Synodontis dhonti Boulenger, 1917

Englmaier, Gernot K., Blažek, Radim, Zimmermann, Holger, Bartáková, Veronika, Polačik, Matej, Žák, Jakub, Mulokozi, Deogratias P., Katongo, Cyprian, Büscher, Heinz H., Mabo, Lwabanya, Koblmüller, Stephan, Palandačić, Anja & Reichard, Martin, 2024, Revised taxonomy of Synodontis catfishes (Siluriformes: Mochokidae) from the Lake Tanganyika basin reveals lower species diversity than expected, Zoological Journal of the Linnean Society 202 (3), pp. 1-38 : 13-14

Synodontis dhonti Boulenger, 1917

( Fig. 5 )

Synodontis dhonti Boulenger, 1917: 367 (type locality: Baie de Kilewa , Lake Tanganyika, Democratic Republic of the Congo).

Material examined: Type material: MRAC 14344 , holotype, S. dhonti , 320.4 mm SL, Baie de Kilewa , Lake Tanganyika, Democratic Republic of the Congo, coll. Stappers, 1912 .

Diagnosis: Synodontis dhonti is distinguished from congeners in LT by a unique combination of characters: presence of a large axillary pore; abundant granular papillae on head, body, and fins; 23 mandibular teeth, arranged in six symmetric rows of replacement teeth; 86 primary premaxillary teeth; three secondary branches on inner mandibular barbels; and 43 total vertebrae, with 23 caudal vertebrae.

Description: The general appearance of S. dhonti is shown in Figure 5 ; axial skeleton in Supporting Information, Figure S8A ; and relative measurements, meristic counts, and coded characters are given in Supporting Information, Table S12.

A single specimen, 320.4 mm SL (undetermined sex, MRAC 14344). Body robust, moderately compressed laterally. Dorsal head profile and predorsal back rising straight to dorsal-fin origin at an angle of 20° (against midline of body). Postdorsal profile falling straight to adipose-fin origin and straight to caudal-fin origin. Body depth at anal-fin insertion half of body depth at dorsal-fin origin. Head dorsoventrally compressed; depth at posterior eye margin slightly shorter than maximal cranium width. Snout blunt and half of head length. Mouth subterminal, with abundant papillae on lips; width 72.5% of snout length. Eye diameter less than one-third of snout length.

Dense granular papillae on head, body, and fins. Occipitonuchal shield and humeral process deeply rugose and of granular texture. Humeral process broad and blunt, upper margin almost straight; maximal depth 38.4% of its length. Large, conspicuous axillary pore at anterior ventral margin of humeral process.

Adipose fin well demarcated; basal length 25.0% of SL, extending over 54.2% of distance between dorsal-fin insertion and end of caudal peduncle. Adipose-fin insertion distant to end of caudal peduncle. Dorsal fin with two unbranched and seven branched rays; dorsal spine serrated on lower anterior and upper posterior (17 serrae) edges; length of dorsal spine, excluding upper flexible part, 65.4% of head length. Anal fin with five unbranched and eight branched rays; longest rays reaching beyond level of posterior edge of adipose fin. Pelvic fin with a single unbranched ray and six (seven on the right pelvic fin) branched rays. Pectoral fin with a single unbranched ray and eight branched rays; pectoral spine densely serrated on anterior (31 serrae) and posterior (28 serrae) edges. Pectoral fin shorter than pectoral–pelvic distance, not reaching pelvic-fin origin in folded position. Caudal fin forked with 2 + 15 principal rays; number of upper procurrent rays, 13, less than number of lower procurrent rays, 15.

Mandibular teeth 23, unicuspid, arranged in six rows of replacement teeth. Primary premaxillary teeth 86, arranged in three irregular rows. Secondary and tertiary premaxillary teeth small, arranged in five and one row, respectively.

Maxillary barbels short, reaching beyond pectoral-fin origin but not beyond pectoral-fin insertion. Outer mandibular barbels 31.6% of head length, with five primary branches; secondary branches absent. Inner mandibular barbels with six primary branches and three secondary branches.

Total vertebrae 43, abdominal vertebrae 20, preanal caudal vertebrae three, and postanal caudal vertebrae 20.

Coloration: After long-term preservation in 75% ethanol ( Fig. 5 ), head and body uniformly brown; spots absent. Dorsal and caudal fins dark brown.

Distribution and habitat: Endemic to LT ( Fig. 1 ). Known only from the type locality.

Figures

Figure 1. Map of the Lake Tanganyika basin, including distinct deep-water basins (northern, central, and southern basins) and sampling sites of all examined specimens.Taxonomic diversity of Synodontis species is based on the studies by Poll (1971) and Wright and Page (2006).

Figure 5.General appearance of Synodontis dhonti (MRAC 14344, holotype, 320.4 mm SL, Baie de Kilewa) and shape of humeral process (inset:white outline).

Figure 8. General appearance of Synodontis multipunctatus and shape of humeral process (inset: white outline). A, NMW 100756 (specimen 23-TZ-331), 116.3 mm SL, Cape Kabogo. B, BMNH 1898.9.9.76, holotype, S.multipunctatus, 222.5 mm SL, Sumbu. C, BMNH 1936.6.15.1206-1226, 214.9 mm SL, Kibanga Bay.