Labeotropheus obscurus, Phiri and Pauers, 2023

Pauers, Michael J. & Phiri, Titus B., 2023, Six New Species of Labeotropheus (Cichliformes: Cichlidae) from the Malaŵian Shore of Lake Malaŵi, Africa, Ichthyology & Herpetology 111 (2), pp. 263-292 : 284-287

Labeotropheus obscurus, Phiri and Pauers , new species

urn:lsid:zoobank.org:act:EC803C63-127B-43AE-AD0F- 8A73A1DDD6DB

Figures 3 , 4 , 12 ; Tables 4, 5 , 13

Holotype.— SAIAB 211380, adult male, 78.2 mm SL, Malaŵi, Lake Malaŵi, Namalenje Island, –13.730081, 34.641074, Michael J. Pauers, Titus B. Phiri, and Sanudi Likupe, 15 January 2020.

Paratypes.— FMNH 145013, 1 male, 78.3 mm SL, 1 female, 75.6 mm SL, Malaŵi, Lake Malaŵi, Namalenje Island, –13.730081, 34.641074, Michael J. Pauers, Titus B. Phiri, and Sanudi Likupe, 15 January 2020; MPM Fi50080, 1 male, 68.1 mm SL, 3 females, 63.6, 66.6, and 67.2 mm SL, Malaŵi, Lake Malaŵi, Namalenje Island, –13.730081, 34.641074, Michael J. Pauers, Titus B. Phiri, and Sanudi Likupe, 15 January 2020; MPM Fi50091, 2 males, 5 females, 64.0–70.2 mm SL, Malaŵi, Lake Malaŵi, Namalenje Island, –13.730788, 34.640388, Michael J. Pauers, Titus B. Phiri, and Sanudi Likupe, 17 January 2020; MPM Fi50091, 1 male, 4 females, 65.9–71.8 mm SL, Malaŵi, Lake Malaŵi, Namalenje Island, –13.729377, 34.640478, Michael J. Pauers, Titus B. Phiri, and Sanudi Likupe, 17 January 2020; SAIAB 211381, 1 male, 66.1 mm SL, 1 female, 51.4 mm SL, Malaŵi, Lake Malaŵi, Namalenje Island, –13.730081, 34.641074, Michael J. Pauers, Titus B. Phiri, and Sanudi Likupe, 17 January 2020.

Diagnosis.— Labeotropheus obscurus differs from all other species of Labeotropheus due to the unusually drab and muted coloration of sexually mature males; male nuptial color pattern dominated by gray and brown pigmentation, with some blue and orange highlights on scales and fins, as opposed to a nuptial color pattern dominated by blue, orange, or red pigmentation.

Labeotropheus obscurus differs from the slender-bodied Labeotropheus , L. trewavasae , L. simoneae , and L. chirangali , but not L. rubidorsalis , new species, due to its greater body depth (35.2–41.5% SL vs. 26.3–33.4% in L. trewavasae ; 26.9– 30.8% in L. simoneae ; and 26.6–33.2% in L. chirangali ). Labeotropheus obscurus typically has a greater body depth than L. rubidorsalis , new species, although the ranges slightly overlap (31.6–36.1% SL in L. rubidorsalis , new species). Overall, L. obscurus does have a deeper body than L. rubidorsalis , new species, as indicated by several other measurements akin to body depth, including the distance between the origin of the dorsal fin and the origin of the anal fin (50.8–56.3% SL vs. 45.6–50.3%), the distance between the insertion of the dorsal fin and the insertion of the anal fin (15.8–17.8% SL vs. 13.5–15.7%), the distance between the insertion of the dorsal fin and the origin of the anal fin (30.3– 33.2% vs. 27.6–30.3%), and the distance between the origin of the dorsal fin and the attachment of the pelvic fins (35.4– 40.5% SL vs. 31.5–35.4%).

Labeotropheus obscurus has a distinctly larger eye diameter than several of the robust species of Labeotropheus (27.3– 32.4% HL vs. 23.7–26.6% in L. fuelleborni ; 22.6–25.5% in L. chlorosiglos ; and 24.9–27.5% in L. alticodia ). It also has fewer rows of teeth in the upper jaw than all robust Labeotropheus except L. alticodia (3–4 vs. 4–5 in L. fuelleborni ; 5–7 in L. chlorosiglos ; 5–8 in L. artatorostris ; 4–6 in L. aurantinfra ; and 4– 6 in L. candipygia ), and fewer teeth in the left side of the lower jaw (20–26) than L. fuelleborni (31–43), L. chlorosiglos (30–37), and L. alticodia (29–35).

Description.— Morphometric and meristic data summarized in Table 13. Body compressiform; body shape ovoid. Body depth 35.2–41.5% SL and consistently deep throughout trunk. Body relatively narrow at pectoral fin and opercular tab. Scales on belly and anterior abdomen cycloid and tightly crowded. Flank scales ctenoid; exposed portion of scale fan-shaped and approximately hexagonal. Anterior lateral line overlapping posterior lateral by 0–4 scales. Dorsal fin 56.1– 63.0% SL, 16–18 spines and 7–9 rays. Origin of dorsal fin overlapping opercular tab. Dorsal-fin rays 3, 4, 5 long, reaching to hypural and beyond to caudal fin. Anal-fin shape variable; angular and kite-like in some (6 of 19) specimens, angled anteriorly with slight rounding to membrane posteriorly in others (13 of 19). Origin of anal fin opposite dorsal-fin spine 16 in majority of specimens; insertion of anal fin variable (anterior, opposite, or posterior) with respect to insertion of dorsal fin. Anal-fin rays 3, 4, 5 reach past hypural in most males; these only reach to mid-caudal peduncle in females. Caudal fin subtruncate. Pectoral fin long (22.8–28.3% SL), rounded, with 13–15 rays. Pelvic fin long, minimally reaching origin of anal fin and longer in the majority of specimens. Pelvic-fin ray slightly produced and filamentous in all males and most females; pelvic-fin ray is non-filamentous in some females. Pelvic-fin attachment opposite dorsal-fin spine 5 or 6 in most specimens; opposite dorsal-fin spine 4 in one specimen.

Head long (29.2–37.8% SL), depth typical for Labeotropheus . Head profile moderately to strongly curved with slightly protruding snout. Snout long but narrow; snout width 30.9–44.6% HL with slight snout pad (9.5–19.4% HL). Cheek with 3–4 scale rows. Infraorbital pores 9, with 22–46 neuromasts among them. Oral jaws long and narrow. Oral teeth tricuspid and closely set on both upper and lower jaws; 4–10 tricuspid teeth on lateral portion of left upper jaw. Gill rakers stout, triangular, and widely spaced; 6–11 ceratobranchial and 1–3 epibranchial gill rakers on first gill arch. All specimens with 1 raker between the cerato- and epibranchial rakers.

Coloration of males.— Ground color of head, operculum, flank, and caudal peduncle gray. Flank suffused with pale blue in some individuals; 11 darker bars extending across flank and peduncle visible in some individuals. Scales of flank abdominal to lateral line, between operculum and caudal peduncle, with orange spots near insertion of scale. Opercular tab black, overlain with metallic blue in some individuals. Dorsal fin gray in most individuals, pale blue in males with pale blue flanks; dorsal fin with orange tips and thin orange trailing edge in all individuals. Caudal fin gray with orange trailing edge. Anal fin predominantly gray with orange pigment on spinous portion; rayed portion with yellow tips and trailing edge, 2–4 orange-yellow eggspots present. Pelvic fin orange with white leading edge.

Preserved males uniformly brown or dark gray with 11 dark bars spanning flank and caudal peduncle visible on some individuals.

Coloration of females.— Head, body, and caudal peduncle uniformly light gray, with 11 faint dark bars extending across flank and caudal peduncle; some individuals suffused with a faint metallic green. Scales of flank and caudal peduncle with small orange spots close to insertion of scale. Opercular tab black. Throat and branchiostegals white. Dorsal fin white with orange tips; some specimens with orange trailing edge. Caudal fin brownish gray, some specimens with orange trailing edge. Rayed portion of anal fin pale brownish gray with 1–2 yellow eggspots; spinous portion white. Pelvic fin pale orange, with bright white leading edge.

In preservative, females uniformly dark brown or gray with 11 faint vertical bars visible across flank and caudal peduncle on some specimens.

Multivariate analyses.— Due to the overlap of morphometric and meristic characteristics between L. obscurus and the other Labeotropheus , we compared the body depth–standard length ratios of L. obscurus and its geographically proximate congeners ( Fig. 3 ). This ratio clearly places L. obscurus with the robust Labeotropheus , and distinguishes it from L. trewavasae and L. rubidorsalis , new species ( Table 4). We also performed canonical discriminant function analyses on the meristic and Log 10 -transformed morphometric data of L. alticodia , L. artatorostris , L. fuelleborni , and L. obscurus . Both the morphometric and meristic canonical discriminant function analyses were robust and produced statistically significant results ( Table 5 ). Labeotropheus obscurus is distinct from L. artatorostris along the first morphometric canonical function and the first meristic canonical function ( Fig. 4 ). It is additionally distinct from L. alticodia and L. fuelleborni along the second meristic canonical function ( Fig. 4 ).

Distribution and abundance.— Labeotropheus obscurus is endemic to the Malaŵian shore of Lake Malaŵi, and is only known from Namalenje Island. Recently, it was reported that all Labeotropheus were possibly extirpated from Namalenje Island, as survey teams had not reported any occurrences of this genus at Namalenje Island for some time (TBP, pers. obs.). While we did both capture and observe Labeotropheus at Namalenje Island, females and juveniles were obvious and plentiful in the shallow regions, but males were found in deeper waters and were comparatively rare.

Etymology.— The specific epithet is the masculine form of the Latin adjective obscurus , meaning dark, dusky, or shadowy, in reference to the muted and mostly gray male nuptial color pattern, which is unusual for a species of Labeotropheus .

Figures

FIG. 3. Body depth–standard length relationships among L. fuelleborni, L. trewavasae, and the three new species of Labeotropheus from the southwestern portion of Lake Malaŵi. The ANOVA accompanying these data is in Table 4.

FIG. 4. Canonical function plots for robust Labeotropheus from the southwestern portion of Lake Malaŵi. (A) Morphometric canonical function 1 vs. meristic function 2; (B) meristic canonical function 1 vs. meristic function 2.

FIG. 12. Labeotropheus obscurus, new species. (A) Live male holotype (SAIAB 211380), 78.2 mm SL; (B) holotype after preservation; (C) live female paratype (FMNH 145013), 75.6 mm SL; (D) live male paratype (FMNH 145013), 78.3 mm SL, displaying a primarily blue color pattern.