Chromidotilapia nana, Anton Lamboj, 2003

Anton Lamboj, 2003, Chromidotilapia melaniae and C. nana, two new cichlid species (Perciformes, Cichlidae) from Gabon, Central Africa., Zootaxa 143, pp. 1-15 : 7-10

Chromidotilapia nana , new species

(Figs. 5-7)

Holotype. MRAC-A2-011-P-1, female, 56.7 mm SL; Gabon: Riv. Mougalaba near the village of Pendudu on the route Tchibanga-Ndende, Nyanga system, A. Lamboj, D. Altmann, M. Hasselmann & F. Panholzer, Aug 2000.

Paratypes. All with same data as holotype: MRAC-A2-011-P-2-6, 2 males, 3 females, 46.5-58.9 mm SL. - AMNH 232532, 2 males (one cleared and stained), 4 undet., 26.8- 57.9 mm SL. - NMW 94633, 3 males, 1 undet., 37.4-54.3 mm SL.

Additional material. Eight pairs from the type locality were collected for behavioural observations, but not included in the type series.

Diagnosis. Chromidotilapia nana differs from congeners in having only a single row of teeth in upper and lower jaws. It also attains a smaller adult size than congeners (less than 60 mm SL).

Description. Measurements and meristic counts for holotype and 15 paratypes are given in Table 2.

Smallest adult size of the genus (not exceeding 58.9 mm SL vs. 76.7-127.8 mm in congeners). Sexual dimorphism and dichromatism poorly developed. First ray of pelvic fin longest in both sexes, but always slightly more produced in males than in females. Pelvic fin reaching or overlapping spinous anal fin in both sexes when adducted. Caudal fin rounded.

Osteology and dentition. Infraorbital series complete with lachrymal and four additional bones; lachrymal with five openings of laterosensory system. Neurocranial apophysis of Tilapia type. Vertebral count 24-25 vertebrae, 11-12 abdominal and 12-13 caudal.

Premaxilla with a single row of unicuspid teeth. Dentary usually with a single row of unicuspid teeth (three adult specimens with 1 - 5 teeth forming a truncated second row in dentary). Anteriorly in lower jaw, some teeth orientated posteriorly, not buccally. Lower pharyngeal bone triangular, with shouldered unicuspid teeth in lateral fields and asymmetric bicuspid teeth in central field.

Gill rakers on first arch. Nine-10 tuberculate gill rakers on hypobranchial + ceratobranchial, 6-8 pointed gill rakers on epibranchial. Well developed visor-like hanging pad on roof of the pharynx.

Squamation. Cycloid, 3 rows of scales on cheek, 3-4 horizontal rows on opercle. Naked dark spot on outer edge of opercle always unscaled. Chest-scales smaller than body scales.

Upper lateral line separated from dorsal-fin base on highest point (8th pored scale) by 2 scales, on last pored scale by 1-1½ scales. End of upper lateral line sometimes overlapping lower lateral line by one scale row.

About ¼ - ½ of caudal fin basally covered with scales; other fins unscaled.

Coloration. Living specimens of both sexes (Figs.6-7): Head and body light brown with a rosy overlay. Dark scaleless spot on the outer edge of opercle. Two rows of dark spots and blotches sometimes visible on flanks. One row of 4-5 small spots, first more or less at the highest point of upper lateral line and remainder directly under the dorsal fin base. Second row with two larger ovoid blotches at mid body and another large rounded blotch on caudal peduncle, additional smaller spots in middle row between larger spots sometimes visible. Lips, cheeks and parts of opercle often iridescent yellow. Ventral parts of head with iridescent and silvery parts, some scales on body and caudal peduncle with silvery coloration.

Male coloration: Dorsal fin with red to orange margin, followed by a thin, rosy and iridescent band. Other parts of this fin hyaline anteriorly to red posteriorly. Caudal fin rosy to red medially, yellow dorsally and ventrally. Anal rosy to red, with violet base and dark coloured outer margin. Leading edge of pelvic fins dark blue to dark violet, remainder of fin rosy to violet. Pelvic fins hyaline to slightly yellow. Body scales with dark margins.

Female coloration: Dorsal fin iridescent white to rosy, hyaline to yellow distally. Dorsal margin of caudal fin iridescent white to rosy, remainder of fin hyaline medially to yellow distally. Anal fin and pelvic fins rosy to violet, with yellowish posterior and dark coloured anterior edge. Pectoral fins yellow.

Preserved specimens (Fig.5): Coloration of head and body brown, spots and blotches as in living specimens, but always darker brown to black.

Breeding behaviour. No data from populations in the wild are available. Observations in aquaria indicate this species is a monogamous, pair bonding biparental ovophilic mouthbrooder. Eggs are deposited on a hard layer (rocks, wood) or leaves. After the entire clutch is deposited, eggs are incubated by the female for the first 2 or 3 days, after this periodical changes of incubation between female and male are possible, but normally the female is more dominantly involved. Total hatching of eggs and larvae is for 12-14 days in the buccal cavity of the parents.

Comparisons. Chromidotilapia nana differs from all congeners in having a single row of teeth in the lower jaws in adults (vs. 2-3 rows in all other species), and in attaining a smaller adult size (largest specimen 58.9 mm SL versus 76.7-127.8 mm SL in congeners). It differs from C. schoutedeni in having 5 (versus 4) pores on the lachrymal, and from C. guntheri and C. regani in having a low number of gill rakers o the lower limb of the first arch (9-10 vs. 11-16). It also has a distinctive coloration, differing from all congeners with the exception of C. mrac in having two rows of dark blotches sometimes visible on the body (vs. stripes or interrupted stripes). It is also relatively distinctive in lacking spots, tips or other similar marks on the dorsal, caudal and anal fins of males. It differs from C. mrac and C. kingsleyae in breeding behaviour (pair bounding, biparental ovophilic mouthbrooder in C. nana vs. pair bounding, female larvophilic mouthbrooder in C. mrac or polygamous ovophilic mouthbrooder in C. kingsleyae ).

Distribution. Gabon, only known from the type locality (Fig.8).

Etymology. Refers to the relatively small adult size of the species when compared with congeners.