Dwarf Moon Tetra

description

Description. Based on holotype and 15 paratypes. For general appearance refer to Figs. 1 and 2. Measurements and meristics summarized in Tables 1 and 2. A comparatively small species, maximum size 24.4 mm SL. Body laterally compressed, slightly elevated. Dorsal fin originating midway along body; pelvic fins originating slightly in front of dorsal fin; anal fin originating approximately at level of end of dorsal-fin base; adipose fin originating at level of caudal end of anal-fin base, positioned closer to caudal than to dorsal fin. Scale cover variably reduced: no pre-dorsal scales; usually no scales on caudal peduncle; usually a scale free patch on middle of flank at level of pelvic-fin origin. Number of pored scales in lateral line variable (0 – 9); lateral line never complete. Premaxilla with two teeth in outer row, each with three major and two minor cusps and four teeth in inner row with four cusps in the first, six cusps in the second and third, and seven cusps in the last tooth (Fig. 3). Dentary with four teeth in outer row, each with six cusps, except the last with only five cusps (Fig. 3); an inner single monocuspid tooth usually absent (where it was possible to check this

Description of two new Bathyaethiops species (Teleostei: Alestidae) from the Congo basin

diagnosis

Differential diagnosis. Distinguished from all congeners by an incomplete squamation with the scale cover variably reduced to no pre-dorsal scales, usually no scales on caudal peduncle, and usually a scale-free patch on middle flank at about level of pelvic-fin origin. Furthermore distinguished by a unique color pattern, i. e., a combination of a humeral spot of about pupil-size and the absence of dark vertical bars along midlateral flanks. Difficult to distinguish from juvenile B. caudomaculatus, from which the new species differs by the (usually) absence of unicuspid teeth in the second row of lower jaws (vs. presence), and (usually) the absent or rudimentary supraneural between two neural spines directly in front of the first dorsal fin pterygiophore (vs. well developed).

Description of two new Bathyaethiops species (Teleostei: Alestidae) from the Congo basin

distribution

Distribution and habitat. The species is so far known from several localities along the Ngoko River, from below the Nki falls to the village of Ndongo (Fig. 4 – 5). The Ngoko, called Dja River above the Nki falls, is a tributary to the Sangha River, a major northern tributary of the Congo River. All specimens were caught in the main river channel, usually in or close to riparian vegetation over a substrate of fine particles and organic material. Water parameters from the Ngoko River at Ndongo taken on 0 4.02.2008 were: pH 7.08; conductivity 23 µS; temperature 27.5 ° C. Meristic character Holotype Paratypes (N = 15) Simple dorsal fin rays 3 2 (15) Branched dorsal fin rays 8 8 (15) Simple anal fin rays 3 3 (15) Branched anal fin rays 21 18 (1); 19 (5); 20 (7); 21 (1); - (1) Upper procurrent caudal fin rays 9 5 (1); 6 (5); 7 (5); 8 (4) Upper principal caudal fin rays 10 10 (13); 11 (2) Lower principal caudal fin rays 9 9 (14); 10 (1) Lower procurrent caudal fin rays 7 5 (4); 6 (10); 7 (1) Vertebrae 37 35 (1); 36 (11); 37 (3) Abdominal vertebrae 16 16 (4); 17 (10); 18 (1) Caudal vertebrae 21 19 (10); 20 (5) Dorsal fin inserting after vertebra 10 10 (10); 11 (5) Anal fin inserting after

Description of two new Bathyaethiops species (Teleostei: Alestidae) from the Congo basin

etymology

Etymology. Named after the Baka people, the native hunter-gatherer tribe in Southeastern Cameroon, where the species was found. A noun in aposition.

Description of two new Bathyaethiops species (Teleostei: Alestidae) from the Congo basin