Barbus, Stiassny, Melanie L. J., Liyandja, Tobit L. D. & Iyaba, Raoul J. C. Monsembula, 2016

Stiassny, Melanie L. J., Liyandja, Tobit L. D. & Iyaba, Raoul J. C. Monsembula, 2016, A new small barb (Cyprininae: Smiliogastrini) from the N’sele and Mayi Ndombe rivers in the lower reaches of the middle Congo basin (Democratic Republic of Congo, Central Africa), American Museum Novitates 2016 (3848), pp. 1-16 : 5-12

“ Barbus ” validus, new species

Figures 2–6 ; table 2

HOLOTYPE: AMNH 259318 , female, 73.9 mm SL, Democratic Republic of Congo, Kinshasa Province , Mayi Ndombe River at bridge (04° 16′ 39.9″ S, 015° 58′ 06.1″ E), T. Liyandja, 9 September 2011.

PARATYPES: AMNH 254600 , 61.8 mm SL, Democratic Republic of Congo, Kinshasa Province , N’Sele River, small right bank stream flowing into main channel (04° 17′ 59.6″ S, 015° 41′ 09.2″ E) , R.J.C. Monsembula Iyaba et al., 07 August 2011 . — AMNH 254601 , 56.3 mm SL, same data as AMNH 254600 . — AMNH 259299 , 93.2 mm SL, same locality as holotype, 7 September 2011 . — AMNH 259274 , 80.4 mm SL, same locality as holotype, 01 July 2011 . — MCZ 171830 , 78.3 mm SL, same locality as holotype, 01 July 2011 . — AMNH 263755 , 2 specimens, 73.0– 91.1 mm SL, same data as holotype . — AMNH 259310 , 3 specimens, 77.5–90.1 mm SL, same locality as holotype, 8 March 2011 . — BMNH 2015.8 .17.1, 76.0 mm SL, same locality as holotype, 8 March 2011 . — AMNH 259315 , 2 specimens, 79.4–93.8 mm SL, same locality as holotype, 22 August 2011 . — ZSM 43946, 82.1 mm SL, same locality as holotype, 22 August 2011 . — AMNH 258019 , 4 specimens, 49.5–63.2 mm SL, Democratic Republic of Congo, Mai-Ndombe Province , Mayi Ndombe River, main channel just downstream of second rapid (03° 55′ 51.4″ S, 015° 58′ 06.1″ E) , T. Liyandja, 01 May 2011 . — AMNH 258076 , 5 specimens, 49.6–94.8 mm SL, same locality as holotype, 30 June 2011 . — MRAC B5-025 -P-0001-0002, 2 specimens, 58.2–82.2 mm SL, same locality as holotype, 30 June 2011 . — AMNH 259240 , 6 specimens, 56.1–85.2 mm SL, 2 C&S, Democratic Republic of Congo, Mai-Ndombe Province , Mayi Ndombe River, main channel (04° 18′ 22.2″ S, 015° 59′ 20.8″ E) , T. Liyandja et al., 01 July 2011 . — AMNH 258938 , 2 C&S, 49.1–52.8 mm SL, Democratic Republic of Congo, Kinshasa Province , Lumene River , ICCN base (04° 25′ 09.7″ S, 016° 02′ 50.3″ E) , T. Liyandja et al., 05 March 2011 . — AMNH 259332 , 71.5 mm SL, Democratic Republic of Congo, Kinshasa Province , Mayi Ndombe River, Butu Bunkiene (04° 17′ 45.2″ S, 015° 58′ 18.8″ E) , T. Liyandja et al., 09 September 2011 .

OTHER MATERIAL EXAMINED: AMNH 263756 , 10 specimens, 4 nonformalin fixed, same locality as holotype, 30 June 2011 . — AMNH 263757 , 8 specimens, 2 nonformalin fixed, Democratic Republic of Congo, Mai-Ndombe Province , Mayi N’dombe River, main channel, 04° 18′ 22.2″ S, 015° 59′ 20.8″ E, Coll . T. Liyandja et al., 01 July 2011 (4 as gift to University of Kinshasa teaching collection) . — AMNH 257942 , 4 specimens, Democratic Republic of Congo, Kinshasa Province , River Lumene ( ICCN base) (04° 25′ 09.7″ S, 016° 02′ 50.3″ E) , T. Liyandja et al., 05 March 2011 . — AMNH 258062 , 11 specimens, 4 nonformalin fixed, Democratic Republic of Congo, Kinshasa Province , Mayi Ndombe River, main channel at bridge (04° 16′ 39.9″ S, 015° 58′ 06.1″ E) , T. Liyandja et al., 29 June 2011 . — AMNH 263758 , 3 specimens, same locality as holotype, 22 August 2011 . — AMNH 263759 , 3 specimens, nonformalin fixed, Democratic Republic of Congo, Mai-Ndombe Province , Mayi Ndombe River, main channel just downstream of second rapid (03° 55′ 51.4″ S, 015° 58′ 06.1″ E) , T. Liyandja, 01 May 2011 . — AMNH 258041 , same locality as AMNH 258019, 22 May 2011 . — AMNH 259318 , same data as holotype . — AMNH 259236 , 4 specimens, nonformalin fixed, Democratic Republic of Congo, Mai- Ndombe Province , Mayi Ndombe River , T. Liyandja, 30 June 2011 .

DIFFERENTIAL DIAGNOSIS: “ Barbus ” validus is distinguished from all other African smiliogastrin species by the following features that, in combination, uniquely diagnose the species: scales in midlateral series not enlarged relative to impinging rows above and below; barbels well developed, maxillary pair extending beyond level of mideye, mandibular pair reaching level of midopercle; numerous conical tubercles over snout and cheek, and dorsum of head; small circular occipital fontanel often present and located medially at parietal suture; gill rakers well developed, 8 or 9 on hypo- and ceratobranchial elements of the first arch; last unbranched dorsal-fin ray weakly ossified, flexible, and lacking serrations along posterior edge; dorsal fin creamy white proximally, distal half to two thirds darkly pigmented.

DESCRIPTION: A robust, deep-bodied “ Barbus ” attaining a maximum-recorded size of 95.8 mm SL (mature male, AMNH 258076 ), with general appearance as in figure 2. Proportional measurements and meristic counts for holotype and 34 paratypes given in table 2. Head relatively small, eyes large, mouth subinferior. Barbels robust and prominent, maxillary pair extending beyond level of mideye, mandibular pair reaching level of midopercle. Mature males with rows of large conical tubercles over snout, and numerous smaller tubercles scattered over dorsum of head (fig. 3A, C). Tubercles present, generally smaller and less prominent in females and juveniles. Small, circular, occipital fontanel usually present, located in midline at parietal suture, contained entirely within parietals (compare fig. 4A and 4B, C, see discussion). Five infraorbitals ( IO): IO1 deepest of series, IO2–4 with infraorbital canal portion of bone occupying dorsal half of each element, IO3 longest of series, twice length of IO1 , IO5 reduced to canal (fig. 3B). Scales radially striated, 22–25 in lateral line (+2–3 scales over caudal fin base), 3.5/1/2.5 body rows, 11–12 circumpeduncular rows, and 7–8 predorsal rows. Lateral line complete, scales not enlarged relative to those along impinging rows above and below .

Dorsal fin iii.8, positioned midway between snout and caudal-fin base, origin anterior to pelvic-fin insertion. Last unbranched ray long and flexible, lacking serrations on posterior border. Anal fin iii.5, forked caudal fin, 9 + 10 principal rays, 7–8 + 8–10 procurrent rays. Pelvic fin, 8 rays (i.7), pectoral fin, 15–16 rays (i.14–15).

Gill rakers well developed, 8–9 arrayed along hypo- and ceratobranchial of first arch, one smaller epibranchial raker usually present.

Total vertebrae 34–35, 18–20 abdominal, 15–17 caudal (holotype: 19 + 16). Thirteen or 14 pleural ribs, 4–5 supraneurals located between neural spines of vertebral centra 4–8. First dorsal-fin pterygiophore between neural spines of vertebral centra 9–10, and first anal-fin pterygiophore directed at hemal spine of vertebral centra 19 or 20. Caudal-fin rays supported by neural and hemal spines of preural centra 2–3. Pleurostyle, single epural, parhypural + seven hypural elements present.

Coloration in preservation (fig. 2A); base body coloration yellowish brown, darker dorsally, becoming pale ventrally and over belly, cheek, and jaws. Snout and dorsum of head, dark grayish brown. Faint trace of a cleithral stripe present in large individuals but often obscured by opercular margin. Body scales with a dark chevron-shaped marking along proximal edge, strongest dorsally and particularly along lateral line, less clearly marked ventrally. Dorsal fin creamy white proximally, distal half to two thirds darkly pigmented. Pectoral and pelvic fins smoky gray, strongly so in larger males. Scales over region of caudal flexion somewhat darker than preceding scales and forming a trace of a caudal bar. Base of caudal fin pale gray proximally, hyaline distally. Coloration immediately post mortem (fig. 2B) similar to that in preservation but overlain with a silvery reflectance and pale rose flush on ventrum. Rosy flush particularly evident in large males where it extends onto pectoral, pelvic, and anal fins.

GUT MORPHOLOGY AND DIET: Digestive tract short; esophagus leads to large, elongate, thick-walled stomach. Intestine exits directly from distal end of stomach, making a single rostrocaudad loop before descending to anus (fig. 2C). Total length of tract (unraveled but not stretched) ca. 80%–90% SL. Review of gut contents (preserved specimens) indicates that “ B. ” validus is omnivorous and opportunistic. Most gut contents contained disarticulated insect remains, including many tricopteran larvae and fragmented sand cases, numerous chironomid larval head cases and bodies, and various unidentifiable insect remains. In addition, woody debris, seeds, and macerated grasses, and few terrestrial arthropod remains of spiders and ants are also present, suggesting the species is opportunistically harvesting both aquatic and exogenous resources.

SEXUAL DIMORPHISM AND REPRODUCTION: Adult male specimens are generally larger than females (largest male, 95.8 mm SL, AMNH 258076; largest female, 88.9 mm SL, AMNH 259310) and, in addition to possessing larger conical tubercles over the snout, they tend also to be deeper bodied than females of similar size (fig. 5). Specimens collected in June, July, and August showed no sign of maturation of ovaries or testes. Most large individuals collected in March had enlarged testes or ovaries filled with numerous small, round eggs suggesting that peak breeding occurs at that time.

DISTRIBUTION: Currently known only from the N’sele and Mayi Ndombe Rivers (fig. 6). Further collecting in additional tributaries of the Middle Congo and Kwango River (Kasai drainage) will likely extend this distributional range. We note, however, that no specimens of the species are present in collections from the main channel of the Congo River either above or below Pool Malebo.

ETYMOLOGY: Specific name, validus, from the Latin meaning strong or powerful, in reference to the robust appearance of the species.

COMPARATIVE MATERIALS EXAMINED: “ Barbus ” humeralis: AMNH 6137 (holotype of Barbus dolichosoma ), 52.2 mm SL, Democratic Republic of Congo, Tshopo Province, Avakubi. —BMNH 1901.12.26, syntype, 64.8 mm SL, Democratic Republic of Congo, Nord-Ubangi Province, Yembe River at Banzyville. —AMNH 253265, 51.5 mm SL, Democratic Republic of Congo, Kasai Central Province, Miao River, tributary of Lulua River (05° 56′ 23.0″ S, 022° 13′ 17.7″ E). — AMNH 247409, 38.5–49.1 mm SL, 2C&S, Democratic Republic of Congo, Kasai Central Province, Katende, Lulua River (06° 00′ 16.2″ S, 022° 23′ 25.8″ E). — AMNH 253143, 51.2 mm SL, Democratic Republic of Congo, Kasai Central Province, Tshiyoyi, Lulua River. — AMNH 247497, 51.4 mm SL, Democratic Republic of Congo, Lulua Province, Ntumba Shambuyi (05° 43′ 59.4″ S, 023° 19′ 06.0″ E). — AMNH 252779, 48.5 mm SL, Democratic Republic of Congo, Kasai Occidental Province, Kampaya, Lulua River (06° 25′ 32.9″ S, 022° 24′ 58.98″ E). — AMNH 247409, 2 cleared and stained specimens, 45.9–48.2 mm SL, Democratic Republic of Congo, Lulua Province, Katende, Lulua River (06° 00′ 16.2″ S, 022° 23′ 25.8″ E).

“ Barbus ” miolepis: AMNH 254599, 56.0 mm SL, Democratic Republic of Congo, Kinshasa Province, small rightbank stream flowing into main channel of N’sele River (04° 17′ 59.6″ S, 015° 41′ 09.2″ E) . — AMNH 255139 , 2 specimens, 48.5–56.8 mm SL, Democratic Republic of Congo, Mai-Ndombe Province , Mayi Ndombe River, Nganda Banga Nzambe above second rapid (03° 56′ 54.5″ S, 015° 59′ 20.3″ E) . — AMNH 250765 , 2 C&S, 56.1–57.8 mm SL, Democratic Republic of Congo, Kinshasa Province , small stream flowing into N’sele River (04° 26′ 41.0″ S, 015° 41′ 00.4″ E) .

“ Barbus ” vanderysti: AMNH 257140, 4 specimens, 2 C&S, 48.5–56.4 mm SL, Democratic Republic of Congo, Kinshasa Province, River Binkukiti, N’Sele River drainage (05° 12′ 43.1″ S, 015° 34′ 21.8″ E) . — AMNH 255251 , 12 specimens, 46.4–62.0 mm SL, Democratic Republic of Congo, Kinshasa Province , River Nkengi, N’Sele River drainage (05° 14′ 21.1″ S, 015° 32′ 49.1″ E) . — AMNH 255259 , 5 specimens, 43.4–59.5 mm SL, Democratic Republic of Congo, Kinshasa Province , River Zodi, N’Sele River drainage (05° 12′ 47.9″ S, 015° 34′ 24.8″ E) .

Clypeobarbus matthesi: AMNH 256172, 5 specimens, 43.1–65.0 mm SL, Democratic Republic of Congo, Kwilu Province , Kwilu River (05° 20′ 54.2″ S, 018° 56′ 16.0″ E). — AMNH 250565 , 4 specimens, 48.2–58.6 mm SL, Democratic Republic of Congo, Kinshasa Province , N’sele River, below rapids at Kisangani Village, 04° 21′ 31.9″ S, 015° 42′ 54.1″ E. — AMNH 258000 , 7 specimens, 2 C&S, 49.5–53.0, Democratic Republic of Congo, Kinshasa Province , Mayi Ndombe River at Mayi Ndombe Village . — AMNH 240447 , 81.7 mm SL, Democratic Republic of Congo, Tshuapa Province , Salonga National Park , Nkombe-Dunda, Luilaka River (02° 40.289′ S, 021° 43.259′ E) .

Clypeobarbus pleuropholis: AMNH 250741, 8 specimens, 34.4–47.8 mm SL, Democratic Republic of Congo, Kinshasa Province, Right bank N’Sele River, just below rapids (04° 21′ 31.9″ S, 015° 42′ 54.1″ E) . — AMNH 237086 , 5 C&S, 34.3–39.9 mm SL, Republic of Congo, Main channel of Congo River at confluence of Djoue River (05° 17′ 32.4″ S, 018° 56′ 29.6″ E) . — AMNH 254854 , 5 specimens, 36.8–48.5 mm SL, Democratic Republic of Congo, Kinshasa Province, main channel Congo River en route to Mayi Ndombe River (04° 01′ 31.4″ S, 015° 36′ 37.1″ E) .

Figures

FIGURE 2. “Barbus” validus, new species: A, AMNH 259318, holotype (female) and AMNH 254600, paratype (male) in preservation; B, female and male immediately postmortem; C, digestive tract (slightly unraveled for clearer depiction of morphology), after removal of liver and adherent tissues (not to scale). Scale bars = 1 cm.

FIGURE 3. “Barbus” validus, new species: A, head in lateral view; B, isolated infraorbital series; C, head in dorsal view. White outlines indicate the location of tubercles.

FIGURE 4. Neurocrania in dorsal view: A, “Barbus” validus, AMNH 258938; B, “Barbus” humeralis, AMNH 247409; C, “Barbus” miolepis, AMNH 250765. Arrows indicate location of occipital foramina.

FIGURE 5. Principle components (PC) 1 and 2 displaying variation in body shape for mature male (stars) and female (circles) specimens of “Barbus” validus. Visualization of shape variation is provided as warped grids of (A) minimum and (B) maximum PC 1 values relative to mean shape.

FIGURE 6. A, Distributional range of “Barbus” validus: yellow stars indicate collection sites and blue star indicates collection locality of holotype; B, typical habitat of “Barbus” validus in the Mayi Ndombe River.