Labeobarbus nzadimalawu, Vreven & Musschoot & Decru & Lunkayilakio & Obiero & Cerwenka & Schliewen, 2019

L. NZADIMALAWU SP. NOV. × L. NZADINKISI SP. NOV.

( FIG. 8 C–E; TABLES 11, 12)

In general, within the Inkisi basin, the hybrids can be identified by the following unique combination of mouth phenotype related characters ( Fig. 8C–E): (1) the absence of a free mental lobe, although an attached or rudimentary lobe can sometimes be present, (2) most often at least a single, well-developed pair of barbels (i.e. the posterior one) and (3) the presence of quite well-developed fleshy lips on the lateral side of the lower jaw (for details see Table 1). Measurements and counts are provided in Tables 11 and 12. The Inkisi hybrids, as for the parental species, are rather small. Maximum observed size, ± 207 mm SL.

Within the Congo basin, the L. nzadimalawu × L. nzadinkisi hybrids can be distinguished from all Labeobarbus species as follows: from L. altipinnis , L. ansorgii , L. batesii , L. brauni , L. cardozoi , L. caudovittatus , L. dartevellei , L. fasolt , L. habereri , L. humphri , L. iphthimostoma , L. iturii , L. jubbi , L. longidorsalis , L. longifilis , L. lufupensis , L. macroceps , L. macrolepidotus / cf. macrolepidotus , L. macrolepis , L. mawambi , L. mawambiensis , L. mirabilis , L. nanningsi , L. oxyrhynchus , L. paucisquamatus , L. stappersii , L. trachypterus , L. upembensis and L. wittei by their high number of lateral line scales, i.e. 35–41 (vs. less than 34); from L. leleupanus by their low lumber of lateral line scales, i.e. 35–41 (vs. 45–47); from L. tropidolepis and L. platyrhinus by their low number of scales between the lateral line and the dorsal and ventral midline, 4.5–5.5 and 4.5–5.5 (vs. 7.5–8.5 and 7.5– 9.5 in L. tropidolepis and 6.5–7.5 and 6.5–8.5 in L. platyrhinus ) and from the latter by their low number of circumpeduncular scales, i.e. 12–14 (vs. 16–18); from L. robertsi by the absence of papillae on the anterior edge of the lower jaw (vs. with well identifiable papillae); from L. progenys by their non-prognathous lower jaw (vs. lower jaw clearly prognathous); from L. altianalis and L. gestetneri by the last unbranched dorsal-fin ray not being transformed into a well-developed spine, but instead being clearly segmented over about half its length, i.e. 37.5–53.5% SL [vs. last unbranched dorsal-fin ray transformed into a spine, clearly segmented only at its most distal end, i.e. less than 6.0% SL (data missing for holotype of L. somereni as the segmented part of the dorsal spine is broken off)]; from, L. pellegrini by their short prepelvic length, i.e. 46.6–48.5% SL (vs. 50.6% SL in L. pellegrini ); their short pelvic length, i.e. 17.9–21.0% SL (vs. 21.8% SL in L. pellegrini ); and their large eye, i.e. 29.1–34.6% HL (vs. 27.1% HL, in L. pellegrini ); and from L. somereni , by their high total number of gill rakers on the first gill arch, i.e. 18–22 (vs. 11) and a, positively allometric, narrow mouth width, i.e. 16.1–26.5% HL (vs. 31.3% HL). Further, the intermediate/hybrid specimens can be distinguished from both the other members of the Inkisi complex, L. nzadimalawu and L. nzadinkisi sp. nov., by the lack of a free mental lobe and, in most cases, the lack of a cornified Varicorhinus real cutting edge on the outer edge of the lower jaw as well (vs. always with a free mental lobe in L. nzadimalawu , and always with a cornified Varicorhinus real cutting edge on the outer edge of the lower jaw and with poorly developed fleshy lips on the lateral sides of the lower jaw in L. nzadinkisi ). In those cases where the intermediate/hybrid specimens bear a cornified Varicorhinus real cutting edge, they also have at least one pair of well-developed barbels (vs. no barbels in L. nzadinkisi ). Finally, the intermediate/ hybrid specimens can be distinguished from Acapoeta tanganicae by its low number of lateral line scales, i.e. 35–41 (vs. 57–67).

Within the adjacent Lower Guinea ichthyofaunal province, the L. nzadimalawu × L. nzadinkisi hybrids can be distinguished from L. axelrodi , L. batesii , L. brevispinis , L. cardozoi , L. caudovittatus , L. compiniei , L. habereri , L. fimbriatus , L. jaegeri , L. malacanthus , L. mariae , L. mbami , L. micronema , L. mungoensis , L. roylii , L. sandersi , L. semireticulatus , L. steindachneri , L. tornieri , L. versluysii and L. werneri by their higher number of lateral line scales, i.e. 37–41 (vs. less than 34 scales); from L. aspius , L. lucius and L. progenys by their non-prognathous lower jaw (vs. lower jaw clearly prognathous); and from L. rocadasi by their last unbranched dorsal-fin ray not being transformed into a well-developed spine, but instead being clearly segmented over approximately half its length, i.e. 37.5–53.5% SL (vs. last unbranched dorsal-fin ray transformed into a spine, clearly segmented only at its most distal end). Finally, the intermediate/ hybrid specimens can be distinguished from Sanagia velifera by their high number of lateral line scales, 35–41 (vs. 22–24).

Within the adjacent Quanza ichthyofaunal province, the L. nzadimalawu × L. nzadinkisi hybrids can be distinguished from L. ansorgii , L. gulielmi L. jubbi , L. nanningsi , L. rhinophorus , L. rosae and L. roylii by their high number of lateral line scales, i.e. 35–41 (vs. less than 34); from L. clarkeae , L. ensifer and L. varicostoma by the absence of papillae on the anterior edge of the lower jaw (vs. with well identifiable papillae); from L. lucius and L. progenys by their non-prognathous lower jaw (vs. lower jaw clearly prognathous); and from L. ensis , L. girardi , L. boulengeri [previously L. latirostris ( Boulenger, 1910) ], L. steindachneri , L. stenostoma and L. rocadasi by their last unbranched dorsal-fin ray not being transformed into a well-developed spine, but instead being clearly segmented over approximately half its length, i.e. 37.5–53.5% SL (vs. last unbranched dorsal-fin ray transformed into a spine, clearly segmented only at its most distal end).

Tubercles ( Fig. 20) are present on all examined specimens (105.6–206.5 mm SL) and, as such, are most likely present in males and females (not dissected to identify sex). They are apparently present all over the year as one specimen collected in February (small dry season) and several ones collected from August to October (the second half of the major dry season and the beginning of the wet season) (see Wamuini Lunkayilakio, 2010) all have them. Usually, tubercles are present all over the snout, i.e. from the dorsal region of the snout and lateral snout sides between angle of fleshy lips and eye and all over the dorsum of head up to nape, i.e. between the posterior edge of the head and the anterior edge of the predorsal area. Some specimens had a small number of tubercles below eyes, i.e. at the level of the infraorbital bones. A few specimens had tubercles on the cheek and two specimens, of 117.7 and 196.4 mm SL, respectively, up to the area of the preopercular/opercular skin fold. Finally, remainder of body without tubercles. Tubercles are easiest observable in one of the largest specimens examined [MRAC A6-007-P-0459-0460: 161.1 (09/10/2005)].

Lateral line scales of the examined specimen ( Fig. 21) with less sinuous but parallel, and even somewhat converging, striae. Number of striae on the posterior edge of these scales between about 28–33.

The pharyngeal teeth number of the only dissected specimen is 2.3.5. (left) – 4.3.2. (right), with the first tooth of the inner row absent on the right pharyngeal bone ( Fig. 22). Note that on the left pharyngeal bone there is an additional small tooth present median of the inner row, which is not firmly attached to the bone but is rather loosely embedded in the surrounding soft tissue.

Live colour pattern most comparable to that of L. nzadinkisi , i.e. silvery grey on lateral sides of head and body. Dorsal midline of head blackish. Dorsal midline of body, in front, along and behind the dorsal fin, with a yellowish-green silver hue. Proximal part of scales, i.e. scale pockets, darker in colour and this especially for the scales above the lateral line. Fins of comparable blackish overall colour with their distal margins whitish translucent. Fin rays whitish. Ventral side of head and body yellowish-white.

Preserved specimens with a uniformly brownish overall body colour, becoming darker towards the dorsal midline of head and body. Scale pockets, especially those above the lateral line, typically darker brown. Anteriormost ventral part of snout and jaws, ventral side of head and belly yellowish light brown. Fins whitish translucent and even transparent with sparsely set minute blackish melanin dots. In at least one of the large-size specimens, the marked distinct scale pocket coloration is absent (MRAC A6-007-P-0538) (207 mm SL). Head generally somewhat lighter of colour compared to body. Fin tissue dark brown, blackish due to the presence of numerous minute dark brown, blackish melanin dots. Fins rays generally more white-yellowish except, sometimes, for the longest upper and lower rays of the caudal fin, which are also dark brown or blackish. Distal edge of fins still whitish translucent and sometimes even transparent.

Hybrids, as for both parental species, seem to be endemic to the Inkisi River basin above the Zongo Falls ( Fig. 23). Currently only known from the DRC part of the basin.

Specimens examined: MRAC A6-007 View Materials -P-0459-0460, Inkisi River basin, Ngufu River, at bridge village Luangu & Kavuaya, Lower Congo ( DRC) (5°04’44.2’ S-15°07’51.0 ’E) Coll. Lower Congo Expedition 2005, 09/10/2005 (140.3–161.1 mm SL) (DNA tag n°621– 622) – MRAC A6-007 View Materials -P-0536-0537, Inkisi River basin, Ngufu River, at bridge village Luangu & Kavuaya, Lower Congo ( DRC) (5°04’44.2’ S-15°07’51.0 ’E) Coll. Lower Congo Expedition 2005, 09/10/2005 (146.1–157.3 mm SL) (DNA tag n°619–620) – MRAC A6-007 View Materials -P-0538, Inkisi River basin, Ngufu River , at bridge village Luangu village Kavuaya, Lower Congo ( DRC) (5°04’44.2’ S-15°07’51.0 ’E) Coll. Lower Congo Expedition 2005, 09/10/2005 (206.8 mm SL) (DNA tag n°615) – MRAC A7-009 View Materials -P-0851-0852, Inkisi River basin, Ngeba / Ngufu River , village Ngeba, Lower Congo ( DRC) (5°11’01.5’ S-15°12’23.1 ’E) Coll. S. Wamuini Lunkayilakio, 25/08/2006 (125.6–130.3 mm SL) (DNA tag n°685 & 688) – MRAC A7-009 View Materials -P-0853, Inkisi River basin, Nua River , village Mawunzi, Lower Congo ( DRC) (5°18’48.0’ S-15°16’31.9 ’E) Coll. S. Wamuini Lunkayilakio, 14/02/2007 (129.5 mm SL) (DNA tag n°782) – MRACA7-009 -P-0856-0857, Inkisi River basin, River Lukusu , village Ngeba / Mboma, Lower Congo ( DRC) (5°13’36.9’ S-15°13’02.0 ’E) Coll. S. Wamuini Lunkayilakio, 23 August 2006 (117.7–196.4 mm SL) (DNA tag n°662–663) – MRAC A7-009 View Materials -P-1173, Inkisi River basin, Nsanga village, downstream of dam, Lower Congo ( DRC) (4°50’39.4’ S-14°57’27.5 ’E) Coll.S.Wamuini Lunkayilakio, 23 September 2006 (145.0 mm SL) (DNA tag n° 896) – MRAC A7-009 View Materials -P-1372, Inkisi River basin, riv. Muala , village Muala-Kinsende, Lower Congo ( DRC) (5°16’11.4’ S-14°57’42.1 ’E) Coll. S. Wamuini Lunkayilakio, 11 July 2006 (114.8 mm SL) (DNA tag n°813) – MRAC A7-009 View Materials -P-1373, same data (114.4 mm SL) (DNA tag n°814) – MRAC A7-009 View Materials -P-1376, Inkisi River basin, riv. Mingididi , village Mawunzi, Lower Congo ( DRC) (5°19’20.0’ S-15°16’49.9 ’E) Coll. S. Wamuini Lunkayilakio, 14 July 2006 (105.6 mm SL) (DNA tag n°835) – MRAC A7-009 View Materials -P-1378, Inkisi River basin, Luguga River , village Kiyanika, Lower Congo ( DRC) (5°16’32.7’ S-15°12’36.3 ’E) Coll. S. Wamuini Lunkayilakio, 28 August 2006 (122.4 mm SL) (DNA tag n°706) – MRAC A7-009 View Materials -P-1382, Inkisi River basin, Nua River , village Mawunzi, Lower Congo ( DRC) (5°18’48.0’ S-15°16’31.9 ’E) Coll. S. Wamuini Lunkayilakio, 15 July 2006 (170.7 mm SL) (DNA tag n°838) – MRAC A9-014 View Materials -P-0004, Inkisi River basin, village Zongo, upstream of dam, Lower Congo ( DRC) (4°47’22.4’ S-14°54’35.5 ’E) Coll. S. Wamuini Lunkayilakio, 9 October 2008 (188.6 mm SL) (DNA tag n°1035) – MRAC A9-014 View Materials -P-0007, Inkisi River basin, Bongolo River , village Kinsende , Ndimba Kitadi, Lower Congo ( DRC) (5°23’10.7’ S-15°15’28.2 ’E) Coll. S. Wamuini Lunkayilakio, 23 August 2008 (133.1 mm SL) (DNA tag n°938) .