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

LABEOBARBUS NZADIMALAWU SP. NOV.

( FIGS 8A, 19; TABLES 1, 7, 8)

Labeobarbus sp. ‘Inkisi’ (Wamuini Lunkayilakio, 2010: 131)

Labeobarbus View in CoL sp. nov. ( Wamuini Lunkayilakio et al., 2010: 85; table 1)

Holotype: MRAC A7-009 View Materials -P-0815, Inkisi River basin, Bongolo River, Kinsende village , Lower Congo (5°23’10.7’S–15°15’25.2’E) Coll. S. Wamuini Lunkayilakio, 30 August 2006 (172.6 mm SL) (DNA tag n°713).

Paratypes: MRAC A6-007 View Materials -P-0519, Inkisi River basin, Kisantuvillage, LowerCongo (5°08’02.6’ S-15°03’51.5 ’E) Coll. Exp. Bas-Congo 2005, 6 October 2005 (123.8 mm SL) (DNA tag n°567) – MRAC A6-007 View Materials -P-0535, Inkisi River basin, Ngufu River , at the bridge between Luangu and Kavuaya village, Lower Congo (5°04’44.2’ S-15°07’51.0 ’E) Coll. Exp. Bas-Congo 9 October 2005 (202.9 mm SL) (DNA tag n°618) – MRAC A7-009 View Materials -P-0818, Inkisi River basin, Fidi River, Kiyenga village , Lower Congo (5°31’33.8’ S-15°16’41.0 ’E) Coll. S. Wamuini Lunkayilakio, 4 September 2006 (177.2 mm SL) (DNA tag n°735) – MRAC A7-009 View Materials -P-0821, Inkisi River basin, Nua River, Mawunzi village , Lower Congo (05°18’48.0’ S-15°16’31.9 ’E) Coll. S. Wamuini Lunkayilakio, 14 February 2007 (139.7 mm SL) (DNA tag n°780) – MRAC A7-009 View Materials -P-0822, Inkisi River basin, Kinsende village , Lower Congo (5° 23 ’ 33.8 ’ S- 15 ° 15 ’13.1 ’E) Coll. S. Wamuini Lunkayilakio, 31 August 2006 (204.1 mm SL) (DNA tag n°730) – MRAC A9-0014 View Materials -P-0375, Inkisi River basin, Nsanga village , downstream of the falls, Lower Congo (4°50’39.4’ S-14°57’27.5 ’E) Coll. S. Wamuini Lunkayilakio, 13 October 2008 (117.7 mm SL) (DNA tag n°1076) .

Differential diagnosis: Within the Congo basin L. nzadimalawu can be distinguished 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 its high number of lateral line scales, i.e. 35–41 (vs. less than 34); from L. leleupanus by its low number of lateral line scales, i.e. 37–41 (vs. 45–47); from L. tropidolepis and L. platyrhinus by its low number of scales between the lateral line and the dorsal and ventral midline, i.e. 4.5–6.5 and 5.5–6.5 (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 its low number of circumpeduncular scales as well, i.e. 12–16 (vs. 16–18); from L. robertsi by the absence of papillae on the anterior edge of the lower jaw (vs. with numerous well identifiable papillae); from L. pellegrini by the presence of two pair of well-developed barbels (vs. a single pair of minute posterior barbels in L. pellegrini ); from L. progenys by its non-prognathous lower jaw (vs. 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 for about half of its length, i.e. 42.8–57.7% dorsal-fin height [vs. transformed into a spine, clearly segmented only at its most distal end, i.e. less than 30.0% dorsal-fin height (data missing for the holotype of L. somereni as the segmented part of the dorsal spine is broken off)]; and from L. somereni , by its 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, L. nzadimalawu can be distinguished from both the other members of the Inkisi complex, L. nzadinkisi and the intermediate/hybrid specimens by the presence of a free mental lobe (vs. no mental lobe but instead a cornified Varicorhinus real cutting edge on the outer edge of the lower jaw in L. nzadinkisi and no or only a rudimentary or attached mental lobe in hybrid specimens). In addition, L. nzadimalawu can be distinguished from L. nzadinkisi by its narrow mouth width, 16.1–26.5% HL (vs. 26.8–50.5% HL); long head length, 23.0–26.4% SL (vs. 20.1–22.1% HL); short dorsal-fin base length, 12.1–16.0% SL (vs. 14.4–17.9% SL); and long prepectoral distance, 22.6– 26.0% SL (vs. 20.0–22.1% SL) ( Figs 13A, B, 14A, B). Finally, L. nzadimalawu 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 L. nzadimalawu 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 its higher number of lateral line scales, i.e. 35–41 (vs. less than 34); from L. aspius , L. lucius and L. progenys by its non-prognathous lower jaw (vs. lower jaw clearly prognathous); and from L. rocadasi by its 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. 42.8–57.7% dorsal-fin height (vs. last unbranched dorsal-fin ray transformed into a spine, clearly segmented only at its most distal end). Finally, L. nzadimalawu can be distinguished from Sanagia velifera by its high number of lateral line scales, i.e. 35–41 (vs. 22–24).

Within the adjacent Quanza ichthyofaunal province, L. nzadimalawu can be distinguished from L. ansorgii , L. gulielmi , L. jubbi , L. nanningsi , L. rhinophorus , L. rosae and L. roylii by its 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 its non-prognathous lower jaw (vs. lower jaw clearly prognathous); and from L. boulengeri [previously L. latirostris ( Boulenger, 1910) ], L. ensis , L. girardi , L. steindachneri , L. stenostoma and L. rocadasi by its 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. 42.8– 57.7% dorsal-fin height (vs. last unbranched dorsal-fin ray transformed into a spine, clearly segmented only at its most distal end).

Description: The holotype is illustrated in Figure 19 and Figure 8A for its mouth phenotype. Meristics and measurements are given in Tables 7 and 8, respectively. Labeobarbus nzadimalawu has a rather shallow body depth, a low dorsal-fin height, and a shallow and elongated caudal peduncle. It is a relatively small-sized Labeobarbus species with a maximum observed size of ± 213 mm SL.

Labeobarbus nzadimalawu has a typical Lab.-mouth phenotype ( Table 1) characterized by the presence of a free mental lobe of variable size ( Figs 8A, B, 19). Anterior and posterior pair of barbels always present and well-developed ( Figs 8A, B, 19). Never papillae on jaws, neither on upper nor on lower jaw. Some specimens have a nose appendage ( Fig. 8B). Lower jaw always clearly shorter than upper jaw.

Tubercles (see Fig. 20) are present on all (≥117.7 SL) except the smallest of the examined specimens (62.9 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 seasons, as one specimen collected in February (small dry season) and several ones collected from August to October (end of major dry season and beginning of the wet season) (see Wamuini Lunkayilakio, 2010) all have them. Usually, tubercles are present all over the snout, i.e. on the dorsum of snout and lateral sides of snout 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. A few larger specimens (139.7 and about ≥200.0 mm SL) have a small number of tubercles below eyes, level with the infraorbital bones up to the preopercular/opercular skin fold. Both specimens with a well-developed nose were largely devoid of tubercles on the dorsum of the snout, i.e. from behind the nose up to the level of the anterior edge of the nostrils. Finally, remainder of body without tubercles. Tubercles are easiest observable in a specimen with a large mental lobe and in another one with a nose appendage [ MRAC A9-0014-P-0372: 212.5 mm SL (19/08/2008); and MRAC A6-07-P-535: 202.9 mm SL (09/10/2005)].

Lateral line scales of the examined specimen ( Fig. 21) with sinuous and parallel, although sometimes somewhat converging, striae. Number of striae on the posterior edge of these scales between about 34 and 43.

The pharyngeal teeth number of the only dissected specimen is 2.3.5. (left) – 5.3.2. (right) with the first tooth of the inner row being absent on the right pharyngeal bone ( Fig. 22). Note that on the left pharyngeal bone there are two additional smaller teeth present median of the inner row; those are not firmly attached to the bone but rather loosely embedded in the surrounding soft tissue; one of them already well-developed, the other one is more like a dome-like cusp.

Coloration: Live specimens silvery to white-grey on head, lateral side and dorsal midline. Most proximal part of the scales, i.e. the scale pockets, dark grey to blackish and this especially for the scales above the lateral line. The remaining, more distal part of the surface of the scales, silvery, white-grey. Fins darker, greyish-blue, with their distal margins whitish or even translucent. Ventral side and lower lateral side of head and body, below the lateral line, often a yellowish hue. Base of pectoral and pelvic fins sometimes also yellowish.

In alcohol, proximal surface of scales generally blackish and this especially for the scales above the lateral line. Absent in some of the larger sized specimens examined ( MRAC A7 -009- P- 1141: 210 mm SL; MRAC A9-14-P-0372: 213 mm SL), while persistent in others ( MRAC A6-07-P-0535: 203 mm SL; MRAC A7-009-P-0822: 204 mm SL). Fins generally light brown-whitish, although some parts might be blackish. The fin rays themselves yellowish-white. With increasing size, fins more and more blackish, although the rays remain light brown yellowish-white.

Distribution: Species endemic to the Inkisi River, Lower Congo River basin above the Zongo Falls ( Fig. 23). Currently only known from the DRC part of the basin.

Etymology: Before the Christian missionaries arrived, the Inkisi River was locally referred to as the ‘ Nzadi malawu ’ in Kikongo (Kintandu/Kindibu dialects), which means ‘the river that brings good luck’ (i.e. the porte-bonheur River in French). The part of the river towards the northern border of Angola still bears this name. Species name referring to this ancient name of the river basin to which it seems endemic. Species name to be treated as a noun in apposition ( ICZN, 1999: Articles 31.2.1. and 34.2.1), making its gender ending unchangeable.

Ecology: A small-scale ecological study of ten fishing stations on the Inkisi basin (Wamuini Lunkayilakio, 2010: tables 4.2, 4.3 4.5, 4.8; Wamuini Lunkayilakio et al., 2010: figs 1, 3) revealed L. nzadimalawu , the Lab.-mouth phenotype species, to be most abundant at Kinsendi, downstream and upstream of the Sanga Dam, where the Inkisi River is wide. In contrast, L. nzadinkisi , the Var.-mouth phenotype species, was less abundant or even absent at those stations. For more details on L. nzadinkisi , see below. Although preliminary, these data seem to reveal important differences in habitat preferences between both species but, unfortunately, no data are available for the intermediate-mouth phenotype specimens or hybrids, which were not included in these analyses.

Other specimens examined: MRAC A7-009 View Materials -P-1141, Inkisi River basin, Nsanga village, downstream of dam, Lower Congo (4°50’39.4’ S-14°57’27.5 ’E) Coll. S. Wamuini Lunkayilakio, 23 September 2006 (210.4 mm SL) (DNA tag n°891) . – MRAC A9-0014 View Materials -P-0372, Inkisi River basin, Boko village , Sawu dia Boko, Bas Congo (5°19’13.9’ S-15°12’14.0 ’E) Coll. S. Wamuini Lunkayilakio, 19 August 2008 (212.5 mm SL) (DNA tag n°930) . – MRAC A9-0014 View Materials -P-0376-0377., Inkisi River basin, Nsanga village, slope of the dam, Lower Congo (4°50’33.8’ S-14°57’34.9 ’E) Coll. S. Wamuini Lunkayilakio, 16 October 2008 (62.9– 130.2 mm SL) (DNA tag n°1113–1114) .