Haplochromis curvidens, 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 : 53-58

Haplochromis curvidens sp. nov.

urn:lsid:zoobank.org:act:E11E39DC-0085-4CB5-9E4C-E3EA0C11216F

Figs 1–2 , 29–31 ; Table 1

Differential diagnosis

Species with a piscivorous morphology; outer oral teeth many, small, and (strongly) recurved [UOT 45–60 (median 49)]; non-dominant males dusky green with a blue sheen and 5–7 (faint) vertical stripes.

Amongst piscivorous species from the Lake Edward system, H. curvidens sp. nov. differs from H. latifrons sp. nov., H. mentatus , H. rex sp. nov., H. simba sp. nov., H. glaucus sp. nov., and H. aquila sp. nov. by small vs large outer oral teeth and a larger number of outer upper jaw teeth [UOT 45–60 (49) vs 22–47 (27–36)]; further from H. latifrons sp. nov., H. mentatus , H. rex sp. nov., H. simba sp. nov., and H. glaucus sp. nov. by a shallower lacrimal [LaD 16.0–17.8 (mean 16.7) vs 18.0–23.0 (19.5–20.8) % HL]; further from H. rex sp. nov., H. simba sp. nov., H. glaucus sp. nov., and H. aquila sp. nov. by a shallower cheek [ChD 22.4–24.9 (23.2) vs 26.2–33.5 (28.3–31.1) % HL].

It differs from H. kimondo sp. nov., H. falcatus sp. nov., and H. quasimodo sp. nov. by the combination of a shallower cheek [ChD 22.4–24.9 (23.2) vs 24.8–35.2 (exceptionally 23.3 and 23.7 in one specimen of H. falcatus sp. nov. and H. quasimodo sp. nov., respectively) (means 26.0–30.9) % HL] and absence vs presence of a well-defined mid-lateral band; further from H. kimondo sp. nov. by narrower jaws [LJW 38.5–43.2 (40.8) vs 44.7–53.3 (49.3) % LJL]; further from H. falcatus sp. nov. by a shorter pre-dorsal distance [PrD 34.5–37.9 (36.3) vs 38.2–41.1 (exceptionally 36.9 in one specimen) (mean 39.5) % SL]; further from H. quasimodo sp. nov. by a shallower body [BD 29.0–32.0 (30.8) vs 33.5–41.7 (37.4) % SL].

It differs from H. pardus sp. nov. by the combination of a shorter anal fin base [AFB 17.9–18.6 (18.3) vs 19.2–22.2 (20.5) % SL], a slightly broader interorbital area [IOW 46.4–52.5 (49.1) vs 39.3–48.4 (43.9) % HW], and all specimens faint yellow to dusky green vs speckled to uniformly black.

It differs from H. squamipinnis sp. nov. by the combination of a shallower body [BD 29.0–32.0 (30.8) vs 32.4–39.3 (35.7) % SL], a shallower cheek [ChD 22.4–24.9 (23.2) vs 24.9–36.0 (29.0) % HL], and absence vs presence of minute scales on proximal parts of dorsal and anal fins.

Etymology

Specific name from the Latin ‘ curvus ’ for ‘curvature’, and ‘ dentatus ’ for ‘tooth’; referring to strongly recurved oral teeth.

Material examined

Holotype UGANDA • ♂, 112.0 mm SL; Lake Edward; 0°24′16.0″ S, 29°46′24.8″ E; 9 Nov. 2016; HIPE1 exped. leg.; bought at Rwenshama landing site; RMCA 2016.035.P.0219 .

Paratypes UGANDA – Lake Edward • 1 ♂, 94.8 mm SL; ‘Coral Reef’, hard substrate at mouth of Nyamugasani river ; 0°10′08.4″ S, 29°49′37.2″ E; 21 Oct. 2016; HIPE1 exped. leg.; RMCA 2016.035.P.0215 • 2 ♂♂, 1 ♀, 91.2–102.5 mm SL; Mukutu Kihinga, rocky offshore of Mweya ; 0°11′31.2″ S, 29°52′26.4″ E; 23 Oct. 2016; HIPE1 exped. leg.; RMCA 2016.035.P.0216 to 0218 • 1 ♀, 90.2 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.0340 • 1 ♂, 101.1 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.0341 • 1 ♀, 92.3 mm SL, no morphometrics taken; islands near Katwe ; 0°10′04.9″ S, 29°52′27.4″ E; 18 Jan. 2018; HIPE3 exped. leg.; IRSNB 919 .

Description

Based on 8 specimens (90.2–112.0 mm SL); body shallow ( Table 1 ) and oval ( Fig. 29 ). Head long, narrow, and with a straight to very gently convex dorsal outline; eye and interorbital area average in width; cheek and lacrimal average in depth. Snout average in length, narrow, acute, and slopes gently at 35–45°; premaxillary pedicel long and strongly prominent. Jaws isognathous to weakly prognathous, long, slim, very narrow, and rounded in dorsal view; gape large and slopes gently at 15–30°; maxilla (almost) extends to vertical through anterior point of pupil. Lower jaw shallow and with a straight ventral outline in lateral view, mental prominence absent, and lower jaw side nearly flat with an inclination of 20–30° to horizontal in anterior view. Upper jaw weakly expanded anteriorly. Lips and oral mucosa thin. Neurocranium shallow, ethmo-vomerine block decurved, preorbital region very shallow (19–21% NL), orbital region shallow (28–31% NL), and supraoccipital crest shallow and wedge-shaped ( Fig. 30b ).

Outer oral teeth numerous, unicuspid, and small. Necks slender, cylindrical to conical, and weakly recurved; crowns recurved and acutely pointed. Dental arcades rounded. Outer teeth closely and regularly set with neck-distances of ½ neck-width. In upper jaw, 1–3 posteriormost teeth enlarged. Inner teeth small, strongly recurved, unicuspid, and acutely pointed. Tooth bands very slender crescent-shaped with 1–2 rows of inner teeth, and narrow posteriorly until only outer row remains past ⅔ lengths of tooth bands. Inner teeth closely and regularly set on ½–1 neck-width from outer row in lower jaw, on 1–2 neck-widths from outer row in upper jaw; implantation recumbent; size uniform throughout tooth band.

Lower pharyngeal bone average in length, narrow, slim, and shallow with a slightly deeper keel ( Fig. 31 ). Pharyngeal teeth relatively large and slender; major cusps acutely pointed; cusp gaps straight; minor cusps and cusp protuberances very small. Teeth in two median longitudinal rows equal in size and form to lateral teeth, 10–11 in each row. Posterior transverse row with 20–22 teeth, implanted erectly with a lateral inclination; major cusps weakly recurved, 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 and pelvic fins reach to anal opening, pelvic fin reaches to first anal-fin spine in males; first branched pelvic-fin ray elongated in all specimens.

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

Colouration in life

Dominant males: colour pattern unknown. Non-dominant males: based on pictures of two recently deceased specimens ( Fig. 30c ). Dorsal half of body dusky greenish; ventral half of body faint yellow; transition gradual; flank with blue sheen and 5–7 vertical stripes; belly, chest, and cheek whitish; operculum yellowish; snout dusky; eye with (dark) grey outer ring and silver inner ring. Nostril and lacrimal stripes and nape band present; interorbital and supraorbital stripes faint. Pectoral fin yellowish; pelvic fin black; dorsal fin dusky and with black lappets; anal fin faint orange and with 1–3 relatively large, yellow egg-spots with dusky rings; caudal fin dusky.

Females and juveniles: body faint yellow with a greenish dorsum; belly and chest white; snout dusky; eye with (dark) grey outer ring and silver inner ring ( Fig. 30d ). Nostril, interorbital, supraorbital, and lacrimal stripes and mental blotch faint. Pectoral and pelvic fin yellowish; dorsal fin dusky and with black lappets; anal fin yellowish and with 2 spots resembling egg-spots; caudal fin dusky.

Preserved colouration

Body brown; dorsum dark brown; chest and belly white; cheek and operculum yellowish; snout dusky ( Fig. 30a ). Flank with 5–7 (faint) vertical stripes. Nostril and lacrimal stripes and mental blotch present; interorbital and supraorbital stripes faint. Pectoral fin hyaline; pelvic fin yellowish with black first rays in females, black in males; dorsal and caudal fins dusky; dorsal fin with black lappets and posterior sooty part; caudal fin with maculated dorsal part; anal fin yellowish and with dusky distal margin and 1–3 relatively large egg-spots.

Distribution and ecology

Only known from Lake Edward, found 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. 29. Haplochromis curvidens sp. nov., holotype, ♂, 112.0 mm SL (RMCA 2016.035.P.0219). Drawn by N. Vranken.

Fig. 30. Haplochromis curvidenssp. nov. a. Photograph of preserved holotype (RMCA 2016.035.P.0219; 112.0 mm SL). b. X-ray image of holotype. c–d. Photographs of freshly caught specimens. c. Holotype, an adult male. d. Female (RMCA 2018.008.P.0340); 90.2 mm SL) to illustrate the live colour patterns. The contrast was slightly enhanced.

Fig. 31. Haplochromis curvidens sp. nov. (RMCA 2016.035.P.0217; 102.5 mm SL). a. Dorsal view of the lower pharyngeal jaw. b. Lateral view of the lower pharyngeal jaw.