Serranochromis cuanza, 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 : 74-77

Serranochromis cuanza new species

Suggested common name: Black-finned Largemouth Bream

( Fig. 5 )

Holotype. SAIAB 84888 , 181.0 mm SL (male); collected from Posto 5 on the Cuanza River, Angola, 09º48’23” S, 15º24’30” E collected by Ernst Swartz, 31 October 2007.

Paratypes. SAIAB 84791 , 7 , 49.6–123.4 mm SL; data as for holotype .

Diagnosis. The presence of ocelli throughout the anal fin of breeding males distinguishes S. cuanza 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. cuanza differs from those of S. stappersi and S. altus , which possess small teeth that are buried in the lips. Serranochromis cuanza has an emarginate caudal fin, while S. macrocephalus , S. janus , and S. angusticeps have rounded caudal fins. The shorter jaw of S. cuanza (44.3–52.8 % HL) separates it from S. spei (53.5–57.2 % HL). Serranochromis cuanza has 36–37 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. cuanza . The long dark pectoral fins which reach past the middle of the dorsal fin separates S. longimanus from S. cuanza . The interorbital width of S. cuanza (16.3–18.0% HL) is narrower than that of S. cacuchi (20–21.7 % HL). Serranochromis cuanza has a greater preorbital depth (19.1–22.2% HL) and snout length (SNL 35.2–39.6% HL) than S. swartzi (PD 16.2.1–18.9, SNL 29.6–31.9% HL). The interorbital width of S. cuanza (16.3–18.0) is wider than that of S. alvum (14.3–15.9 % HL).

Description. Description. Morphometric ratios and meristic data in Table 3. Body shape and pigmentation patterns in Fig 5 .

Body fusiform and compressed, deepest at origin of dorsal fin. Dorsal-fin origin at vertical through posterior edge of operculum; dorsal fin with XV + 12–14 spines and rays; dorsal spines increase to maximum length over 5–6 spines, lappets prominent. Soft dorsal deep and obtusely pointed behind, extending to base of caudal fin. Caudal peduncle long, 5.3–6.3 times in SL (16–19% SL), length 1.3–1.5 times depth. Caudal fin broad, relatively short rectangular (little more than half the head length), emarginate. Anal fin with III+10 rays, origin behind mid body, closer to caudal-fin base than tip of snout, below vertical through base of ultimate dorsal spine, soft-rayed section with pointed hind edge, extending to base of caudal fin. Pectoral fin with 12–14 soft rays, close behind gill slit, ventro-lateral on flanks, base near vertical, pointed paddle-shaped, 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, with 18–20 regular rows across flanks from dorsal-fin origin to anal-fin origin; 16 scale rows around the caudal peduncle, 36–37 in lateral line, pores complete; upper lateral line nearly straight, slightly curved, lower lateral line straight through mid-caudal peduncle; five or six 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 triangulate, length slighter greater than body depth, 2.5–2.7 times in SL (36.4–39.5% SL); predorsal profile straight, angle 30˚. Eyes large (HED 21.3–30.9 % HL; VED 20.1–30.4 % 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 subequal to orbit diameter, 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. 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, curved from above level of eye to mid-ventrally through a vertical below eye.

Coloration. Head and body brown in preserved specimens. Laterally with single thin mid-lateral band and 8–9 regular bars from dorsum to lower flank. Dorsal fin with greyish brown membranes, rayed membranes with proximal dark spots and distal streaks. Caudal fin brown. Anal fin brown with light indications of egg spots. Pectoral and pelvic fins plain light brown. In life, metallic silvery on sides from head to caudal peduncle, dorsum mixed copperyolive, white ventral surface; iris a deep purple-charcoal to reddish around the black pupil; upper operculum with metallic golden tinge; opercular spot grey, metallic light blue over exposed maxilla; inter-spinous membranes of dorsal fin light grey with darker grey posterior edges, lappets tinged with red, soft rayed membranes with light and dark blocks proximally, plain greyish distally; caudal fin with light rays and pale grey membranes forming blocks proximally; anal fin an overall yellow cast with greyish infusion, 4–5 scattered greyish egg spots with lighter margins on medial and posterior membranes; pectoral-fins colourless off-white; pelvic-fins yellow infused with grey, spines dusted sooty grey.

Distribution. Known only from the collection locality Posto 5 on the Cuanza River, below Capanda Dam, Angola.

Etymology. The specific name cuanza , a noun in apposition, refers to the Cuanza River, spelt as generally done in Angola. The species is most likely endemic to the Cuanza River system.

Figures

FIGURE 5. Serranochromis cuanza, SAIAB 84888, 181.0 mm SL; collected from Posto 5 09º48’23”S 15º24’30”E collected by Ernst Swartz, 31 October 2007.