Clarias monsembulai, Bernt & Stiassny, 2022

Bernt, Maxwell J. & Stiassny, Melanie L. J., 2022, A New Species of Air-breathing Catfish (Clariidae: Clarias) from Salonga National Park, Democratic Republic of the Congo, American Museum Novitates 2022 (3990), pp. 1-20 : 4-9

Clarias monsembulai , new species

Figures 2–5 , table 1

Clarias buthupogon (in part): Monsembula Iyaba and Stiassny (2013).

HOLOTYPE: AMNH 244176 , 1, 226 mm SL, Democratic Republic of the Congo, Equateur, Salonga National Park , Luilaka River at Ilenge, 2°35′ 47″S, 21°34′ 36″E. R. J.C. Monsembula Iyaba, 11 November 2007.

PARATYPES: AMNH 244163 , 1, 244 mm SL; Yenge River ca. Boyenga, 1°03′50″S, 20°44′44″E ; AMNH 252236 , 3 , 164–193 mm SL; small stream at Katanyongo , near Salonga National Park, 2°08′10.7″S, 21°07′9.5″E ; AMNH 244162 , 1, 183 mm SL; Salonga River at Watsikengo ; AMNH 252219 , 2 , 187–231 mm SL; Salonga National Park at Bekongo, 1°54′42.74″S, 20°51′11.35″E ; AMNH 244164 , 1, 127 mm SL, Luilaka River , beach at Monkoto ; AMNH 252267 , 1, 179 mm SL, Mpongo , large stream ca. 2 kilometers from Luilaka River, near Salonga National Park, 1°55′19.9″ S, 20°51′49.8″E ; AMNH 252222 , 1, 167 mm SL; Luilaka River at Lokaka in Salonga National Park, 2°0′24.9″S, 20°58′6.2″E ; RMCA 2022-019 -P-0001-0002, 2, 143–172 mm SL, Salonga River at Watsikengo .

NONTYPE SPECIMENS: AMNH 242721 , 14 , 54–81 mm SL, small tributary of Luilaka River near Monkoto in Salonga National Park, 1°45′0″S, 20°40′49.9″E .

DIAGNOSIS: Clarias monsembulai can be distinguished from all congeners, with the exception of C. buthupogon , by its exceptionally long maxillary barbels (60% of standard length or greater) vs. maxillary barbels less than 60% SL (usually considerably less). It differs from C. buthupogon in the absence of fine, pale spots over the surface of the body and by an exposed bony surface of the cleithrum reaching 14%–20% of head length (vs. cleithrum deeply imbedded in soft tissue with only a narrow bony ridge visible externally). Clarias monsembulai can be further differentiated from C. angolensis , the species with which it shares closest phenotypic similarity, by longer nasal barbels (37%–51% SL vs. 22%–34% SL), longer internal mandibular barbels (29–37% SL vs. 16–27% SL), longer external mandibular barbels (45%–57% SL vs. 24%–40% SL); and by the coloration of maxillary barbels which are white or cream-colored distally over more than half of their length (vs. brown or gray over more than half their length).

DESCRIPTION: Morphometrics summarized in table 1. Maximum observed total length 270 mm (standard length 244 mm). Head broad, depressed with slightly convex dorsal profile, snout rounded. Anterior nares tubular, medial to posterior nares and nasal barbels. Mouth subterminal, lips and bases of barbels papillose. Four pairs of barbels, all extending beyond dorsal fin origin. Barbels rounded at base, becoming flat, ellipsoid in cross section. Body cylindrical between head and anal fin origin, becoming laterally compressed posteriorly.

Dorsal fin with 80–86 rays, originating a short distance (less than 10% SL) behind supraoccipital process. Anal fin with 57–61 rays, origin nearly equidistant from snout tip and caudal fin base. Dorsal and anal fins not confluent with caudal fin. Pectoral fin with robust spine and 10–12 rays. Spine sharply pointed with slight posterior curve. Strong serration present on both anterior and posterior margins. Serrae angled proximally, larger on posterior margin, increasing in number with body size. Pelvic fins present on all specimens examined, with six rays. Caudal fin rounded, with 18–22 rays.

Elements of skull and pectoral girdle shown in figure 3. Neurocranium robustly ossified. Fourth infraorbital contacting suprapreopercle in all specimens examined (80–244 mm SL). Frontal fontanel long and narrow (knife shaped). Supraoccipital fontanel narrowly oblong, supraoccipital process sharply pointed in both juveniles and adults.

Premaxillary and vomerine tooth plates similar in width, about 30% of head length. Premaxillary teeth villiform. Vomerine toothplate with short posterior median process, teeth subgranular. Dentary teeth villiform, extending over half of dorsal surface, nearly reaching coronoid process. First branchial arch with 16–18 slender gill rakers. Second and fourth arches diverticulate, forming arborescent suprabranchial organ (fig. 4). Rosette on second arch with few branches, not overlapping larger, more extensively, branched rosette on fourth arch. Respiratory organ occupies approximately one fourth of suprabranchial chamber volume. Seven or eight branchiostegal rays. Urohyal trifurcate, lateral processes longer than posteromedial process. Cleithrum superficial, visible externally as striated bony band at isthmus (fig. 5). Coracoid with single circular foramen at margin with cleithrum near articulation with pectoral spine.

Parapophyses of fourth and fifth vertebrae expanded, forming hourglass-shaped Weberian apparatus encapsulating bilobed gas bladder. Posterolateral processes of os suspensorium forming ventral floor of Weberian capsule. Fifty-eight to 61 (mode = 60) vertebrae posterior to first four vertebrae comprising Weberian apparatus. Two free neural spines between skull and first dorsal-fin pterygiophore. First rib articulated with seventh vertebra, 12 ribs present. No fusion of caudal fin hypurals.

COLORATION: Preserved specimens are dark brown dorsally, fading to light brown, gray, or cream colored ventrally. Some lighter colored specimens exhibit a faint mottling of irregular dark brown markings over a slightly lighter background. Fins uniformly dark brown. Barbels brown at base, becoming creamy white over most of their length. Underside of head pale, but with band of dark pigment above fleshy furrow between mandibular barbels and isthmus. Lateral line visible as a series of small regularly spaced white pores extending from the base of the head to the base of the caudal peduncle. Pores of the secondary canals of the lateral line system form a regular pattern over the flanks, but these pores are not readily visible against the darkly pigmented skin.

DISTRIBUTION: The species is currently known only from the Momboyo, Luilaka, Salonga, and Yenge river systems within the Cuvette Centrale of the middle Congo River Basin (fig. 6). However additional collecting throughout the region will likely extend this range (E. Decru, personal commun.).

ETYMOLOGY: Named in honor of Raoul Monsembula Iyaba (professor of biology, University of Kinshasa) for collecting the type series of this species, and in recognition of his substantial contributions to central African ichthyology .

Figures

FIGURE 2. Lateral view of Clarias monsembulai new species, holotype AMNH 244176, 226 mm SL. Luilaka River at Ilenge, Salonga National Park. Scale bar = 1 cm.

FIGURE 3. Computed tomography scan reconstruction of the skull and pectoral girdle of Clarias monsembulai (at left and above), AMNH 252267, 179 mm SL in A, dorsal; B, ventral; and C, lateral views. Abbreviations: ang, anguloarticular; apal, autopalatine; br, branchiostegal rays; ch-a, anterior ceratohyal; ch-p, posterior ceratohyal; cl, cleithrum; cor, coracoid; den, dentary; fr, frontal; hhv, ventral hypohyal; hm, hyomandibula; io-ii, infraorbital ii; io-iii, infraorbital iii; io-iv, infraorbital iv; iop, interopercle; lac, lacrimal; leth, lateral ethmoid; meth, mesethmoid; mx, maxilla; na, nasal; ns, neural spines; op, opercle; o-susp, os suspensorium; pmx, premaxilla; pop, preopercle; pp-v4, parapophysis of 4th vertebra; pp-v5, parapophysis of 5th vertebra; ps, pectoral spine; pt, pterotic; pt-scl, posttemporo-supracleithrum; q, quadrate; rad, radials; soc, supraoccipital; sph, sphenotic; spop, suprapreopercle; trsc, transcapular process; uh, urohyal; vo, vomer. Scale bars = 1 cm.

FIGURE 4. Suprabranchial organ of Clarias monsembulai, AMNH 244162, 165 mm SL (suprapreopercle removed). Scale bar = 1 cm.

FIGURE 5. Exposed cleithrum (demarcated by dashed line) of A, Clarias buthupogon, AMNH 227571, 162 mm SL and B, Clarias monsembulai, AMNH 244162, 183 mm SL. Scale bar = 1 cm.