Tilapia konkourensis, Dunz, Andreas R. & Schliewen, Ulrich K., 2012

Dunz, Andreas R. & Schliewen, Ulrich K., 2012, Description of a rheophilic Tilapia species Smith, 1840 (Teleostei: Cichlidae) from Guinea with comments on Tilapia rheophila Daget, 1962, Zootaxa 3314, pp. 17-30 : 21-26

Tilapia konkourensis , new species

( Fig. 3A –C, Table 3 )

Holotype: MRAC 81-20-P-51 (85.1 mm SL), Guinea, route Korela-Kondoya, River Konkouré (10° 32' N, 12° 52' W), P. De Kimpe, 10 Mar. 1981.

Paratypes: MRAC 81-20-P-52 (1, 68.7 mm SL), same data as holotype. MNHN 1987-1502 (1, 77.0 mm SL), Guinea, River Kakrima by Koussi, C. Lévêque, 15 Feb. 1982.

Differential diagnosis. Tilapia konkourensis sp. nov. differs from all other Tilapia sensu lato except T. fusiforme in a shallower body 30.0–31.5% vs. 32.9–52.5% SL and from T. fusiforme in having eight instead nine– twelve lower lateral line scales. It differs from all Tilapia sensu lato except T. rheophila by additional morphological and meristic characters: stout teeth in oral jaw vs. spatulate teeth in T. mariae (Boulenger, 1899) and T. cabrae Boulenger, 1899 ; median pharyngeal teeth of lower pharyngeal jaw never broadened with crest-like cusps as in T. cessiana Thys van den Audenaerde, 1968 and T. buttikoferi ; posterior pharyngeal teeth of lower pharyngeal jaw never clearly bicuspid as in T. busumana (Günther, 1903) , T. pra Dunz & Schliewen 2010 , T. brevimanus Boulenger, 1911 , T. sparrmanii Smith, 1840 , T. baloni Trewavas & Stewart, 1975 , T. ruweti (Poll & Thys van den Audenaerde, 1965) and T. guinasana Trewavas, 1936 ; vertical bars broader not than lighter interspaces; possessing slender to spatulate teeth in oral jaws as in T. joka Thys van den Audenaerde, 1969; no densely scaled caudal fin. Compared to T. congica , T. tholloni and T. bilineata , it further differs from all Tilapia (Coptodon) (excluding T. rheophila ) by a combination of the meristic characters: number of dorsal-fin spines (16 vs. 13–17) and rays (11 vs. 10–13), number of scales on the upper (21 vs. 17–23) and lower later line (8 vs. 7–14), and number of gill rakers (7–9 vs. 7–12) on first ceratobranchial (excluding gill rakers on cartilaginous plague). It differs from T. rheophila by a smaller eye diameter (7.5–7.6% vs. 8.0–10.7% SL), a shorter predorsal distance (31.1–33.6% vs. 34.2–38.2% SL), a longer length of the base of dorsal fin (61.4–62.3% vs. 56.9–60.9% SL) and a shorter pectoral fin length (22.2–24.0% vs. 25.1–28.3% SL).

It differs from the Tilapia related species Chilochromis duponti Boulenger, 1902 (for haplotilapiine intrarelationships see Schwarzer et al. 2009) in no densely scaled caudal fin or comb-like, spatulate teeth (Stiassny 2009); from Gobiocichla Kanazawa, 1951 in having two unconnected lateral lines vs. one continuous lateral line, and from Steatocranus Boulenger, 1899 (currently including the unrelated “ Steatocranus ” irvinei (Trewavas, 1943)) in not developing a hump on forehead, and in fewer dorsal spines 16 vs. 19–22 ( Roberts & Stewart 1976).

The new species shares all typical Tilapia (Coptodon) characters, which are: lower pharyngeal jaw (united 5th ceratobranchials) as long as broad with anterior keel shorter than or just as long as toothed area of jaw; posterior pharyngeal teeth more or less clearly tricuspid, but sometimes quadricuspid or pentacuspid, median pharyngeal teeth never broadened with crest-like cusps; first outer gill arch bearing 10–17 rakers; two unconnected lateral lines; only cycloid scales present; 22–30 scales in the longitudinal scale row; upper and lower outer teeth rows bicuspid in both jaws, inner rows with smaller tricuspid teeth in both jaws; isognathous or retrognathous jaws; stout teeth; caudal fin not densely scaled (except for T. nyongana , which possesses only in adults a rather densely scaled caudal fin); 13–17 dorsal spines; vertical bars (not visible in all specimens, due to conditions of preservation and/or condition of specimens before preservation), never oblique and mostly branched; pointed pelvic fin; no hump on forehead; no visor like hanging pad in pharynx (as in chromidotilapiines); only one supraneural associated with first neural spine ( Takahashi 2003; Thys van den Audenaerde 1969; Stiassny 1991; pers. observ.).

Description. Morphometric and meristic data for holotype and paratype specimens presented in Table 3 . See Figures 3a –c for general appearance. The new species appears to be a dwarf species with a maximum observed size of 85.1 mm SL. Body extremely elongated and laterally compressed. Dorsal head profile slightly convex from insertion of first dorsal spine to tip of upper lip. Head length about one-third SL, snout outline obtuse. Eye moderately large and interorbital width always larger than eye length. Greatest body depth at level of first dorsal spine. Dorsal profile, towards caudal, slightly posteroventrally curved (not straight). Caudal peduncle always longer than deep. Two unconnected lateral lines.

Squamation. All scales cycloid. Upper lateral line extending from posterior margin of gill cover to approximately center of dorsal fin. One complete row of large and one row of smaller, dorso-ventrally compressed scales separating upper lateral line from the last dorsal spine. Lower lateral line originating at level of first branched dorsal-fin rays, terminating midlaterally on caudal peduncle. One scale row between upper and lower lateral line. Preoperculum scaled with three to four regular rows; no scales on dark opercular spot. Chest scales smaller, slightly embedded scales. Base of caudal fin with minute scales.

Gill rakers. First lower gill-arch (ceratobranchial) with seven–nine gill rakers and first upper gill-arch (epibranchial) with four gill rakers with a single gill raker on cartilaginous plug included in the latter number. Total number of gill rakers on first gill-arch 11–13. Ceratobranchial rakers slender, broader on base, pointed. Gill rakers situated most ventrally on ceratobranchial gill-arch smaller than all other gill rakers.

Fins. Base of pelvic fin slightly more anterior than base of dorsal fin. Dorsal-fin base 61.4–62.3% SL, with 16 spines and 11 rays. First dorsal-fin spine always shortest, last spine always longest; longest spine always shorter than longest ray. Last dorsal-fin ray most deeply branched. Caudal-fin outline truncate or slightly emarginate. Anal-fin base 15.7–17.4% SL. Anal fin with three spines and eight rays. Third anal-fin spine always longest. Last anal-fin ray most deeply branched. Tip of longest anal-fin ray always crossing hypuralia. Pelvic-fin length 22.7– 30.7% SL. Tip of longest pelvic-fin ray not crossing anus. Pectoral-fin length 22.2–24.0% SL. Pectoral-fin rays 13. Dorsal and anal fin elongated and pointed, pectoral fin rounded.

Jaws and dentition. Jaws slightly retrognathous. Upper and lower outer teeth rows in both jaws bicuspid. Neck of anterior jaw teeth stout, crown brownish, expanded and cusps truncated with a wide cusp gap ( Fig. 4 ). Two to three incomplete inner rows of smaller tricuspid teeth in both jaws. Lower pharyngeal jaw as long as broad or somewhat broader, anterior keel shorter than toothed area ( Fig. 5 ). Most posterior pharyngeal teeth tricuspid (few bicuspid), stout, slightly hooked and regularly arranged, especially at the last two–three rows of toothed area ( Fig. 6 ). These posterior bicuspid teeth are derived from a tricuspid type, and are different than a well-marked bicuspid type (Thys van den Audenaerde, 1969). Dentigerous plate triangular. Most teeth in anterior two thirds of toothed area approach the “kukri” tooth shape (sensu Greenwood 1987) with three cusps.

Coloration in alcohol (adult specimen) ( Figs. 3a –c). Basic color brownish. Head and dorsal side dark brownish, ventral side light brownish to whitish. Chest and belly whitish with a few darker areas. Two lines of flank scales with light scale margins and a dark centre above a horizontal line at level of the lower later line. Lower lip light brownish to whitish and upper lip darker colored. Markings on body: Five or six dark vertical bars on dorsum and sides (first bar at level of first dorsal spine and last two on caudal peduncle) not reaching belly, a nape band, a supraorbital stripe and a lachrymal stripe. Vertical bars often not present. Dark opercular spot. Fins: Pectoral and pelvic fin transparent. Anal fin and caudal fin light brownish. Dorsal fin without a “ tilapia spot”. Life color unknown.

Distribution and ecology. Only known from the middle Konkouré River and its tributary, the Kakrima in Guinea ( Fig. 7 ). Occurs sympatrically with T. rheophila and T. louka . T. rheophila is also endemic to the Fouta Djalon whereas T. louka is widespread in Guinea, Liberia and Sierra Leone. The very slender body of T. konkourensis sp. nov. in combination with a rounded head shape and slightly retrognathous jaws is unique among Tilapia and suggests that it is a benthic-rheophilic species, as the combination of characters is shared with other rheophilic haplotilapiine cichlid genera, e.g., Steatocranus ( Roberts & Stewart 1976) . Many rapids cichlids are exceptionally elongate for members of their family, and this is evidently a modification for life in rapids. Such rapid habitats are very common in the Fouta Djalon region of Guinea.

Etymology. The species name konkourensis refers to the Konkouré River, the drainage to which the new species appears to be endemic. Used as a noun in apposition.

Status of Tilapia sp. aff. louka “Samou”. With the description of the new species a second rheophilic Tilapia species from the Fouta Djalon is recognized, but the status of apparently closely related Tilapia sp. aff. louka “Samou” still remains dubious. Unfortunately this species is only represented by a single adult museum specimen (MNHN 1960–0488). According to our preliminary data ( Table 3 ), Tilapia sp. aff. louka “Samou”, differs from the new species and from T. rheophila in several morphological, meristic and color characters, i.e., in a shorter anal spine length, a deeper caudal peduncle depth, a shorter distance from anus to base of anal-fin, posterior teeth of lower pharyngeal jaw are uniform tricuspid, higher number of dorsal rays, and a well marked “ tilapia spot” in the soft part of dorsal-fin. Differences to T. louka are a shorter head length, a shorter pectoral fin length, a shallower body, a lower preanal length, fewer gill rakers on ceratobranchial as well as on epibranchial, a more rounded snout, and the presence of a dark spot in the centre of each scale on the flanks above a horizontal line at level of the lower lateral-line. The body is more elongate as in T. louka . Due to the lack of additional specimens, the final status of Tilapia sp. aff. louka “Samou” remains unresolved.

Figures

FIGURE 4. Outer shape of lower jaw teeth. A = T. louka (MRAC 92 - 59 - P- 3337 - 403), B = T. konkourensis sp. nov. (MRAC 81 - 20 - P- 51) and C = T. rheophila (MRAC 81 - 20 - P- 53 - 54).

FIGURE 5. Outer shape of lower pharyngeal bone of the holotype of T. konkourensis sp. nov. (MRAC 81 - 20 - P- 51).

FIGURE 6. Outer shape and number of cusps of posterior pharyngeal teeth of lower pharyngeal jaw of A = T. louka (MRAC 92 - 59 - P- 3337 - 403), B = T. konkourensis sp. nov. (MRAC 81 - 20 - P- 52), C and D = T. rheophila (MRAC 81 - 20 - P- 53 - 54).

FIGURE 7. Map of western region of Guinea. Large black stars marking the two type locations of T. konkourensis sp. nov.; large open black star is type location as well as location of T. rheophila; small stars are locations of T. rheophila, filled star is type location of T. rheophila; filled polygon marks the location of T. sp. aff. louka “ Samou ”. Map based on a free download from http: // www. dmaps. com / carte. php? lib = guinea _ Lankarte & num _ car = 3419 & lang = de.

FIGURE 3. A. Preserved holotype of Tilapia konkourensis sp. nov. (MRAC 81 - 20 - P- 51), 85.1 mm SL; Guinea: route Korela- Kondoya, River Konkouré. B. Drawing (by R. Kühbandner) of holotype of Tilapia konkourensis sp. nov. (MRAC 81 - 20 - P- 51), 85.1 mm SL; Guinea: route Korela-Kondoya, River Konkouré. C. Preserved paratype of Tilapia konkourensis sp. nov. (MRAC 81 - 20 - P- 52), 68.7 mm SL; Guinea: route Korela-Kondoya, River Konkouré.

Tables

TABLE 3. Measurements and counts for holotype, two paratypes of T. konkourensis sp. nov. and T. sp. aff. louka “ Samou ” (MNHN 1960 - 488).

Measurements Total length (mm) Standard length SL (mm) % SL	holotype holotype + paratypes min max 111.0 88.8 111 85.1 68.7 85.1	SD	n 3 3	MNHN 1960–0488 96.3 76.6
Head length	28.8 28.8 30.4	0.8	3	29.9
Interorbital width Preorbital width Horizontal eye length Snout length	8.5 8.2 8.9 11.5 10.6 11.5 7.6 7.5 7.6 12.5 11.7 12.5	0.4 0.5 0.1 0.4	3 3 3 3	11.0 12.1 8.4 13.6
Internostril distance Cheek depth	6.7 6.7 7.0 10.8 10.6 10.8	0.2 0.1	3 3	7.4 11.1
Upper lip length Lower lip length Lower lip width Lower jaw length Predorsal distance Dorsal-fin base length	7.8 7.8 8.4 7.9 7.9 8.6 11.2 9.5 11.2 10.0 9.7 10.6 31.1 31.1 33.6 61.6 61.4 62.3	0.3 0.4 0.9 0.5 1.3 0.5	3 3 3 3 3 3	8.6 9.0 11.0 10.4 37.5 56.4
Last dorsal-fin spine length Anal-fin base length Third anal-fin spine length Pelvic-fin length	15.5 13.8 15.5 17.4 15.7 17.4 11.8 11.8 13.5 30.7 22.7 30.7	0.9 0.9 0.9 4.0	3 3 3 3	14.2 17.6 11.4 30.3
Pectoral-fin length Caudal peduncle depth	23.9 22.2 24.0 14.1 13.8 14.6	1.0 0.4	3 3	25.7 16.1
Caudal peduncle length Body depth (pelvic-fin base) Preanal length Anus-anal-fin base distance	14.5 14.5 15.3 30.0 30.0 31.3 71.4 70.0 72.9 6.8 6.2 6.8	0.5 0.8 1.5 0.3	3 3 3 3	13.6 35.9 68.7 4.3
Counts Dorsal-fin spines Dorsal-fin rays Anal-fin rays Pectoral-fin rays Scales (horizontal line) Upper lateral line scales Lower lateral line scales Gill rakers (lower) Gill rakers (upper)	16 16 (3) 11 11 (3) 8 8 (3) 13 13 (3) 25 24 (1); 25 (2) 21 21 (3) 8 8 (3) 7 7 (1); 8 (1); 9 (1) 4 4 (3)		3 3 3 3 3 3 3 3 3	15 13 9 14 25 20 11 8 3