Haplochromis glaucus, Vranken & Steenberge & Heylen & Decru & Snoeks, 2022

Vranken, Nathan, Steenberge, Maarten Van, Heylen, Annelies, Decru, Eva & Snoeks, Jos, 2022, From a pair to a dozen: the piscivorous species of Haplochromis (Cichlidae) from the Lake Edward system, European Journal of Taxonomy 815, pp. 1-94 : 34-39

Haplochromis glaucus sp. nov.

urn:lsid:zoobank.org:act:E5948349-E3F9-49A1-81CD-1C7D332E2F00

Figs 1–2 , 17–19 ; Table 1

Differential diagnosis

Species with a piscivorous morphology; snout acute in lateral view; outer oral teeth few and large [UOT 25–47 (median 30)]; males grey with light blue flank and a dusky to black head; female colour pattern similar to males.

Amongst piscivorous species from the Lake Edward system, H. glaucus sp. nov. differs from H. latifrons sp. nov. and H. mentatus by a shorter caudal peduncle [CPL 13.4–16.1 (mean 14.8) vs 15.7–18.0 (16.6– 17.0) % SL]; further from H. latifrons sp. nov. by a longer anal fin base [AFB 17.3–20.3 (18.6) vs 14.7– 17.3 (15.7) % SL] and absence vs presence of a well-defined mid-lateral band; further from H. mentatus by a broader lower pharyngeal bone [LPW 93.3–95.1 vs 83.6–85.7% LPL], a slightly longer pre-pectoral distance [PrP 36.4–39.4 (38.1) vs 33.1–38.2 (36.0) % SL], and dominant males uniformly light blue vs yellow-green with a red anterior part of flank.

It differs from H. rex sp. nov. and H. simba sp. nov. by a broader interorbital area [IOW 50.9–57.1 (53.8) vs 44.9–52.7 (48.1–48.9) % HW]; further from H. rex sp. nov. by a gentler sloping snout (30–40° vs 40–50°), acute vs rounded oral jaws in dorsal view, and dominant males light blue with a blackish operculum and a dusky snout vs cream-coloured with an orange operculum and a light blue snout; further from H. simba sp. nov. by a broader lower pharyngeal bone [LPW 93.3–95.1 vs 83.8–87.9% LPL], absent or weakly developed vs strongly developed mental prominence, and dominant males uniformly light-blue vs yellow with an orange anterior part of flank.

It differs from H. aquila sp. nov. by the combination of a smaller eye [ED 23.2–28.7 (26.8) vs 30.0–31.5 (30.6) % HL], a narrower head [HW 38.9–40.9 (39.7) vs 40.1–43.7 (42.0) % HL], and dominant males light blue with crimson anal and caudal fins vs light grey with bright red anal and caudal fins.

It differs from H. kimondo sp. nov., H. curvidens sp. nov., and H. quasimodo sp. nov. by the combination of a narrower head [HW 38.9–40.9 (39.7) vs 42.0–48.1 (43.4–45.3) % HL], large vs small outer oral teeth, and a smaller number of outer upper jaw teeth [UOT 25–47 (30) vs 43–71 (49–58)]; further from H. kimondo sp. nov. and H. quasimodo sp. nov. by dominant males light blue vs grey dorsally and yellow or blue-black ventrally.

It differs from H. falcatus sp. nov. by the combination of a shorter pre-dorsal distance [PrD 35.4–37.0 (36.1) vs 36.9–41.1 (39.5) % SL], a steeper lower jaw side (35–45° vs 15–25°), weakly recurved vs strongly recurved outer oral teeth, and dominant males uniformly light blue vs olive-green with an orange-red anterior part of flank.

It differs from H. pardus sp. nov. by the combination of deeper lacrimal [LaD 18.0–22.7 (19.8) vs 16.0–18.3 (17.3) % HL], a broader interorbital area [IOW 50.9–57.1 (53.8) vs 39.3–48.4 (44.6) % HW], and dominant males light blue vs speckled to uniformly black.

It further differs from H. squamipinnis by the combination of a gentler gape inclination (20–30° vs 30–45°), absence vs presence of minute scales on proximal parts of dorsal and anal fins, and dominant males light blue vs slate blue.

Etymology

Specific name from the Latin ‘ glaucus ’ for ‘greyish blue’; referring to grey and light-blue colour pattern of all adult specimens.

Material examined

Holotype UGANDA • ♂, 106.2 mm SL; Lake Edward, Kayanja offshore; 0°05′34.8″ S, 29°45′28.8″ E; 21 Mar. 2019; HIPE4 exped. leg.; RMCA 2019.002.P.0016 .

Paratypes DEMOCRATIC REPUBLIC OF THE CONGO • 1 ♂, 158.3 mm SL; “Lac Edouard: au large de la riv. Kigera” [Lake Edward: offshore Kigera river ]; 0°29′42″ S, 29°38′14″ E (inferred); 25 May 1953; KEA exped. leg.; IRSNB 13477 • 1 ♂, 150.9 mm SL; “Lac Edouard: 2–3 km ± 500 m au large à l’Ouest de Kiavinionge” [Lake Edward: 2–3 km ± 500 m offshore west of Kiavinionge ]; 0°11′39″ S, 29°32′31″ E (inferred); 1 Jun. 1953; KEA exped. leg.; IRSNB 13480 .

UGANDA – Lake Edward • 1 ♀, 1 ♂, 90.7–93.6 mm SL; Kagoro fishing ground; 0°12′50.1″ S, 29°49′19.7″E; 4 Feb. 2018; HIPE3 exped. leg.; open water; RMCA 2018.008.P.0365 to 0366 • 1 ♀, 92.6 mm SL; same collection data as for preceding; RMCA 2018.008.P.0367 • 1 ♀, 1 ♂, 102.1– 104.7 mm SL; Kayanja offshore; 0°05′34.8″ S, 29°45′28.8″ E; 21 Mar. 2019; HIPE4 exped. leg.; RMCA 2019.002.P.0017 to 0018 • 1 ♂, 2 ♀♀, 107.7–122.3 mm SL; same collection data as for preceding; RMCA 2019.002.P.0019 to 0021 .

Description

Based on 11 specimens (90.7–158.3 mm SL); body shallow ( Table 1 ) and oval ( Fig. 17 ). Head long, very narrow, and with a straight dorsal outline; eye small; interorbital area narrow; lacrimal and cheek deep. Snout long, rounded in dorsal view, very narrow, acute, and slopes gently at 30–40°; premaxillary pedicel long and weakly prominent. Jaws long, relatively stout, narrow, isognathous, and acute in dorsal view; gape large and slopes gently at 20–30°; maxilla extends (almost) to vertical through anterior margin of orbit. Lower jaw relatively stout and with a straight to slightly convex ventral outline in lateral view, mental prominence absent or weakly developed, and lower jaw side steep with an inclination of 35–45° to horizontal in anterior view. Upper jaw expanded anteriorly and weakly ventrally. Lips and oral mucosa large. Neurocranium shallow, ethmo-vomerine block decurved, preorbital region shallow (20–23% NL), orbital region shallow (28–31% NL), and supraoccipital crest shallow and wedge-shaped ( Fig. 18b ).

Outer oral teeth few, unicuspid, and very large. Necks conical, stout, and straight; crowns recurved and acutely pointed. Dental arcades rounded. Outer teeth widely and irregularly set with neck-distances of 1–4 neck-widths. In upper jaw, 1–3 posteriormost teeth slightly enlarged. Inner teeth small, strongly recurved, unicuspid, and acutely pointed. Tooth bands very slender crescent-shaped with 1–3 rows of inner teeth, and narrow posteriorly until only outer row remains past ¾ length of tooth band. Inner teeth closely and regularly set on 1–2 outer neck-widths from outer row; implantation recumbent; size decreases slightly buccally and posteriorly.

Lower pharyngeal bone average in length, triangular, slim, and shallow over whole length ( Fig. 19 ). Pharyngeal teeth relatively large and slender; major cusps acutely pointed; cusp gaps straight; minor cusps and cusp protuberances mostly absent. Teeth in two median longitudinal rows equal in size and form to lateral teeth, 10–12 in each row. Posterior transverse row with 15–16 teeth, implanted recumbently with a lateral inclination; major cusps recurved, bluntly pointed, and laterally compressed; minor cusps small.

Chest scales small; transition to larger flank scales gradual. Minute scales on proximal half of caudal fin.

Caudal fin emarginate; dorsal and anal fins reach to between verticals through one scale anterior to and two scales posterior to caudal-fin base. Pectoral and pelvic fins reach to between anal opening and first anal-fin spine; first branched pelvic-fin ray not elongated.

Ceratobranchial gill rakers in outer row of first gill arch short, stout, and simple; posteriormost rakers anvil-shaped to rarely weakly trifid. Epibranchial gill rakers slender and simple.

Colouration in life

Dominant males: flank and caudal peduncle light-blue; dorsum grey with a yellow sheen; belly, chest, and operculum blackish with a yellow sheen; flank with 5–7 faint vertical stripes ( Fig. 18c ). Preoperculum black; cheek black with blue sheen; lacrimal and snout dusky; lower jaw blackish; branchiostegal membrane black; eye with dark grey outer ring and silver inner ring. Nostril, interorbital, supraorbital, and lacrimal stripes well-defined; nape band, vertical preopercular stripe, and mental blotch present; operculum with black posterior border. Pectoral and dorsal fins hyaline; dorsal fin with black lappets, dusky base, and dusky and maculated crimson posterior part. Anal and caudal fins crimson; anal fin with dusky posterior part and 1–2 large orange egg-spots with dusky rings; caudal fin with dusky base, hyaline posterior part, and crimson maculae.

Females: strikingly similar to dominant males. Body, dorsum, and caudal peduncle grey with a yellow sheen; flanks light blue and with 5–7 faint vertical stripes; belly and chest blackish with a yellow sheen ( Fig. 18d ). Operculum, preoperculum, cheek, lacrimal, and snout grey; operculum with blue sheen; cheek with black sheen; lower jaw blackish; branchiostegal membrane black; eye with dark grey outer ring and silver inner ring. Nostril, interorbital, supraorbital, and lacrimal stripes well-defined; nape band, vertical preopercular stripe, and mental blotch faint; operculum with faint black posterior border. Pectoral and dorsal fins hyaline; dorsal fin with black lappets, dusky base, and dusky posterior part. Anal and caudal fins yellow with a red sheen; anal fin with hyaline posterior part and 1–2 spots resembling egg-spots; caudal fin with dusky base, hyaline posterior part, and dusky maculae. Juveniles: dorsum greyish, belly, chest, operculum, and cheek white; transition gradual. Nostril, interorbital, supraorbital, and lacrimal stripes, nape band, and mental blotch faint. Pectoral, pelvic, dorsal, and anal fins hyaline; dorsal fin with black lappets and dusky base and posterior part; anal fin with a yellow sheen and 1–2 spots resembling egg-spots. Caudal fin dusky and with black maculae and a yellow ventral part.

Preserved colouration

Dorsum brown; belly and chest speckled black; flank dark yellowish and with 6–8 faint vertical stripes. Cheek yellow and speckled black; snout dusky; lower jaw and pre- and subopercula black ( Fig. 18a ). Nostril, interorbital, and vertical preopercular stripes well-defined; lacrimal stripe broad and welldefined; supraorbital stripe and nape band faint. Pectoral and anal fins hyaline; anal fin with black lappets, a dusky posterior margin, and 1–2 large egg-spots; pelvic fin black; dorsal fin dusky and with black lappets and a maculated posterior part; caudal fin dorsally dusky, ventrally hyaline, and with a dusky base.

Distribution and ecology

Only known from Lake Edward, found over sandy substrates. Based on its morphology, most probably a piscivorous species.

Figures

Fig. 1. The Lake Edward system, consisting of Lakes Edward and George that are connected through the Kazinga Channel. The catch localities of all examined specimens are indicated: Haplochromis sp. ‘latifrons’ (), H. mentatus Regan, 1925 (), H. sp. ‘rex’ (), H. sp. ‘simba’ (▼), H. sp. ‘glaucus’ (), H. sp. ‘aquila’ (), H. sp. ‘kimondo’ (●), H. sp. ‘falcatus’ (), H. sp. ‘curvidens’ (), H. sp. ‘pardus’ (), H. sp. ‘quasimodo’ (▲), and H. squamipinnis Regan, 1921 (█). The type localities of H. mentatus and H. squamipinnis are not shown as the exact locations are unknown.

Fig. 2. a. Differences in total number of outer teeth and premaxillary dentition between the macro- and microdontic groups of piscivores from the Lake Edward system.b. Schematic presentation of the dominant male colour patterns in life, in the various groups studied. For H. sp. ‘latifrons’ the female and for H. sp. ‘curvidens’ the non-dominant colour patterns are shown, as those of dominant males are unknown.

Fig. 17. Haplochromis glaucus sp. nov., holotype, ♂, 106.2 mm SL (RMCA 2019.002.P.0016). Drawn by N. Vranken.

Fig. 18. Haplochromis glaucus sp. nov. a. Photograph of preserved holotype (RMCA 2019.002.P.0016; 106.2 mm SL). b. X-ray image of holotype c–d. Photographs of freshly caught specimens. c. Dominant male, the holotype. d. Female (RMCA 2019.002.P.0017; 102.1 mm SL) to illustrate the live colour patterns. The contrast was slightly enhanced.

Fig. 19. Haplochromis glaucus sp. nov. (RMCA 2019.002.P.0020; 110.9 mm SL). a. Dorsal view of the lower pharyngeal jaw. b. Lateral view of the lower pharyngeal jaw.