Haplochromis aquila, 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 : 39-43

Haplochromis aquila sp. nov.

urn:lsid:zoobank.org:act:18BC8C85-5A02-48F0-8D90-7B069122A09D

Figs 1–2 , 20–22 ; Table 1

Differential diagnosis

Species with a piscivorous morphology; eye large [ED 30.0–31.5 (mean 30.6) % HL]; outer oral teeth few and large [UOT 25–37 (median 31)]; dominant males light grey with a black head and a bright red anal fin.

Amongst piscivorous species from the Lake Edward system, H. aquila sp. nov. differs from H. latifrons sp. nov., H. mentatus , H. rex sp. nov., H. simba sp. nov., and H. glaucus sp. nov. by a larger eye [ED 30.0–31.5 (30.6) vs 22.2–29.9 (24.4–28.3) % HL].

It further differs from H. latifrons sp. nov. and H. mentatus by a shorter caudal peduncle [CPL 14.6–15.4 (15.0) vs 15.7–18.0 (16.6–17.0) % SL]; further from H. latifrons sp. nov. by the absence vs presence of a well-defined mid-lateral band; further from H. mentatus by dominant males uniformly light grey vs yellow-green with a red anterior part of flank.

It further differs from H. rex sp. nov. by a shallower lacrimal [LaD 17.0–19.1 (18.3) vs 18.9–22.5 (20.8) % HL] and dominant males light grey with black operculum and snout vs cream-coloured with an orange operculum and a light blue snout.

It further differs from H. simba sp. nov. by a larger number of scales between first anal-fin spine and upper lateral line (ULL-A 12–15, rarely 11 vs 9–11), an absent vs strongly developed mental prominence, and dominant males light grey with a black head vs uniformly yellow with an orange anterior part of flank.

It further differs from H. glaucus sp. nov. by a broader head [HW 40.1–43.7 (42.0) vs 38.9–40.9 (39.7) % HL] and dominant males light grey with bright red anal and caudal fins vs light blue with crimson anal and caudal fins.

It differs from H. kimondo sp. nov., H. falcatus sp. nov., H. curvidens sp. nov., H. pardus sp. nov., H. quasimodo sp. nov., and H. squamipinnis by the combination of large vs small outer oral teeth and smaller number of outer upper jaw teeth [UOT 25–37 (31) vs 39–79 (45–58)].

It further differs from H. kimondo sp. nov., H. falcatus sp. nov. and H. quasimodo sp. nov. by absence vs mostly presence of a well-defined mid-lateral band and dominant males light grey with a black head vs grey dorsally and yellow ventrally, olive-green with an orange-red anterior part of flank, or light grey dorsally and blue-black ventrally; further from H. kimondo sp. nov. by a narrower head [HW 40.1–43.7 (42.0) vs 42.9–48.0 (45.1) % HL].

It further differs from H. curvidens sp. nov. and H. pardus sp. nov. by a deeper cheek [ChD 26.8–30.8 (28.3) vs 20.8–24.9 (22.5–23.2) % HL]; further from H. pardus sp. nov. by dominant males light grey vs speckled to uniformly black.

It further differs from H. squamipinnis by larger eyes [ED 30.0–31.5 (30.6) vs 23.1–29.7 (26.6) % HL] and dominant males light grey vs slate blue.

Etymology

Specific name from the Latin ‘ aquila ’ for ‘eagle’; referring to predatory morphology and large eyes.

Material examined

Holotype UGANDA • ♂, 113.6 mm SL; Lake Edward, Kayanja offshore; 0°05′31.2″ S, 29°45′30.3″ E; 20 Jan. 2018; HIPE3 exped. leg.; RMCA 2018.008.P.0355 .

Paratypes UGANDA – Lake Edward • 1 ♀, 2 ♂♂, 83.9–117.7 mm SL; islands near Katwe ; 0°10′04.9″ S, 29°52′27.4″ E; 18 Jan. 2018; HIPE3 exped. leg.; RMCA 2018.008.P.0349 to 0351 • 1 ♀, 1 ♂, 108.7, 117.6 mm SL; islands near Katwe ; 0°10′04.9″ S, 29°52′27.4″ E; 19 Jan. 2018; HIPE3 exped. leg.; RMCA 2018.008.P.0352 to 0353 • 1 ♂, 85.6 mm SL; mouth of Kazinga Channel ; 0°12′34.8″ S, 29°53′01.5″ E; 19 Jan. 2018; HIPE3 exped. leg.; RMCA 2018.008.P.0354 • 1 ♂, 122.9 mm SL; 0°24′16.0″ S, 29°46′24.8″ E; 24 Jan. 2018; HIPE3 exped. leg.; bought at Rwenshama landing site; RMCA 2018.008.P.0356 .

Description

Based on 8 specimens (83.9–122.9 mm SL); body shallow ( Table 1 ) and oval ( Fig. 20 ). Head long, narrow, and with a straight to gently convex dorsal outline; interorbital area narrow; eye average in size in comparison to generalised H. elegans (but large for a piscivorous species); cheek deep; lacrimal average in depth. Snout average in length, rounded in dorsal view, narrow, relatively blunt, and slopes gently at 35–45°; premaxillary pedicel long and (strongly) prominent. Jaws isognathous to weakly prognathous, long, narrow, and rounded in dorsal view; gape large and slopes at 25–35°; maxilla extends to vertical through anterior margin of pupil. Lower jaw relatively stout and with straight ventral outline in lateral view, mental prominence absent or weakly developed, and lower jaw side nearly flat with an inclination of 25–35° to horizontal in anterior view. Upper jaw expanded anteriorly. Lips and oral mucosa relatively large. Neurocranium average in depth, ethmo-vomerine block decurved, preorbital region shallow (18–24% NL), orbital region average in depth (30–33% NL), and supraoccipital crest shallow and wedge-shaped ( Fig. 21b ).

Outer oral teeth few, unicuspid, and very large. Necks stout, conical, and straight; crowns straight to weakly recurved and acutely pointed. Dental arcades with anterior half expanded laterally. Outer teeth widely and irregularly set with neck-distances of 1–4 neck-widths. No enlarged teeth posterior in upper jaw. Inner teeth small, recurved, a mixture of unicuspid and weakly tricuspid, weakly tricuspid rare in large specimens (> 100 mm SL), and acutely pointed in all specimens. Tooth bands very slender crescent-shaped with 1–2 rows of inner teeth, and narrow posteriorly until only outer row remains past ¾ length of tooth band in upper jaw, past ⅔ length of tooth band in lower jaw. Inner teeth closely and regularly set on 1 outer neck-width from outer row; implantation recumbent; size uniform throughout tooth band.

Lower pharyngeal bone long, very narrow, slim, and shallow over whole length ( Fig. 22 ). Pharyngeal teeth relatively large and slender; major cusps acutely pointed; cusp gaps concave; minor cusps and cusp protuberances very small. Teeth in two median longitudinal rows equal in size and form to lateral teeth, 12 in each row. Posterior transverse row with 16–17 teeth, implanted erectly with a lateral inclination; major cusps nearly straight, bluntly pointed, and laterally compressed; minor cusps mostly absent.

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 caudal-fin base and two scales anterior to this vertical. Pectoral fin reaches to between genital opening and second anal-fin spine; pelvic fin reaches to genital opening in females, to between first and second anal-fin spines in males; first pelvic fin slightly elongated in all specimens.

Ceratobranchial gill rakers in outer row of first gill arch short, stout, and simple; posteriormost rakers anvil-shaped or bifid. Epibranchial gill rakers slender and simple.

Colouration in life

Dominant males: body metallic grey; dorsum greyish; belly speckled black; chest, cheek, snout, lower jaw, and lips black; eye with (dark) grey outer ring and golden inner ring ( Fig. 21c ). Nostril, interorbital, and lacrimal stripes very faint. Pectoral fin hyaline, pelvic fin black; dorsal fin sooty and with black lappets; anal and caudal fins bright red and with dusky bases; anal fin with dusky posterior part and 1–2 large orange egg-spots with dusky rings.

Females and juveniles: body and dorsal part of head silver with yellowish sheen; belly, chest, operculum, cheek, lower jaw, and lips white; snout dusky; eye with (dark) grey outer ring and silver inner ring ( Fig. 21d ). Nostril and interorbital stripes faint. Pectoral fin hyaline, pelvic fin white; dorsal and caudal fins dusky; dorsal fin with black lappets; caudal fin with a yellowish base and a faint red distal part; anal fin yellow with a red sheen.

Preserved colouration

Body brown; dorsum dark-brown; ventral part of body and operculum yellowish; chest and lower jaw black in males; cheek yellowish in females, dark-brown in males; snout dusky ( Fig. 21a ). Nostril and interorbital stripes faint; lacrimal stripe narrow and well-defined; mental blotch present; vertical preopercular stripe well-defined in males. Pectoral fin hyaline; pelvic fin yellowish with blackish first rays in females, black in males; dorsal fin dusky and with black lappets and maculated posterior part; anal fin yellowish with a dusky overlay and, in males, with black lappets and 1–2 large egg spots; caudal fin with a dusky base, a hyaline distal part, and, in males, whole ventral half hyaline.

Distribution and ecology

Only known from Lake Edward, found in inshore areas over muddy 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. 20. Haplochromis aquila sp. nov., holotype, ♂, 113.6 mm SL (RMCA 2018.008.P.0355). Drawn by N. Vranken.

Fig. 21. Haplochromis aquila sp. nov. a. Photograph of preserved holotype (RMCA 2018.008.P.0355; 113.6 mm SL). b. X-ray image of holotype. c–d. Photographs of freshly caught specimens. c. Dominant male, the holotype. d. Female (RMCA 2018.008.P.0352; 108.7 mm SL) to illustrate the live colour patterns. The contrast was slightly enhanced.

Fig. 22. Haplochromis aquila sp. nov. (RMCA 2018.008.P.0356; 122.9 mm SL). a. Dorsal view of the lower pharyngeal jaw. b. Lateral view of the lower pharyngeal jaw.