Lamprologus congoensis Schilthuis, 1891

SCHELLY, ROBERT C. & STIASSNY, MELANIE L. J., 2004, Revision of the Congo River Lamprologus Schilthuis, 1891 (Teleostei: Cichlidae), with Descriptions of Two New Species, American Museum Novitates 3451, pp. 1-40 : 5-11

Lamprologus congoensis Schilthuis, 1891

Figures 5–8 , Table 1,

Plate 1a

Acanthochromis seminudus Vaillant, 1886: 18 (nomen nudum) (Type locality: Nganchou).

Lamprologus congoensis Schilthuis, 1891: 85 , fig. 1 (Type locality: Kinshasa, Stanley Pool ).

Lamprologus congolensis: Boulenger, 1901: 402 .

Lamprologus fuscus Pellegrin, 1927: 52 (Type locality: Bolobo).

LECTOTYPE: BMNH 1891.12.29.10 , Kinshasa, 4 ° 15 ̍ 2 ̎ S, 15 ° 25 ̍ 0 ̎ E, A. Greshoff. (This specimen is here designated the lectotype as it is the largest of the remaining syntypes; BMNH 1899.9.6.1, the largest syntype, is lost.)

PARALECTOTYPE: BMNH 1891.12.29.11 , collected with lectotype.

ADDITIONAL MATERIAL EXAMINED: 91 specimens. Bolobo (02 ° 09 ̍ S, 16 ° 14 ̍ E) MRAC 19711 (Holotype of Lamprologus fuscus Pellegrin, 1927), H. Schouteden ; MRAC 175060, 1/1/1956 – 12/31/1956. N’Kele; Kasai River, Makaw (03 ° 28 ̍ S, 18 ° 18 ̍ E) MRAC 153440, 1/1/1954 – 12/31/1954, E. Jans. Kasai River, Bokoni (03 ° 9 ̍ S, 17 ° 10 ̍ E) AMNH 233570 (n = 2), 9/17/2002, C. Shumway et al. Kinshasa (Léopoldville) (04 ° 18 ̍ S, 15 ° 18 ̍ E) MRAC 17483–17484 (1 specimen c&s), H. Schouteden ; MRAC 39576, 1/1/1934 – 3/16/1934, A. Tinant ; MRAC 39624, 1/1/1934 – 4/3/1934, A. Tinant ; MRAC 40950–40951, 1/1/1934 – 4/24/ 1934, A. Tinant ; MRAC 41004–41005, 1/1/ 1934 – 4/24/1934, A. Tinant ; MRAC 43983, 1/1/1935 – 12/16/1935, A. Tinant ; MRAC 55231–55232, 1/1/1937 – 12/31/1937, A. Tinant ; MRAC 76060.0116, 10/19/1960, P. Brichard ; MRAC 77346–77347, 1/1/1951 – 12/ 31/1951, A. Dubois ; MRAC 78144, 1/1/ 1951 – 12/31/1951, M.H. Pierret ; MRAC 94009.0001–94009.0005, 1/1/1993 – 12/31/ 1993, W. van der Elst ; MRAC 177669, 1/1/ 1967 – 12/31/1967, P. Brichard ; AMNH 233613 (n = 13, 11 c&s), aquarium trade specimens from Kinshasa region, 10/27/ 2003. Léopoldville, Kalina (04 ° 18 ̍ S, 15 ° 16 ̍ E) MRAC 67426, 6/1/1945 – 6/30/ 1945, J.M. Berteaux. Stanley Pool (04 ° 06 ̍ S, 15 ° 15 ̍ E // 04 ° 20 ̍ S, 15 ° 23 ̍ E) MRAC 88001.2808–88001.2841, 1/1/1957 – 12/31/ 1957, Brien, Poll, & Bouillon ; MRAC 94314–94317, 1/1/1954 – 5/31/1954, Dubois & Dubois ; MRAC 88001.2807, Stanley Pool, Stat. 5, Bamu archipelago, 04 ° 14 ̍ S, 15 ° 22 ̍ E, 9/9/1957, Brien, Poll, & Bouillon ; MRAC 118140–118154 (3 specimens c&s), Stanley Pool, Stat. 33, channel in front of Maluku, 04 ° 04 ̍ S, 15 ° 33 ̍ E, 10/4/1957, Brien, Poll, & Bouillon. Monsembe, upper Congo (01 ° 08 ̍ N, 18 ° 32 ̍ E) BMNH 1896.3.9.13–14 (1 specimen c&s), Rev’d. J.H. Weeks ; BMNH 1898.7.9.15, Rev’d. J.H. Weeks. Nganchou, Congo (03 ° 20 ̍ S, 16 ° 12 ̍ E) MNHN 1886.442–445 (Syntypes of Acanthochromis seminudus Vaillant, 1886 ), Savorgnan de Brazza. Sangha River, Bayonga, Doli Lodge, by sand island in middle of channel, Central African Republic (02 ° 55 ̍ N, 16 ° 15 ̍ E) AMNH 227439 (n = 1), 6/10/1998, J. Sullivan & J. Kindimoungo. Locality unknown: MRAC 183617–183620, W. Wickler.

DIFFERENTIAL DIAGNOSIS: Lamprologus congoensis is distinguished from L. lethops and L. symoensi by its regularly imbricating, large, uniformly sized flank scales. It is distinguished from L. mocquardi by an elevated supraoccipital crest, presence of a single supraneural, and uniformly dark pigment around the exposed margin of the flank scales, giving the appearance of chain mail. Lamprologus congoensis and L. tumbanus are similarly deep bodied and share a similar flank pigmentation pattern, but L. congoensis differs from L. tumbanus in having 32–35 lateral line scales (vs. 29–31 in L. tumbanus ), a shorter HL as a percentage of SL (31.3– 34.6% vs. 34.6–37.0% in L. tumbanus ), and five sensory pore openings on the lachrymal instead of four. While L. congoensis has long pelvic fins reaching beyond the anal fin origin and a strongly interdigitating LPJ ventral suture, both L. werneri and L. teugelsi , n.sp., have short pelvic fins that rarely or never reach the anus and minimal or no interdigitation at the LPJ ventral suture. While L. congoensis shares with L. tigripictilis , n.sp., relatively produced pelvic fins and a strongly interdigitating LPJ ventral suture, L. congoensis has 5–6 rather than the 9–10 dark bars on the flanks of L. tigripictilis , n.sp. Additionally, L. congoensis has an elevated supraoccipital crest while L. tigripictilis , n.sp., has a low crest, and almost without exception has fewer vertebrae (30–31 vs. 31–33) and lateral line scales (32–35 vs. 35–37) than L. tigripictilis , n.sp.

DESCRIPTION: Counts and measurements for 20 specimens, including lectotype and paralectotype, are given in table 1. Among the more deep­bodied fluviatile species of Lamprologus (body depth 21.0–27.8%, mean 25.2% SL), especially so as adults. Greatest body depth at about base of second or third dorsal fin spine. Head length 31.3–34.6%, mean 32.8% SL. In smaller individuals, head profile rises at an angle of about 40 °. In larger individuals, profile rises more steeply, at an angle of about 50 ° from tip of snout to top of orbit. Dorsal body profile convex, curving gently downward along length of dorsal fin to caudal peduncle; ventral body profile somewhat rounded posteriorly, curving gently upward anterior to caudal peduncle. Species sexually dimorphic, with adult males displaying well­developed, fat­filled nuchal hump (resulting in slight concavity of dorsal head profile anterior to the nuchal hump). Males also attain larger size (largest male 104.3 mm, largest female 75.0 mm), and have somewhat longer dorsal, anal, and pelvic fins than females.

Fins: Dorsal fin XVII–XIX (mode XIX) 6–9. Anal fin V–VII (mode VI) 5–7 (mode 6). Spines in both fins gradually increasing in length posteriorly. Dorsal and anal fins with tapering filamentous extensions reaching to about midlevel of caudal fin. Caudal fin large, rounded, and paddle­shaped, with 14 branched rays; often appears lanceshaped, subacuminate in preserved specimens or when adducted. Pectoral fins short, not reaching vertical through anus. Pelvic fins in all but smallest individuals elongate, with tapering ends reaching or extending just beyond anal fin origin (pelvic fin length 19.7–30.4%, mean 24.8% SL). Second ray of pelvic fin longest in fin in both sexes.

Teeth: Jaws isognathous, with both outer and inner row teeth unicuspid and sharply pointed. Single series of 6–8 greatly enlarged, recurved, procumbent canines situated anteriorly, with largest teeth furthest from symphysis. Inner teeth in 6–8 poorly defined rows of tightly packed, small, recurved caniniform teeth anteriorly, gradually thinning along length of jaw to 1 or 2 rows posteriorly. Lateral­most tooth row slightly enlarged and extending almost entire length of dentary and premaxilla.

Gill Rakers: Relatively slender, elongate, non­denticulate. Gill rakers number 6–9 (typically 7) along hypobranchial and ceratobranchial of first gill arch, with a single raker positioned in angle of arch in most cases. Two to 5 (typically 3) rakers along epibranchial of first gill arch.

Lower Pharyngeal Jaw (fig. 6): Wider than long, strongly interdigitating along ventral suture. Usually 25–28 teeth in most posterior tooth row. Medial teeth enlarged and more or less molariform; lateral teeth slender and either beveled or bluntly hooked.

Scales: Flank scales ctenoid, of uniform size. Lateral line scales 32–35. Upper and lower branches of lateral line not overlapping. Cheek naked; opercle and subopercle partially scaled. Gradual transition to small scales on belly and above lateral line near dorsal fin origin, with small, embedded scales extending beyond dorsal fin origin onto nape. Dorsal and anal fins scaleless. Small scales occur over most of caudal fin.

Vertebrae: 30–31; 14 + 16 (6), 14 + 17 (7).

Additional Osteology (fig. 7): Infraorbital series comprised of broad, platelike lachrymal with 5 sensory canal openings, and 2–3 tubular infraorbitals adjacent to lachrymal. Dermosphenotic absent. Single supraneural present. Supraoccipital crest elevated, and extends anteriorly as low frontal ridge to median coronal pore (NLF0). In larger specimens, elongate, paired, clublike processes on supraoccipital crest serve as attachment areas for supracarinalis anterior tendons.

Coloration: In life, base body coloration grayish lavender, with shades of yellow on belly, posterior to base of pectoral fin, along junction of preopercle and opercle, and around ventral margin of orbit. Dark, scaleless opercular spot present. Five or six somewhat dark vertical bars along flanks usually present. Individual flank scales with dark pigment distributed uniformly around exposed posterior margin, creating intersecting rows of thin, oblique bands of pigment that present appearance of chain­link fence or chain mail. Small, whitish maculae along interspinous membrane and between rays of dorsal, anal, and caudal fins. Dorsal, anal, and caudal fins with oblique black striations. Adult males with iridescent spots in posterior field of most flank scales; each spot situated adjacent to the overlapping edge of the preceding scale. Preserved coloration yellowish brown, fading to uniform dull brown in very old specimens, with scale pigmentation often completely lost.

DIET: Gut short and simple, with a length of about 50% of SL. Gut contents included fragments of insects and a spider.

DISTRIBUTION (fig. 8): Congo River mainstream from Malebo Pool to Monsembe (just upstream of the confluence of Congo and Lulonga Rivers); collections have also been made from the lower Kasai River and from the upper Sangha River in southwestern Central African Republic. Given the major gaps between the main channel Congo River collection localities and the occurrence of the species in the upper Sangha, it appears that L. congoensis remains unsampled from a large portion of its range.

REMARKS: Considering that L. congoensis is fairly common in the aquarium trade centered on the Kinshasa region, the number of specimens in museum collections is surprisingly small. In addition to being the largest species, and the only one in which males develop a nuccal hump, L. congoensis is distinctive among the Congo River Lamprologus in having fully molariform teeth along the symphysis of the LPJ (fig. 6a).

Figures

Plate 1. (a) Lamprologus congoensis, MRAC 118140–53, male, 104 mm SL; (b) Lamprologus tumbanus, MRAC 100851–53, male, 51 mm SL; (c) Lamprologus mocquardi, AMNH 5897, male, 78 mm SL; (d) Lamprologus werneri, MRAC 98158–92, male, 56 mm SL.

Fig. 5. Lamprologus congoensis, male, 100 mm TL, modified from Boulenger (1915).

Fig. 6. Lower pharyngeal jaw of Lamprologus congoensis MRAC 78144: (a) dorsal view, showing medial molariform teeth; (b) ventral view, showing interdigitating suture.

Fig. 7. Lamprologus congoensis, MRAC 118154: (a) neurocranium, first vertebra, and supraneural; (b) lachrymal and adjacent infraorbitals.

Fig. 8. Collection localities of Lamprologus congoensis.