Nothobranchius balamaensis Bragança & Chakona, 2022

Family:  Nothobranchiidae (African rivulines)
Max. size:  2.98 cm SL (male/unsexed)
Environment:  pelagic; freshwater
Distribution:  Africa: seasonal Naconha River, upper Montepuez River system, in north-eastern Mozambique (Ref. 127332).
Diagnosis:  Dorsal spines (total): 0-0; Dorsal soft rays (total): 16-17; Anal spines: 0-0; Anal soft rays: 17-18. Diagnosis: Nothobranchius balamaensis is distinguished from all other members of the genus, except N. kirki, by the following unique combination of characters in males; body colouration bright iridescent light blue, with narrow brown-red to orange scale margins creating an irregular reticulated pattern; anal and caudal fins overall orange, darker in basal and proximal zones, grading through medial zone to lighter orange in distal zone and devoid of distinctive markings or banding; dorsal fin with marbled pattern in proximal region comprising irregular brown-red markings on yellow-orange background, distinct striated pattern parallel to fin rays in medial and distal zones with inter-ray membrane distinctive black between first 4-5 rays; anal fin shape mildly trapezoidal (Ref. 127332). Nothobranchius balamaensis differs from the closely related and most similar N. kirki by some elements of male colour pattern: anal fin devoid of markings or banding in proximal zone, vs. narrow light blue to white proximal band or series of irregular markings in N. kirki; dorsal fin with marbled proximal zone and prominently striated medial and distal zones, vs. marbled or vermicular pattern throughout proximal and medial zones with only a hint of striation pattern in distal zone of some specimens (Ref. 127332).

Description: Dorsal profile concave to nearly straight on head, convex from nape to end of dorsal-fin base; slightly concave to nearly straight on caudal peduncle; ventral profile convex from lower jaw to end of anal-fin base insertion; slightly concave to nearly straight on caudal peduncle; body moderately elongate and slender; greatest body depth at vertical at pelvic-fin origin (Ref. 127332). Head triangular in lateral view; snout slightly pointed; mouth directed upwards, lower jaw slightly projecting past anterior limit of upper jaw; jaw teeth canine, irregularly arranged, outer teeth greater in number than inner teeth (Ref. 127332). Dorsal fin in male sub-rectangular, extremity rounded, with very short rudimentary fin-ray extensions along distal margin, tip reaching posterior portion of caudal peduncle; anal fin mildly trapezoidal with rounded extremity, short filaments along distal margin, tip reaching middle portion of caudal peduncle; in female, dorsal fin rounded, anal fin typically sub-triangular, slightly longer than dorsal fin, tip reaching middle portion of caudal peduncle; caudal fin subtruncate, posterior margin slightly convex; pectoral fin sub-elliptical, posterior extremity reaching pelvic-fin base; pelvic fin small, tip reaching between anus and anal-fin origin in male, reaching anus in female; pelvic-fin bases in close proximity; dorsal-fin origin on vertical slightly in front of anal-fin origin; dorsal and anal fin bases covered with opaque mucous film and with papillate contact organs along fin rays, denser on anal fin (Ref. 127332). Scales cycloid, body and head entirely scales, except ventral surface of head; body squamation extending over 25% of caudal fin; no scales on dorsal and anal fin bases; cephalic squamation pattern irregular G-type; scales in mid-longitudinal series 27-28, transverse scales 9, circumpeduncular scales 12 (Ref. 127332). Two neuromasts anteriorly positioned, placed in shallow depressions, just before rostrum; anterior supraorbital series of neuromasts arranged in two separate sections, each placed in shallow depression, anterior section with one or two neuromasts, posterior section with two; additional minute neuromast may be present between depressions; posterior supraorbital series with three to four neuromasts in shallow depression; infraorbital series with 2-3 neuromasts in preorbital region followed by 12-15 minute neuromasts, and by one well-developed neuromast in posterior region; pre-opercular series in open groove with 14-19 neuromasts; mandibular 16-17; one neuromast per scale of lateral line (Ref. 127332).

Colouration: Colouration in alcohol of male: flank, dorsum and head light brown; body overall yellow-brown, lighter ventrally; dorsal fin pale grey with chromatophores scattered over entire fin, concentrated close to insertion of fin rays; membrane between anterior rays black; anal fin pale grey in proximal portion, hyaline in medial and distal portions; caudal fin pale grey; pectoral and pelvic fins hyaline, with minute chromatophores scattered over fin membrane (Ref. 127332). Colouration in alcohol of female: flank and dorsum pale brown, side of head and ventral region pale yellow, darker in dorso-anterior region, chromatophores forming distinct reticulation pattern; all fins hyaline, with small chromatophores scattered over fin membrane (Ref. 127332). Live colouration of male: scales on flank and head iridescent light blue to turquoise with dark brown-red margins, grading to orange posteriorly and ventrally, creating a reticulation pattern; scales on the abdomen smaller, pale iridescent light blue with prominent orange margins; scales on dorsum grade to blue-grey with darker grey margins; lips, snout, frontal and dorsal portion of head light grey-brown; ventral portion of head light blue to white; dorsal fin with marbled pattern in proximal region, comprising blue to yellow-orange background with irregular brown-red marbled markings; medial and distal zones show distinct striated pattern parallel to fin rays which grade from light blue anteriorly through pale orange in the middle part of fin to darker orange posteriorly; inter-ray membrane distinctive black between the first 4-5 anterior rays, grading to dark brown-red and dark orange posteriorly; very short fin-ray extensions appear grey; anal fin orange, darker in proximal zone, becoming lighter in medial and distal zones which show indistinct striation pattern parallel to the fin rays, in relatively darker and lighter shades of orange; short fin-ray extensions grey; caudal fin deep orange in basal, proximal and medial zones grading to lighter orange in distal zone with striation pattern parallel to fin rays in relatively light and dark orange; narrow marginal zone grey; pelvic fin orange; pectoral fin hyaline; iris yellow to blue, with indistinct black vertical bar through centre of eye (Ref. 127332).

Biology:  Found in pool in a seasonal stream course, less than 1 m in depth, with turbid and slow flowing water; riverbanks were covered by grass with remnants of Miombo vegetation (Ref. 127332).
IUCN Red List Status: Endangered (EN); Date assessed: 16 August 2022 (B1ab(iii)) Ref. (130435)
Threat to humans:  harmless
Country info:   
 


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