Serranochromis cacuchi, 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 : 77-79

Serranochromis cacuchi new species

Suggested common name: Cacuchi Largemouth Bream

Fig. 6 .

Holotype. SAIAB 186684 , 181.9 (male) mm SL; collected from the Cacuchi River , approximately 15 km south west of Chitembo Village at the bridge on the main road north from Menongue , tributary of Cuchi, Cubango (Okavango) River system, Angola; 13º35’39.6” S, 16º52’49.8” E. Collected by R. Bills, P. H. Skelton, F. de Almeida, 11 May 2012.

Paratypes. SAIAB 186674 , (4) 132.7–191.5 mm; data as for holotype

Diagnosis. The presence of ocelli throughout the anal fin of breeding males distinguishes S. cacuchi from 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. cacuchi differs from those of S. stappersi and S. altus , which possess small teeth that are buried in the lips. Serranochromis cacuchi has an emarginate caudal fin, while S. macrocephalus , S. janus , and S. angusticeps have rounded caudal fins. The shorter jaw of S. cacuchi (47.8–52.3 % HL) separates it from S. spei (53.5–57.2 % HL). Serranochromis cacuchi has 32–33 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. cacuchi . The long dark pectoral fins which reach past the middle of the dorsal fin separates S. longimanus from S. cacuchi . The interorbital width (20.0–21.7 % HL) delimits S. cacuchi from S. alvum (14.3–15.9 % HL).The snout length of S. cacuchi (35.2–39.6 % HL) is longer than that of S. alvum (30.3–34.9 % HL) and S. cuanza (26.9–34.7 % HL). The larger preorbital depth of S. cacuchi (19.1–22.2 % HL) distinguishes it from S. swartzi (16.2–18.9 % HL).

Description. Morphometric ratios and meristic data in Table 4. Body shape and pigment patterns in Fig 6 .

Body slender, fusiform, and compressed, deepest at origin of dorsal fin. Predorsal profile straight at 30˚ to horizontal, with shallow kink at interorbit and gentle curve towards dorsal fin. Dorsal-fin origin at vertical through posterior edge of operculum, dorsal fin with XIV-XV + 12–13 spines and rays, spines increase to maximum length over 5–6 spines, spine lappets prominent. Soft dorsal pointed behind, not beyond base of caudal fin. Caudal peduncle moderately long, 16–20 % SL, length 1.4–1.8 times depth. Caudal fin broad, relatively short (around half the head length), emarginate. Anal fin with III+9 spines and rays, origin well behind midline and closer to caudal-fin base than tip of snout, below vertical through base of ultimate dorsal spine, soft-rayed section with pointed hind edge, not extending to below base of caudal fin. Pectoral fin close behind gill slit, base inclined ventro-lateral on flanks, obtusely pointed, to pelvic extremity. Pelvic fins ventral, with strong spine half a length of fin, origin narrowly behind base of pectoral fins, not reaching to anus and anterior base of anal fin. Scales small, with around 14 regular rows across flanks; 16 rows around the caudal peduncle, 32–33 in lateral line; upper lateral line gently curved, lower lateral line short but straight; three 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 2.7 times in SL (36.6–37.5 % SL), length greater than body depth, acute and pointed with marginally kinked predorsal profile, extending 30–35˚ above horizontal. Eyes large (HED 18.5–24.5 % HL; VED 17.7–22.3 % HL), dorso-lateral in anterior half of head, entirely above level of the mouth and at level of dorsal edge of the operculum. Snout relatively long, 2–3 times orbit diameter (35.2–39.6 % HL), nares in mid-snout before orbits. Preorbital depth (lachrymal) 1.5 times orbit diameter. Cheek below and behind orbits deep with 4–5 rows of scales. Post-orbit less than half length of head, interorbit sub-equal to orbit diameter (20.0–21.7 % HL). Mouth terminal, large (lower jaw 47.8–52.3 % HL), protractile, angle of closed jaw of holotype 25˚ below horizontal, posterior pre-maxilla to below anterior orbit, lips well developed, even along jaws. Teeth caniniform, exposed, narrowly spaced in two rows on upper and 2–3 rows on lower jaws. First branchial arch with 3–4-1-10–11 gill-rakers. Gill opening large, curved from level of eye to midventral below vertical through eye.

Coloration. Preserved holotype shades of brown and grey as in Fig 6 . In life, head with dark interorbital, dark bar from orbit to posterior maxilla and white gular; green-blue highlights and small orange-red spots on cheek, opercle and preopercle; dark opercular spot. Ventral head, throat to base of pectorals and belly white. Laterally dark grey patch above pectoral base, lower flanks yellow to light green, whitish ventrally, dark olive-grey across dorsum, with single thin lateral band and 8–9 short bars; dark orange-red spots in centre of each scale forming 8–10 rows, green-blue highlights between spots. Dorsal fin with membranes between anterior 7–9 spines olive proximally to grey distally; posterior spinous and rayed membranes light olive yellow with rows of dark grey spots, lappets and dorsal edge to tip of soft-rayed bright red with narrow pale blue submarginal band. Caudal fin light olive-yellow with dark spots scattered throughout membranes and forming bars, broad light grey margin. Anal fin with yellow cast and rows of 2–5 red egg spots along membranes including distal single egg spots over spines, thin charcoal dusted margin along ventral edge. Pelvic and pectoral fins clear with feint yellow cast.

Habitat. The Cacuchi River at the collection site is a fast-flowing rocky substrate river ( Fig. 7 ). There were several channels with only one flowing at the time of sampling. Specimens were caught in the margins of the main rocky channel with electric fishing and large hand D-nets. They came from deep rock boulder crevices. Water depths were between 0.5–1.0m.

Distribution. Currently known only from the type locality on the Cacuchi River, tributary of the Cuchi-Cubango River in Angola, approximately 15 km south west of Chitembo Village at the bridge on the main road north from Menongue.

Etymology. The specific name cacuchi a noun in apposition refers to the Cacuchi River where this species was collected and is most likely narrowly endemic.

Figures

FIGURE 6. Serranochromis cacuchi, SAIAB 186684, 181.9 mm SL; collected from Bridge of 1000 mines north of Mambue 13º35’39.6”S 16º52’49.8”E. Collected by R. Bills, P. Skelton, F. de Almeida, 11 May 2012.

FIGURE 7. The Cacuchi River at the collection site of Serranochromis cacuchi.