Labeo meroensis, Moritz, Timo, 2007

Moritz, Timo, 2007, Description of a new cyprinid species, Labeo meroensis n. sp. (Teleostei: Cyprinidae), from the River Nile, Zootaxa 1612, pp. 55-62 : 56-59

Labeo meroensis , new species.

( Figures 1–3 , Table 1 )

Holotype: BMNH 2006.11.9.1: River Nile at Shendi (N 16°42'05'', E 33°25'37''), Republic of Sudan. Collection date: 12.01.2006; collectors: T. Moritz and V. von Vietinghoff.

Paratypes: BMNH 2006.11.9.2–8, 7 specimens, same data as holotype; BMNH 2006.11.9.9–10, 2 specimens, cleared and double stained following the protocol of Talor & van Dyke (1985), same data as holotpye; MRAC A6-46-P-1-3, 3 specimens, same data as holotype; BMNH 2006.11.9.11–13, 3 specimens River Nile at Atbara (city) below mouth of River Atbara (N 17°14'21'' E 33°58'07''). Collection date: 14.01.2006; collectors: T. Moritz and V. von Vietinghoff.

Differential diagnosis. Labeo meroensis n. sp. is distinguished from all other Nilotic Labeo species by having only 5.5 scale rows between lateral line and mid-dorsal line (vs. 6.5 or more). It differs from all other African Labeo except L. djourae and L. nunensis by the combination of the following characters: cylindriform body, transverse plicae on the inner surface of the lips, 5.5 scale rows between lateral line and mid-dorsal line, 39 to 41 scales in lateral line and 16 scales around the caudal peduncle. Labeo meroensis n. sp. is distinguished from L. djourae from the Chad and Benue systems and L. nunensis from the Sanaga river in Cameroon by having a larger eye diameter (21.5–27.4% of head length vs. 14.5–20.8% in L. djourae and 14.0% in the type material of L. nunensis ). The dorsal fin of L. nunesis Pellegrin, 1929 bears an anterior filament, which is not present in L. meroensis . Labeo djourae differs furthermore from L. meroensis n. sp. in having a longer snout (46.7–55.9% vs. 32.2–41.4% of head length), larger interorbital width (35.0–50.0% vs. 30.5–38.5% of head length) and a prominent emargination in the dorsal snout region which is absent in L. meroensis n. sp.

Description. Description based on the holotype and 15 paratypes. Labeo meroensis n. sp. is a small species with a maximum size in the type series of 52.5 mm SL. Body cylindriform; inner surface of lips with transverse plicae. Counts and proportional measurements are presented in Table 1 . Two pairs of barbels present: maxillary barbels well developed, but mostly hidden with only tip reaching beyond jaw articulation ( Fig. 3 ); rostral barbels small. Anterior nasal opening with well developed tube. Eyes large, in lateral position: visible in dorsal but not in ventral view. Prominent breeding tubercles sometimes developed.

Dorsal fin concave with 4 unbranched and 10 branched rays; without filamentous extension. Three of the unbranched rays supranumerary, at least anterior one only visible in cleared and stained specimens or x-rays. Pectoral fins low, laterally positioned on the body, reaching level of dorsal-fin base. Pectoral fin with 16 to 23 rays. Pectoral and pelvic fins broadly separated. Pelvic fins insert about in middle of dorsal fin and reach beyond anus. Anus 3 to 4 scale rows in front of anal fin. Pelvic fins consist of one unbranched, seven branched and again one unbranched ray. Caudal fin deeply notched with pointed dorsal and ventral lobes, consisting of 10 upper and 9 lower principal rays plus 10 – 11 upper and 7 – 10 lower procurrent rays. 39 to 41 scales in the lateral line, 5.5 scale rows between dorsal-fin origin and lateral line and 3.5 to 4.5 scales between lateral line and origin of pelvic fin. Vertebral column with 38 vertebrae (18 – 19 abdominal; 19 – 20 caudal vertebrae). Dorsal fin inserts after neural spine of vertebra number nine; anal fin inserts after haemal spine of vertebra 26 to 28, usually 27.

Coloration. Live specimens with dark-olive back with silvery reflection ( Fig. 2 ). Towards to horizontal septum the coloration becomes more greenish. A narrow, almost golden reflecting band about one scale row above the horizontal septum. Along flank a broad grey band continuing on to the head. Belly clear white; some melanophores only on ventral side of snout. Fins transparent; only some melanophores in dorsal fin and along upper and lower border of caudal fin. Upper half of eye conspicuously orange ( Fig. 2 ).

Fixed specimens with brown back without reflections; belly pale. Grey band along flank hardly visible and completely absent from head. Fins less transparent and orange tint of eye absent.

Distribution and habitat. The species is so far only known from the two collecting sites listed in this study ( Fig. 4 ): the river Nile between the 6th and 5th cataract at Shendi ( Fig. 5 ) and Atbara (city, not river). Most specimens were found in flowing shallow water over sand; one specimen was collected in submerged shore vegetation. Water parameters for Shendi were 158 µS, 23.2 °C, pH 8.23 at the 12.01.0 6 and for Atbara 168 µS, 20.5 °C, pH 8.30 at the 14.01.0 6.

Etymology. Named in reference to the ancient Nubian capital Meroe positioned at the River Nile between Shendi and Atbara, where the types have been collected.

Morphometric Holotype Paratypes (N = 15) characters Mean Min Max Standard length (SL) in mm 45.9 46.4 40.0 52.5

Figures

FIGURE 1. Labeo meroensis n. sp., BMNH 2006.11. 9.1, 46.9 mm SL.

FIGURE 2. Live specimen of Labeo meroensis n. sp. from River Nile at Shendi, 12.01. 2006.

FIGURE 3. Ventral view of mouth of Labeo meroensis n. sp., BMNH 2006.11. 9.1, 46.9 mm SL.

FIGURE 4. Map of a part of the river Nile within the Republic of Sudan. Labeo meroensis n. sp. was collected in Shendi and Atbara (city, not river).

FIGURE 5. Type locality of Labeo meroensis n. sp.: river Nile at Shendi, Republic of Sudan. View upstream (above) and view to the shore (below) from middle of river.