Pseudocrenilabrus pyrrhocaudalis Katongo, Seehausen & Snoeks, 2017, sp. nov.

Pseudocrenilabrus pyrrhocaudalis sp. nov.

Fire-tailed Pseudocrenilabrus

Figs. 1, 2. Tables 2, 3.

Holotype. SAIAB-191528, male 62.8 mm SL; Zambia; Kalobwa Beach (1,134 meters above sea level with coordinates 8°57'0" S and 29°6'0" E), Lake Mweru, Luapula-Congo River system, seine net, C. Katongo and O. Seehausen, 15 September 2005 (Fig. 1 a).

Paratypes. MRAC A9-034-P-0238-247, 57.3–73.1 mm SL, Luapula-Congo River system, Mukwakwa, Lake Mweru, Zambia, P. van Zwieten, 1994; MRAC A4-025-P0103-07 and MRAC A4-025-0137-38, 46.5–54 mm SL, Luapula-Congo River system, Mwatishi River / Lake Mweru confluence, gillnet, C. Katongo, 2002; SAIAB 191530 (1-13), 45.3–68.3 mm SL, Luapula-Congo River system, Kalobwa beach, Lake Mweru, C. Katongo and O. Seehausen, September, 2005.

Diagnosis. Pseudocrenilabrus pyrrhocaudalis can be differentiated from the other species of the genus Pseudocrenilabrus on the basis of its colour pattern and its subtruncate caudal fin. Male P. pyrrhocaudalis have a unique colour pattern characterized by some orange colour on their anal and caudal fins that can become bright orange-red in breeding males, extending over the proximal parts of the anal and caudal fins and the distal part of the caudal and the upper and lower parts of the caudal peduncle (Fig. 1 a). In addition, P. pyrrhocaudalis can be distinguished from its sympatric congener P. philander (Fig. 3), by a combination of the following characters (Figs.1, 2, 4; Tables 2, 3): pelvic fin white (vs. black), posterior part of dorsal fin orange (vs. olive green in the other species), comparatively thinner lips (vs. comparatively thicker lips), larger eye diameter 27.0–39.3% HL (vs 22.9–33.1% HL), narrower head width 37.0–47.3% HL (vs. 38.5–53.7% HL), narrower interorbital distance 14.6– 22.3% HL (vs. 20.5–29.4% HL) and a more slender caudal peduncle 8.8–11.8% SL (vs. 11.3–13.9% SL), and 50.0–64.7% CPL (vs 64.3–93.5% CPL).

Description. In both sexes: body relatively deep, head profile somewhat convex, mouth inclined upwards with relatively thin lips, interorbital distance narrow, caudal fin sub-truncate. Lower pharyngeal bone relatively slender and slightly longer than wide. Pharyngeal teeth all fine; those of the posterior row clearly larger than the others. Teeth of the two median rows somewhat enlarged. There is a small gradient in the orientation of the major cusp of the pharyngeal teeth from slightly backwards on the anterior parts of the pharyngeal jaw towards more erect posteriorly and slightly forward in the posteriormost rows. Breeding males with a bright orange coloration on caudal and anal fins; an orange spot on the anal fin, distal parts of caudal and anal fins white. Base of the caudal fin bright orange more than 2/3 of fin. Head and upper lateral part of body grey, while the lower part yellowish orange. Dorsal fin with white lateral dots arranged as stripes radiating from base to tips of dorsal-fin rays. Pelvic fins bright white (Fig. 1 a). Females generally grey, with no anal-fin spot; pelvic fins bright white; bright orange lower half of caudal; some orange flashes at base of caudal and anal fins; some spots and streaks on dorsal and caudal fins (Fig. 2 a).

A scatter plot of mainly male specimens of P. pyrrhocaudalis sp. nov. and Lake Mweru P. philander on the first and second axes of a PCA on log transformed measurements (Figure 4) shows that there are clear morphological differences between the two species. The characters with the highest loadings on the second axis (responsible for the observed morphological differences) are caudal peduncle length (CPL), interorbital width (IOW), eye diameter (ED), anal fin base (AFB), head width (HW) and caudal peduncle depth (CPD), (Table 1). Comparisons of morphometric ratios between P. pyrrhocaudalis sp. nov. and P. philander (Table 2) indicate that the characters responsible for the observed morphological differences are eye diameter as a proportion of head length (ED_HL), interorbital width as a proportion of head length (IOW_HL) and as a proportion of head width (IOW_HW), head width as a proportion of head length (HW_HL), caudal peduncle depth as a proportion of standard length (CPD_ SL) and as a proportion of caudal peduncle length (CPD_ CPL). Comparisons of meristic counts between P. pyrrhocaudalis sp. nov. and P. philander (Table 3) indicate that the characters responsible for the differences are number of upper jaw teeth (UJT), number of upper jaw inner rows (UJIR), dorsal spiny rays (Dspiny), anal soft rays (Asoft) and number of scales around the caudal peduncle (CP). The columns with Mann Whitney U test results (probabilities) in both Tables 2 and 3 were generated using P. pyrrhocaudalis sp. nov. and P. philander specimens of similar size class (44–73mm SL). These results (in the last column of each of Tables 2 and 3) indicate the relative contribution of the highlighted characters to the differences between the two species.

Etymology. Named Pseudocrenilabrus pyrrhocaudalis because this species has a bright orange tail which resembles a flame of fire. The common name fire-tailed Pseudocrenilabrus is proposed for this species. Distribution. Probably endemic to Lake Mweru where it has been found near the beaches at Kalobwa, Kabuta, Ntoto and Kashikishi and at the Mwatishi River estuary (Fig. 5).

Variable PC1 PC2 PC3

Lachrymal depth 0.851 0.142 -0.207

Snout length 0.893 0.241 -0.044

Lower jaw length 0.872 -0.250 0.249

Premaxillary pedicel length 0.958 0.025 0.056

Cheek depth 0.934 -0.034 0.061

Eye diameter 0.613 -0.465 -0.596

Interorbital width 0.810 0.485 0.043

Head width 0.905 0.310 -0.007

Head length 0.983 0.023 -0.030

Standard length 0.978 -0.124 0.062

Body depth 0.952 0.006 0.106

Dorsal fin base length 0.964 -0.081 0.118

Anal fin base length 0.824 -0.316 0.323

Predorsal distance 0.972 0.040 -0.064

Prepelvic distance 0.933 0.024 0.012

Preventral distance 0.976 -0.023 -0.064

Pre-anal distance 0.972 0.044 -0.057

Caudal peduncle length 0.685 -0.579 0.041

Caudal peduncle depth 0.888 0.280 -0.166

Explained variance 15.333 1.231 0.646

Proportion of total variance 0.807 0.065 0.034