Synodontis tanganyicae Borodin, 1936

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) : -

Synodontis tanganyicae Borodin, 1936

( Fig. 12)

Synodontis tanganyicae Borodin, 1936: 9 (type locality: Kasanga , Lake Tanganyika, Tanzania).

Synodontis lacustricolus Poll, 1953: 157 (type locality: Au large de Karema, Lake Tanganyika , Tanzania).

Material examined: Type material: MCZ 32538 , lectotype, S. tanganyicae , 321.0 mm SL, Kasanga , Lake Tanganyika, Tanzania, coll. Loveridge , 1930 (photographs and radiographs examined). MCZ 147517 , paralectotype, S. tanganyicae , 403.6 mm SL, Kasanga , Lake Tanganyika, Tanzania, coll. Loveridge , 1930 (photographs examined). ISRNB 197 , holotype, S. lacustricolus , 493.0 mm SL, Au large de Karema, Tanganyika Territory, Lake Tanganyika, Tanzania, coll. Explo. Hydrobiol. L. Tanganyika , 1946–1947. ISRNB 198 , paratype, S. lacustricolus , 352.0 mm SL, Baie de Tembwe , dist. Tanganika, Congo Belge, Lake Tanganyika, Democratic Republic of the Congo, coll. Explo. Hydrobiol. L. Tanganyika , 1946–1947. ISRNB 199 , paratype, S. lacustricolus , 344.5 mm SL, Baie de M’Vua , dist. Tanganika, Congo Belge, Lake Tanganyika, Democratic Republic of the Congo, coll. Explo. Hydrobiol. L. Tanganyika , 1946–1947. BMNH 1955.12 .20.1851, paratype, S. lacustricolus , only head, Malagarasi , Lake Tanganyika, Tanzania, coll. Explo. Hydrobiol. L. Tanganyika , 1946–1947. BMNH 1955.12 .20.1849, paratype, S. lacustricolus , 315.0 mm SL, Opposite Kala , Lake Tanganyika, Tanzania, coll. Explo. Hydrobiol. L. Tanganyika , 1946–1947. BMNH 1955.12 .20.1850, paratype, S. lacustricolus , 291.0 mm SL, Tembwe Bay , Lake Tanganyika, Democratic Republic of the Congo, coll. Explo. Hydrobiol. L. Tanganyika , 1946–1947. MRAC 90290 , paratype, S. lacustricolus , 363.2 mm SL, Baie de Karago , stat. 309, Lake Tanganyika, Tanzania, coll. Poll , 1947. MRAC 90288 , paratype, S. lacustricolus , 416.6 mm SL, Baie de Tembwe , stat 118, Lake Tanganyika, Democratic Republic of the Congo, coll. Poll , 1947. MRAC 90289 , paratype, S. lacustricolus , 486.2 mm SL, Baie d’Edith , stat. 121, Lake Tanganyika, Democratic Republic of the Congo, coll. Poll , 1947.

Non-type material: BMNH 1936.6.15.1203–1205, three, 328.0– 423.0 mm SL, Lake Tanganyika, coll. Christy. MRAC 130720, one, 254.6 mm SL, Ile de Mboko, North Lake Tanganika, Democratic Republic of the Congo, coll. Marlier, 1957. MRAC 1996.083.P.0003-0004, two, 238.9–262.9 mm SL, Nkamba Bay, in front of Kasaba Bay Lodge, Sumbu National Park, Lake Tanganyika, Zambia, coll. De Vos, 1995.

Diagnosis: Synodontis tanganyicae 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; 38–50 (median 46) mandibular teeth, commonly arranged in eight symmetric rows of replacement teeth; 105–226 (median 162) primary premaxillary teeth; 4–8 (median 6) secondary branches on inner mandibular barbels; and 40–41 (median 41) total vertebrae, with 22–24 (median 23) caudal vertebrae.

Description: The general appearance of S. tanganyicae is shown in Figure 12; axial skeletons in Supporting Information, Figure S8K, L; and relative measurements, meristic counts, and coded characters are given in Supporting Information, Table S12.

Longest examined specimen 493.0 mm SL (male, ISRNB 197, holotype, S. lacustricolus ). Body robust. Dorsal head profile and predorsal back rising straight to dorsal-fin origin at an angle of 22° (against midline of body), slightly concave at occiput. Postdorsal profile falling straight to adipose-fin origin and straight to caudal-fin origin. Body depth at anal-fin insertion greater than half of body depth at dorsal-fin origin. Head dorsoventrally compressed; depth at posterior eye margin usually smaller than maximal cranium width. Snout blunt and slightly longer than half of head length. Mouth subterminal, with abundant papillae on lips; width 69.9%–100.2% of snout length. Eye diameter less than one-third of snout length.

Dense, granular papillae on head, body, and partly on fins. Occipitonuchal shield and humeral process deeply rugose and of granular texture. Humeral process deep and pointed; maximal depth 40.1%–46.8% (N = 5) of its length. Large, conspicuous, axillary pore at anterior ventral margin of humeral process.

Adipose fin well demarcated; basal length 21.9%–26.0% SL, extending over 49.2%–64.8% 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 rays and commonly seven branched rays; dorsal spine densely serrated on lower anterior edge, poorly marked serrations on upper anterior edge, posterior edge with 10–16 serrae; length of dorsal spine, excluding upper flexible part, 49.5%–69.6% of head length, and shorter than length of pectoral spine (excluding upper flexible part). Anal fin with five unbranched rays and commonly eight branched rays; anal-fin rays reaching beyond level of posterior edge of adipose fin. Pelvic fin with a single unbranched ray and six branched rays. Pectoral fin with a single unbranched ray and nine branched rays; pectoral spine serrated on anterior (20–40 serrae) and posterior (21–29 serrae) edges; length not reaching beyond pelvic-fin origin in folded position. Caudal fin forked with 2 + 15 principal rays; number of upper procurrent rays (13–17, median 15, N = 8) less than number of lower procurrent rays (14–19, median 17, N = 16).

Mandibular teeth 38–50 (median 46, N = 17) (lectotype of S. tanganyicae 43, holotype of S. lacustricolus 45), unicuspid, arranged in eight or 10 symmetric rows of replacement teeth. Primary premaxillary teeth 105–226 (median 162, N = 17) (lectotype of S. tanganyicae 121, holotype of S. lacustricolus 221), arranged in 5–8, commonly 6, irregular rows.

Maxillary barbels long, commonly reaching beyond pectoral-fin insertion (only in 1 of 17 specimens shorter). Outer mandibular barbels 37.4%–56.0% of head length, with 5–8 (median 7, N = 16) primary branches; secondary branches observed in only two specimens. Inner mandibular barbels with 7–13 (median 9, N = 16) primary branches and 4–8 (median 6, N = 17) secondary branches.

Total vertebrae 40–41 (median 41, N = 10), (lectotype of S. tanganyicae 41), abdominal vertebrae 17–19 (median 18), preanal caudal vertebrae 3–4 (median 4), and postanal caudal vertebrae 18–20 (median 19).

Coloration: After long-term preservation in 75% ethanol ( Fig. 12C), head and body uniform brown; fins usually darker. Some specimens with abundant, small, dark brown spots on head, body, and fins.

Distribution and habitat: Endemic to LT ( Fig. 1). According to Poll (1953), a widely distributed species over rocky and muddy substrates at depths of 20– 60 m. Occurring as deep as 130 m ( Coulter 1991). Last recorded in 1995 ( De Vos and Thys van den Audenaerde 1998).

The (primarily) riverine species of Synodontis in the Lake Tanganyika basin