Guiglo, riv. Nzo (06 ◦ 33 ′ N, 07 ◦ 29 ′ W) . MRAC 85- 55 -P-128; 108.0 mm; riv. N’Zo, tribut. Du Sassandra à Guiglo (06 ◦ 33 ′ N, 07 ◦ 29 ′ W) . MRAC 86-13 -P-21; 234.5 mm; riv. Méné, sur la route entre San Pedro et Sassandra (05 ◦ 02 ′ N, 06 ◦ 31 ′ W) .

Bandama: MRAC 74-14 -P-2765; 277.5 mm; lac Kossou (07 ◦ 10 ′ N, 05 ◦ 20 ′ W) .

Bia: MRAC 80-19 -P-41; 178.0 mm; lagune Ebrié à Layo (05 ◦ 19 ′ N, 04 ◦ 19 ′ W) . MRAC 95-014 -P-0235-0238; 202.0–222.0 mm; Ayamé, lac d’Ayamé (05 ◦ 36 ′ N, 03 ◦ 09 ′ W) . MRAC 74-14 -P-2581; 149.0 mm; lac Kossou (07 ◦ 10 ′ N, 05 ◦ 20 ′ W) . MRAC 95- 014 -P-0240-0242., 194.0–219.0 mm; Bianouan, riv. Bia (06 ◦ 01 ′ N, 03 ◦ 12 ′ W) .

Volta Noire : MRAC 143762-763 ; 196.5–217.5 mm ; Volta Noire (11 ◦ 34 ′ N, 02 ◦ 50 ′ W // 12 ◦ 45 ′ N, 04 ◦ 18 ′ W). MRAC 141116 ; 134.5 mm; riv. Bougouriba, afflt. De la Volta Noire (10 ◦ 56 ′ N, 03 ◦ 39 ′ W) .

Volta Rouge : MRAC 143761 ; 226.0 mm; petite afflt. de la Volta Rouge, près Kokologho, route Ouagadougou-Koudougou (12 ◦ 10 ′ N, 01 ◦ 51 ′ W) .

Pra: MRAC 73-5 -P-460; 125.5 mm; Dunkwa, riv. Ofin (05 ◦ 58 ′ N, 01 ◦ 47 ′ W). MRAC 73-5 -P-461; 92.5 mm; Dunkwa, riv. Ofin (05 ◦ 58 ′ N, 01 ◦ 47 ′ W) .

Lake Volta / Rivers: MRAC 73-7 -P-27; 165.5 mm; Anpem , lac Volta (06 ◦ 40 ′ N, 00 ◦ 25 ′ W) . MRAC 73-11 -P-54; 222.0 mm; Fazao alt: 500 m (08 ◦ 42 ′ N, 00 ◦ 46 ′ E) . MRAC 73-11 -P-55; 193.0 mm; Fazao alt: 500 m (08 ◦ 42 ′ N, 00 ◦ 46 ′ E) .

Mono: MRAC 73-14 -P-50-51; 126.5–138.0 mm; Dotékopé, riv. Mono (woodland + galerijwoud) alt: 150 m (07 ◦ 49 ′ N, 01 ◦ 18 ′ E) . MRAC 73-14 -P-52; 134.5 mm; Ogbone (07 ◦ 46 ′ N, 01 ◦ 19 ′ E) . MRAC 73-5 -P-462-464; n = 4 (instead of 3); 97.5–109.5 mm; Corrékopé, riv. Mono (07 ◦ 48 ′ N, 01 ◦ 16 ′ W) . MRAC 73192 (ex. MRAC 73191-73192 ); n = 1; 125.0 mm; Abomey-Calavi (06 ◦ 27 ′ N, 02 ◦ 21 ′ E) . MRAC 90-13 -P-1; 139.0 mm; lac Nokoue, station de Ganvie (06 ◦ 28 ′ N, 02 ◦ 25 ′ E) . MRAC 73-1 -P-425; 125.0 mm; Awansouri, lac Nokoué (06 ◦ 23 ′ N, 02 ◦ 26 ′ E) .

Lower Niger: MRAC 91-10 -P-301-302; 137.5–142.0 mm; Akpor , New Calabar River (04 ◦ 52 ′ N, 06 ◦ 54 ′ E) . MRAC 90-19 -P-72; 126.0 mm; Elele-Alimini , New Calabar River (05 ◦ 03 ′ N, 06 ◦ 44 ′ E) . MRAC 91-01 -P-80; 118.5 mm; Odieke , Orashi River (05 ◦ 01 ′ N, 06 ◦ 27 ′ E) . - MRAC 91-055 -P-0236; 142.0 mm; Forcados River , about 1 km west of Oboro and 7 km northwest of Bomadi (05 ◦ 11 ′ N, 05 ◦ 52 ′ E) .

Cross: MRAC 86-39 -P-2; 217.0 mm; Itu bridge , Cross River (05 ◦ 11 ′ N, 08 ◦ 03 ′ E). MRAC 88-03 -P-12-13; 100.0–164.0 mm; site 2: Calabar , Cross River (04 ◦ 58 ′ N, 08 ◦ 19 ′ E) .

Shari: MRAC 73-26 -P-46; 266.5 mm; région au sud de Hollom (11 ◦ 10 ′ 20 ′′ N, 15 ◦ 03 ′ 10 ′′ E) . MRAC 82-13 -P-1015; 201.5 mm; campement de Gounda, riv. Gounda (09 ◦ 13 ′ N, 21 ◦ 00 ′ E) . MRAC 82-13 -P-1014; 265.0 mm; riv. Gounda, pont route Ndele- Birao (08 ◦ 33 ′ N, 21 ◦ 30 ′ E) .

Benoué: MRAC 73-15 -P-21; 198.0 mm; Garoua (gekocht) (09 ◦ 18 ′ N, 13 ◦ 24 ′ E). MRAC 73-15 -P-215; 276.5 mm; Garoua, riv . Benoué (09 ◦ 18 ′ N, 13 ◦ 24 ′ E) .

Cross: MRAC 88-53 -P-113-114; 53.5–120.5 mm ; Cross basin, small stream on Bamenda-Mamfé road, 98 km southwest of Bamenda, 24 km north of Mamfé (05 ◦ 43 ′ N, 09 ◦ 27 ′ E) . MRAC 73-40 -P-22; 274.0 mm; Nguti, Ohumbe River on the Mamfe road (05 ◦ 18 ′ N, 09 ◦ 26 ′ E) . MRAC 73-40 -P-21; 257.5 mm; Nguti, under the bridge, Ohumbe River (05 ◦ 18 ′ N, 09 ◦ 26 ′ E) .

Additional specimens identified (ordered by river system; all sizes as SL)

Sassandra : MRAC 86-13 -P-22-30; 22.0– 30.1 mm; riv. Méné, sur la route entre San Pedro et Sassandra (05 ◦ 02 ′ N, 06 ◦ 31 ′ W). MRAC 86-13 -P-31; 219.2 mm; Grand Gallo, riv. Nieri (04 ◦ 47 ′ N, 06 ◦ 56 ′ W) .

Bandama: MRAC 87-18 -P-756-758; 28.3–32.0 mm; riv. N’Zi , sur la piste entre Katiola et Dabakala (08 ◦ 14 ′ N, 04 ◦ 51 ′ W). MRAC 87-18 -P-759; 25.2 mm; riv. Maraoué, à env. 15 km de Mankono sur la piste entre Mankono et Séguéla (08 ◦ 07 ′ N, 06 ◦ 42 ′ W) .

Bia: MRAC 86-18 -P-335; 126.2 mm; Koui (= Koun) près de Yaou, riv. La Bia (07 ◦ 30 ′ N, 07 ◦ 16 ′ W) . MRAC 173384-385 ; 111.5–129.5 mm; lagune Ebrié (05 ◦ 09 ′ N, 04 ◦ 00 ′ W // 05 ◦ 19 ′ N, 04 ◦ 52 ′ W) . MRAC A0-046-P-0004; 208.5 mm; riv. Niouniourou (± 5 ◦ 06 ′ N, 5 ◦ 29 ′ E) . MRAC 74-17 -P-292-297; 260.5–294.5 mm; lac Kossou (07 ◦ 10 ′ N, 05 ◦ 20 ′ W // 07 ◦ 00 ′ N, 05 ◦ 30 ′ W) . MRAC 95-014 -P-239; 251.5 mm; riv. Agneby , pont autoroute (05 ◦ 29 ′ N, 04 ◦ 14 ′ W) .

Tano: MRAC 85-29 -P-243-244; 145.2–167.3 mm; Noe, riv. Tano (05 ◦ 18 ′ N, 02 ◦ 47 ′ W) .

Comoe: MRAC A0-044-P-0049; 31.0 mm; affl. sec. Mamou, ont près d’Annepé, bassin Mé (05 ◦ 54 ′ N, 03 ◦ 46 ′ W) . MRAC 86-18 -P-1296; 36.0 mm; Yakassé-Attobrou, riv. La Mé (05 ◦ 49 ′ N, 03 ◦ 57 ′ W) . MRAC A0-046-P-0050; 110.5 mm; riv. Mé, 3km E. d’Annepé (05 ◦ 54 ′ N, 03 ◦ 45 ′ W) . MRAC 97-27 -P-1; 18.0 mm; Wiawso (06 ◦ 12 ′ N, 02 ◦ 29 ′ W) .

Pra: MRAC 87-18 -P-760-761; 22.0– 57.5 mm; Ofin River near Ahenkro , between Kumasi and Ofinso (06 ◦ 53 ′ N, 01 ◦ 38 ′ W) .

Lake Volta / Rivers: MRAC 94-011 -P-0014; Densu River at Koforidua (06 ◦ 05 ′ N, 00 ◦ 22 ′ W) .

Ouéme: MRAC 73-01 -P-426-467; 108.6–144.5 mm; Porto Novo, lagune (06 ◦ 29 ′ N, 02 ◦ 37 ′ E) .

Lower Niger: MRAC 91-10 -P-295-300; 104.7–153.7 mm; Akpor, New Calabar River (04 ◦ 52 ′ N, 06 ◦ 54 ′ E) .

Niger: MRAC 76-32 -P-1228; 29.2 mm; ro 69/1 mellem Lafia og Akwanga (08 ◦ 29 ′ N, 08 ◦ 31 ′ E) . MRAC 76-32 -P-1937; 14.0 mm; bro 63/3 v. for Bida pa Jebba vejen (09 ◦ 05 ′ N, 06 ◦ 01 ′ E) .

Bénoué: MRAC 73-15 -P-217; 212.2 mm; Garoua, riv . Benoué (09 ◦ 18 ′ N, 13 ◦ 24 ′ E). MRAC 76-14 -P-227; 153.0 mm; Touroua, riv. Faro (09 ◦ 05 ′ N, 12 ◦ 58 ′ E) .

Wouri: MRAC 73-29 -P-702; 147.5 mm; Tondé, riv. Sandjé, Wouri bekken (04 ◦ 13 ′ N, 09 ◦ 50 ′ E) . MRAC 73-2 -P-984-987; 115.0–138.0 mm; Deido, riv. Wouri, 4 km en amont du pont à Douala (04 ◦ 04 ′ N, 09 ◦ 43 ′ E) . MRAC 73-29 -P-707; 142.0 mm; Yabassi, riv. Wouri (04 ◦ 27 ′ N, 09 ◦ 58 ′ E) . MRAC 73-29 -P-702; 147.5 mm; Tondé, riv. Sandjé, Wouri bekken (04 ◦ 13 ′ N, 09 ◦ 50 ′ E) . MRAC 73-2 -P-984-987; 115.0–138.0 mm; Deido, riv. Wouri, 4 km en amont du pont à Douala (04 ◦ 04 ′ N, 09 ◦ 43 ′ E) . MRAC 73-29 -P-707; 142.0 mm; Yabassi, riv. Wouri (04 ◦ 27 ′ N, 09 ◦ 58 ′ E) .

Sanaga: MRAC 73-08 - 85-86 ; 186.5–189.0 mm; Edea, riv. Sanaga (03 ◦ 48 ′ N, 10 ◦ 08 ′ E) . MRAC 95-089 -P-1546 (ex. MRAC 95-089 -P1545-1546); 79.5 mm; riv. Djin à Djin, sur la route de Yoko, Sanaga Moyen (05 ◦ 26 ′ N, 12 ◦ 19 ′ E) . MRAC 73- 2 -P-976-977; 208.0– 218.5 mm; Edéa, riv. Sanaga, en aval du pont (03 ◦ 48 ′ N, 10 ◦ 08 ′ E) .

Kribi: MRAC 77-17 -P-3; 139.0 mm; 16 km south east of Kribi (02 ◦ 57 ′ N, 09 ◦ 54 ′ E) .

Figures

Figure 5. Distribution of Hepsetus odoe and Hepsetus akawo based on the examined specimens from West Africa. Localities of H. odoe indicated by open circles; and for H. akawo large filled triangle indicates type locality; smaller filled triangles indicate other localities.

Figure 6. Lateral view of Hepsetus akawo, holotype, MRAC 73-5-P-465, 211.5 mm standard length, Anecho lagune, Togo.