Orthochromis mporokoso, Schedel & Vreven & Manda & Abwe & Manda & Schliewen, 2018

Schedel, Frederic Dieter Benedikt, Vreven, Emmanuel J. W. M. N., Manda, Bauchet Katemo, Abwe, Emmanuel, Manda, Auguste Chocha & Schliewen, Ulrich Kurt, 2018, Description of five new rheophilic Orthochromis species (Teleostei: Cichlidae) from the Upper Congo drainage in Zambia and the Democratic Republic of the Congo, Zootaxa 4461 (3), pp. 301-349 : 308-313

Orthochromis mporokoso sp. nov.

Orthochromis sp. “Kasinsha”— Schedel et al. 2014

Holotype. ZSM 46840 (59.04 mm SL, ex ZSM 41443), Zambia, Kasinsha stream north of Luwinga affluent to Lake Mweru (-9.4894/30.5769).

Paratypes. ZSM 41429 (9, 34.0– 74.48 mm SL), Zambia, Mutoloshi stream above Kapuma Falls at Mporokoso on road Mukunsa-Luwinga (-9.3889/30.0956). — ZSM 41443 (4, 40.9–63.2 mm SL), collected with holotype .— MRAC 2018-006 -P-0009-0011 (3, 48.7–51.9 mm SL) Zambia, Mutoloshi stream above Kapuma Falls at Mporokoso on road Mukunsa-Luwinga (-9.3889/30.0956).

Additional material. ZSM 46841 (1, ex 41429, 54.28 mm SL; specimen with deformed jaws), Zambia, Mutoloshi stream above Kapuma Falls at Mporokoso on road Mukunsa-Luwinga (-9.3889/30.0956).

Differential diagnosis. Orthochromis mporokoso can be readily distinguished from all species currently placed in Orthochromis species of the genus Orthochromis and O. sp. “Igamba” from the Malagarasi drainage system by having more scale rows on cheek (2–4 vs. 0–1). Furthermore, O. mporokoso can be distinguished from O. kasuluensis , O. mosoensis , and O. rugufensis by having more scales on operculum (3–4 vs. 0–2); from O. kasuluensis by having fewer total vertebrae (30 vs. 31–32); from O. rugufuensis by fewer dorsal-fin spines (16–17 vs. 19); from O. mazimeroensis by more horizontal line scales (29–30 vs. 26–28), more abdominal vertebrae (14 vs. 12–13) and more total vertebrae (30 vs. 28–29); from O. rubrolabialis and O. uvinzae by fewer dorsal-fin spines (16–17 vs. 18–20); it has more total gill rakers than O. rubrolabialis (10–12 vs. 8–9) and differs in position of pterygiophore supporting last dorsal-fin spine (vertebral count: 16 vs. 17–18). It differs from O. uvinzae additionally by having fewer scales between upper lateral line and dorsal-fin origin (4–5 vs. 6–8), fewer abdominal vertebrae (14 vs. 15–16), fewer total vertebrae (30 vs. 31–33), position of pterygiophore supporting last dorsal-fin spine (vertebral count: 16 vs. 18–19), position of pterygiophore supporting last anal-fin spine (vertebral count: 14- 15 vs. 16–17); from O. luongoensis and O. torrenticola by having fewer caudal vertebrae (16 vs. 17–18) and total vertebrae (30 vs. 31–33); from O. kalungwishiensis by having fewer total vertebrae (30 vs. 31–33) and fewer horizontal line scales (29–30 vs. 31–32); from O. torrenticola additionally by having fewer anal-fin spines (3 vs. 4) and position of pterygiophore supporting last anal-fin spine (vertebral count: 14–15 vs. 16–17). It can be distinguished from O. stormsi and O. polyacanthus by having fewer scales between upper lateral line and dorsal-fin origin (4–5 vs. 6–9). In addition, it is distinguished from O. stormsi by having more horizontal line scales (29–30 vs. 26–28), more total vertebrae (30 vs. 28–29) and fewer total gill rakers (10–12 vs. 13–15); from O. polyacanthus by having more series of scales on cheek (2–4 vs. 0), fewer dorsal-fin spines (16–17 vs. 18–20) and in position of pterygiophore supporting last dorsal-fin spine (vertebral count: 16 vs. 17–18) as in position of pterygiophore supporting last anal-fin spine (vertebral count: 14–15 vs. 16–17). Meristic values of O. mporokoso overlap with those of O. machadoi , but it can be readily distinguished by having more vertical bars on flanks (13–15 vs. 9–10), which moreover extend mainly ventrally; those of O. machadoi extend mainly dorsally. In addition, it is distinguished in head mask pattern, i.e. V -shape nostril stripe in O. mporokoso vs. straight nostril stripe in O. machadoi ; cheek stripe present vs. absent in O. machadoi . It differs from Schwetzochromis neodon by having more circumpeduncular scales (16 vs. 12), fewer inner series of teeth (1–3 vs. 4–6) and fewer dorsal-fin rays (9–10 vs. 11–12). It differs from H. bakongo and H. moeruensis by having more horizontal line scales (29–30 vs. 26–28), more caudal vertebrae (16 vs. 12–15) and more total vertebrae (30 vs. 26–29). Additionally, it is distinguished from H. moeruensis by having more upper lateral line scales (21–23 vs. 19–20); from H. bakongo by having more dorsal-fin spines (16–17 vs. 14–15) and in position of pterygiophore supporting last dorsal-fin spine (vertebral count: 16 vs. 13–14); and from H. snoeksi it is distinguished by having more abdominal vertebrae (14 vs. 13), fewer caudal vertebrae (16 vs. 17), more anal-fin rays (7–9 vs. 5–6), more total gill rakers (10–12 vs. 9), and in position of pterygiophore supporting last dorsal-fin spine (vertebral count: 16 vs. 15) and position pterygiophore supporting last anal-fin spine (vertebral count: 14–15 vs. 13). Meristic values of O. mporokoso overlap with those of H. vanheusdeni , but it lacks eggspots, has a nostril stripe (vs. absent in H. vanheusdeni ), exhibits a cheek stripe (vs. absent in H. vanheusdeni ), and has higher number of vertical bars on flank (13–15 vs. 6–7). It differs from herein newly described species O. kimpala by having fewer scales between upper lateral line and dorsal-fin origin (4–5 vs. 6–7); from O. indermauri by having more series of scales on the cheek (2–4 vs. 0–1), more caudal vertebrae (16 vs. 14–15), and more total vertebrae (30 vs. 28–29). Meristic values of O. mporokoso overlap with those of O. katumbii but former differs by having more vertical bars on flank (13–15 vs. 7–9) and by head mask pattern (i.e.: cheek stripe present vs. absent in O. katumbii ). Meristic values of O. mporokoso overlap with those of O. gecki but former is distinguished by having much wider interorbital (15.3–19.5 vs. 9.6–12.9 % HL) and by lacking eggspots on anal fin vs. present in O. gecki .

Description. Morphometric measurements and meristic characters are based on 17 type specimens and one additional deformed specimen. Values and their ranges are presented in Table 2. For general appearance see figure 3. Maximum length of wild caught specimens 74.5 mm SL. Moderately slender species with maximum body depth (24.7–29.3 % SL) at level of dorsal-fin origin, slowly decreasing towards caudal peduncle. Caudal peduncle rather elongated and moderately deep (ratio of caudal-peduncle length to depth: 1.5–2.3). Head length almost one third of standard length. Dorsal head profile slightly curved without prominent nuchal gibbosity. Eye diameter larger than interorbital width. Jaws isognathous or slightly retrognathous. Posterior tip of maxilla not reaching anterior margin of orbit but ending slightly before. Lips not noticeably enlarged or thickened. Two separate lateral lines.

Squamation. Flank above and below lateral lines covered with comparatively large ctenoid to cycloid scales, especially in large specimens only few scales of ctenoid appearance. Anterior dorsal and ventral flank area covered by cycloid scales. Belly with comparatively small cycloid scales. Chest covered with even smaller cycloid scales compared to belly squamation; chest to flank transition with larger cycloid scales. Snout scaleless up to anterior margin of orbit. Interorbital, nape, and occipital region with medium sized cycloid scales. Cheeks covered by small cycloid scales; 2–4 scale rows on cheek. Cycloid scales on operculum of variable size (small to medium sized) and shape (ovoid to circular); opercular blotch partially covered by medium sized scales, but posterior margin scaleless. 3–4 scales on horizontal line starting from edge of postero-dorsal angle of operculum to anterior edge of operculum.

Upper lateral line scales 21–23 and lower lateral line 9–11. Horizontal line scales 29–30. Caudal fin with 0–2 pored scales. Upper and lower lateral lines separated by two scales. 3–5 scales between upper lateral line and dorsal-fin origin. Anterior part of caudal fin covered with 4–5 vertical columns of small cycloid scales with median scales slightly larger; scaled area of caudal fin extended posteriorly especially at upper and lower area with minute, interradial scales (approximately up to one third of caudal fin). Sixteen scales around caudal peduncle.

Jaws and dentition. Anterior bicuspid teeth of outer row in both upper and lower jaw large and closely set; posterior teeth becoming almost subequally bicuspid; towards corner of mouth teeth smaller and less closely set, may become unicuspid or weakly bicuspid especially in upper jaw. Individual bicuspid teeth with minimally expanded brownish crown, cusps (major cusp with almost horizontal edge) uncompressed and moderately widely set, and neck moderately slender to stout. Outer row upper jaw with 31–44 teeth and outer row lower jaw with 23– 33 teeth (specimens: 34.0–59.0 mm SL). Larger specimens generally with more teeth. Two to three (rarely one) inner upper and lower jaw tooth rows with small tricuspid teeth. Lower pharyngeal bone ( Fig. 3 ) of single dissected paratype (ZSM 41429, 59.8 mm SL) about 1.3 times wider than long with short anterior keel about 0.4 times length dentigerous area. Dentigerous area of lower pharyngeal bone about 1.5 times wider than long, with 10+10 teeth along posterior margin and 7–8 teeth along midline. Anterior pharyngeal teeth (towards keel) bevelled and slender; those of posterior row larger than anterior ones, bevelled (bicuspid; well-developed major and minor cusp). Largest teeth medially situated in posterior row. Teeth along midline slightly larger than more lateral ones.

Gill rakers. Total gill raker count 10–12, with two epibranchial, one angle, and 7–9 ceratobranchial gill rakers. Most anterior ceratobranchial gill rakers very small, increasing in size towards cartilaginous plug (angle). Gill raker in angle slightly shorter than longest ceratobranchial raker and epibranchial gill rakers further decreasing in size.

Fins. Dorsal fin with 16–17 spines and with 9–10 rays. First dorsal-fin spine always shortest. Dorsal-fin base length between 50.2–55.6 % SL. Posterior end of dorsal-fin rays ending slightly before or at caudal fin base; posterior tip of anal fin ending slightly before caudal-fin base. Caudal-fin outline subtruncate and fin composed of 26–29 rays (16 principal caudal-fin rays and 10–13 procurrent caudal-fin rays). Anal fin with three spines (third spine longest) and 7–9 rays. Anal-fin base length between 15.2–20.1 % SL. Pectoral fin with 15–16 rays. Pectoralfin length between 21.6–25.7 % SL, longest pectoral ray not reaching level of anus. First upper and lower pectoralfin rays very short to short. Pelvic fin with first spine thickly covered with skin and five rays. Pelvic-fin base slightly posterior of pectoral-fin base. Pelvic fin slightly longer than pectoral fin; longest pelvic-fin ray almost reaching anus (ending approximately 0.5–2 flank scale widths before).

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Vertebrae and caudal fin skeleton. ( Fig. 3 ). A total of 30 vertebrae (excluding urostyle element), with 14 abdominal and 16 caudal vertebrae. The pterygiophore supporting last dorsal-fin spine is inserted between neural spines of 16th and 17th vertebra (counted from anterior to posterior). Pterygiophore supporting last anal-fin spine is inserted between haemal spines of 15th and 16th vertebra, rarely between ribs of 14th and haemal spine of 15th vertebra (N=2). Single predorsal bone (=supraneural bone) present. Hypurals 1 and 2 as well as hypurals 3 and 4 always fused into single seamless units.

Colouration in life (based on field photographs of adult specimens). ( Fig. 3 ) Body ground colouration pale

brown to light grey; anterior flank with yellow to golden reticulated pattern which becomes less prominent at level of anus and stops at level of caudal peduncle. Dark grey to brownish, interrupted midlateral band from operculum to just posterior caudal fin base, ending in mostly visible blotch; intensity midlateral band varies depending on mood often hardly visible. Midlateral band crossed by 13–15 vertical bars, which extend mainly ventrally, hardly recognizable except for more distinct first 4–5 anterior bars. In some specimens dorsum with irregular dark brown areas, which sometimes connect with midlateral band. Scales on, above and below midlateral band until level of anus with blackish-blue to greyish-blue centres. Dorsum and caudal peduncle pale brown to light grey; chest and belly light beige. Dorsal head surface pale brown to light grey; snout and cheek beige, ventrally brighter. Branchiostegal membrane light beige. Operculum beige to yellowish, sometimes with metallic turquoise speckles, a black opercular spot connecting with anterior extension of midlateral band (interrupted at level of preoperculum) ending in well-pigmented blotch slightly anterior of eye. Another dark grey to brownish element of variable form on ventral corner of operculum. Cheek with small, dark grey to brownish vertical stripe of variable shape and intensity, extending to slightly below eye (not reaching eye). Dark grey to brownish lachrymal stripe ending at posterior end upper lip. Very thin, dark grey to brownish nostril stripe (sometimes interrupted) V -shaped, extending between nostrils. Thin, dark grey to brownish interorbital stripe present; no distinct supraorbital stripe, but area just above eye somewhat darker than remaining dorsal head region. Upper and lower lip beige to pale brown, lower margin of upper lip greyish (darker coloured), lower lip lighter than upper. Dorsal-fin membrane transparent with orange maculae, sometimes arranged in inclined rows; maculae bordered with orange and outlined with black, especially in spinous part of fin. Anal fin transparent to yellow, towards margin becoming more intensively coloured, no maculae or eggspots present. Caudal fin yellowish to greyish with two or three rows of small yelloworange maculae near fin base. Outer caudal-fin rays with black margin. Pectoral and pelvic fins transparent but rays yellowish to greyish.

Juvenile colouration in life. No information about juvenile colouration available.

Colouration in alcohol. Colouration and melanin patterns similar to live specimens, but due the preservation procedure of specimens, i.e., first formalin fixation, transfer to 75 % EtOH etc., specimens tend to lose original colouration (especially melanin patterns more intense than in live specimens). Overall body ground colouration light brownish; dorsum darker than flank below midlateral band. Chest and belly beige to yellowish-beige. Branchiostegal membrane beige, along operculum and ventrally becoming reddish brown. Dorsal head surface and dorsum brownish, ethmoidal region greyish-brown. Upper lip beige to light greyish anteriorly, lower lip beige. Cheek beige to pale brownish; vertical stripe on cheek faint. Operculum beige to pale brown greyish and with opercular spot as described above (brownish element on operculum less clearly defined than in live specimens and covering almost entire operculum). Head mask brownish. Midlateral band and vertical bars brownish and more intense (especially posterior bars). Dorsal fin whitish to light greyish and margins outlined in black; maculae visible but less intense and greyish. Anal fin whitish to beige; margins blackish outlined. Caudal fin light whitish to beige; margins blackish outlined, small greyish speckles visible on membrane. Pectoral fin and pelvic fin whitish to light grey.

Distribution and biology. Orthochromis mporokoso is known from two clear water streams in the vicinity of Mporokoso town. Kasinsha stream (holotype locality, Fig. 1 ) is about five meters wide with a rocky bottom and on average 50–100 cm deep ( Fig. 8 ).

The water temperature at the type locality was 19.5 °C (15.07.2011, late afternoon) and had a pH of 6.7; at the second sampling locality (Mutoloshi River at Kapuma Falls) a temperature of 19.3 °C (15.07.2011) and a pH of 7.3 was recorded (pers. comm. H. van Heusden 2017). Orthochromis mporokoso is a benthic-rheophilic species.

Etymology. The species name mporokoso is derived from Mporokoso, a town in the Northern Province ( Zambia) near the type locality of the species. A noun in apposition.

Figures

FIGURE 1. Map of south-eastern DRC and Northern Zambia, with indications of the type localities of the known Orthochromis species of the Upper Congo drainage system and new Orthochromis species. Star = type locality, circle = either paratype locality or sample locality of comparative specimens. Species indicated by colour: O. mporokoso sp. nov. (light blue); O. katumbii sp. nov. (purple); O. kimpala sp. nov. (orange); O. gecki sp. nov. (deep orange); O. indermauri sp. nov. (deep blue); O. kalungwishiensis (dark red); O. luongoensis (green). O polyacanthus (brown) and O. torrenticola (yellow). Major citys are depicted in black. Map is based on shapefiles obtained from DIVA-GIS (http://www.diva-gis.org/Data).

FIGURE 3. Orthochromis mporokoso sp. nov. A. probably the holotype, alive. Dorsal, anal and caudal fin background coloration is uniform semitransparent and might be lightly yellowish to greyish, i.e. not as in picture (human fingers holding the specimen in photo tank gave artificial beige color to semitransparent fins). B. Holotype (ZSM 46840), 59.0 mm SL; Zambia, Kasinsha stream C. radiograph of holotype D. lower pharyngeal bone (specimen with 59.8 mm SL; ZSM 41429) E. Overview of arrangement and morphology of oral jaw teeth (specimen with 74.5 mm SL; ZSM 41429).

FIGURE 8. Type localities of the five newly described species A. Type locality of Orthochromis mporokoso, Kasinsha stream (July 2011, Hans van Heusden) B. Type locality of Orthochromis katumbii, Kiswishi River (2015, VLIR expedition) C. Type locality of Orthochromis gecki, Lubudi River (July 2017, Katanga 2016 Expedition) D. Type locality of Orthochromis kimpala, Kalule North River near bridge on the road Makulakulu-Lubudi (2012, PRODEPAAK expedition) E. Type locality of Orthochromis indermauri, Lufubu River at Chomba village (August 2015, photo F. Schedel).