Serranochromis swartzi, Stauffer & Bills & Skelton, 2021

Stauffer, Jay R., Bills, Roger & Skelton, Paul H., 2021, Four new species of Serranochromis (Teleostei: Cichlidae) from the Cuanza and Okavango river systems in Angola, including a preliminary key for the genus, Zootaxa 4908 (1), pp. 66-84 : 72-74

Serranochromis swartzi new species

Suggested common name: Red-flanked Largemouth Bream

( Fig. 4 )

Holotype. SAIAB 85174, 135.8 mm SL (male); at bridge between Cimanga and Capunda, Cuanza River, Angola; 10º38’26” S, 17º25’6” E; collected by Ernst Swartz, 23 August 2008.

Paratypes. SAIAB 204368 (13), 106.8–139.5 mm SL; data as for holotype .

Diagnosis. The presence of ocelli throughout the anal fin of breeding males distinguishes S. swartzi from S robustus and S. jallae in which the ocelli in breeding males are restricted to the posterior 4–5 membranes of the anal fin. The exposed teeth of S. swartzi differs from those of S. stappersi and S. altus , which possess small teeth that are buried in the lips. Serranochromis swartzi has an emarginate caudal fin, while S. macrocephalus , S. janus , and S. angusticeps have rounded caudal fins. The shorter jaw of S. swartzi (44.4–52.0 % HL) separates it from S. spei (53.5–57.2 % HL). Serranochromis swartzi has 34–37 lateral-line scales, while S. thumbergi possesses greater than 39 lateral-line scales. The acute angle of the cleft of the mouth (50–60º of horizontal) of S. meridianus delimits it from the 25º angle of S. swartzi . The long dark pectoral fins which reach past the middle of the dorsal fin separates S. longimanus from S. swartzi . The interorbital width (14.3–15.9 % HL) of S. alvum is narrower than that of S. swartzi (17.6–19.8). Serranochromis swartzi has a smaller preorbital depth (16.2–18.9 % HL) and snout length (29.6–31.9 % HL) than Serranochromis cuanza (PD 19.1–22.2, SNL 35.2–39.6 % HL). The greater preorbital depth (19.1–22.2 % HL) of S. swartzi distinguishes it from S. cacuchi , which has a smaller preorbital depth (11.3–15.5 % HL).

Description. Morphometric ratios and meristic data in Table 2. Body shape and pigment patterns in Figure 4 .

Body fusiform and compressed, deepest at origin of dorsal fin. Dorsal-fin origin at vertical through posterior edge of operculum, dorsal fin with XVI-XVII + 12 spines and rays, spines to maximum length over 5–6 spines, dorsal-spine lappets prominent. Soft dorsal deep and pointed behind, not to beyond base of caudal fin. Caudal peduncle long, 16–19% SL, length 1.4–1.6 times depth. Caudal fin broad, relatively short (little more than half the head length), emarginate. Anal fin with III+10 rays, origin closer to caudal-fin base than tip of snout, below vertical through base of penultimate dorsal spine, soft-rayed section with pointed hind edge, not to hind margin of caudal peduncle. Pectoral fin with 13–15 rays, close behind gill slit, ventro-lateral on flanks, base near vertical, pointed, short not beyond pelvic fins. Pelvic fins ventral with strong leading spine 2/3 length of fin, origin narrowly behind vertical through base of pectoral fins, reaching to anus and anterior base of anal fin. Scales small, around 15–18 rows across flanks, dorsal and ventral rows tend to become irregular; 16 rows around the caudal peduncle, 34–37 in lateral line; upper lateral line slightly curved, lower lateral line short but straight; five or six irregular scale rows between anterior dorsal and lateral line, two scale rows between soft dorsal and posterior end of upper lateral line. Chest scales small reduced and irregular.

Head elongate (34.8–38.1 % SL), 2.6–2.8 times in SL, length greater than body depth, acute and pointed with straight predorsal profile extending 35˚ above horizontal. Eyes large (HED 22.3–38.1 % HL; VED 21.1–25.6% HL), dorso-lateral in anterior half of head, entirely above level of the mouth and below the dorsal edge of the operculum. Snout relatively long, greater than orbit diameter, nares in mid-snout before orbits. Lachrymal (preorbit) width equal to orbit diameter. Cheek below and behind orbits deep with 5-6 rows of scales. Post-orbit less than half length of head, interorbit 14.3–15.9 % HL. Mouth terminal, large, protractile; angle of closed jaw of holotype 25˚ below horizontal, posterior premaxilla to below anterior orbit, lips well developed, even along jaws. Teeth caniniform, exposed, narrowly spaced in two to three rows on upper and lower jaws. First branchial arch with 3–4-1-9–12 gill-rakers. Gill opening large, arched from above level of the eye to a vertical below the eye on the ventral side.

Coloration. Preserved specimens brown on flanks, darker on dorsal side, light yellowish brown ventrally. Head with dark interorbital and yellowish gular; broad grey bar on pre-opercle. Single thin lateral band and 8–9 grey vertical bars on body. Dorsal fin with plain brown membranes between anterior seven spines; posterior spinous and rayed membranes with grey blotches. Caudal fin with elongate dark rectangles on membranes and lighter submarginal band. Anal fin with brown membranes and 3–4 irregularly spaced grey blotches. Pelvic and pectoral fins plain brown. Live colours not recorded.

Distribution. Known only from the type locality on the Cuanza River in Angola.

Etymology The specific name swartzi is named after the primary collector Dr. Ernst Swartz - ichthyologist at SAIAB and primary explorer on the Cuanza River programme (2005-2009).

Figures

FIGURE 4. Serranochromis swartzi, SAIAB 85174, 135.8 mm SL; collected from bridge between Cimanga and Capunda, Cuanza River, Angola; 10º38’26” S 17º25’6”E; collected by Ernst Swartz, 23 August 2008.