Nothobranchius balamaensis Bragança & Chakona, 2022

Bragança, Pedro H. N., Bellstedt, Dirk U., Merwe, P. De Wet Van Der, Cotterill, Fenton P. D., Watters, Brian R. & Chakona, Albert, 2022, Nothobranchius balamaensis (Cyprinodontiformes: Nothobranchiidae), a new species of annual killifish from northern Mozambique, Zootaxa 5174 (5), pp. 508-524 : 511-516

Nothobranchius balamaensis Bragança & Chakona , new species

Figures 2 , 3 , 4 ; Table 1

Nothobranchius sp. “Northern Mozambique ” Van der Merwe et al. (2021).

Holotype. SAIAB 190261 , male, 29.8 mm SL; Muhukwa upstream bridge on second tributary south-east of Balama village, Cabo Delgado Province, Mozambique, 13°25’59.1’’S 38°36’41.2’’E; Chakona, A; 05 Mar 2013.

Paratypes. SAIAB 190255 , 2 males (27.5–28.9 mm SL), 1 female (29.0 mm SL); site and collection data as for holotype .

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 brownred 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. 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).

Description. General body features illustrated in Figures 2 and 3 , morphometric and meristic characters of holotype and paratypes presented in Table 1 . The specimens examined were sexually mature but had probably not reached maximum adult size, although this may be one of the smaller members of the genus, with standard length of 29.8 mm in the largest of the three available males. 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. 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.

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 (mean for males: predorsal length as % of SL 61.4; preanal length 62.6). Dorsal and anal fin bases covered with opaque mucous film and with papillate contact organs along fin rays, denser on anal fin.

Scales cycloid, body and head entirely scaled, except ventral surface of head ( Fig. 4 ). Body squamation extending over 25% of caudal fin; no scales on dorsal and anal fin bases. Cephalic squamation pattern irregular G-type.

Two neuromasts anteriorly positioned, placed in shallow depressions, just before rostrum ( Fig. 4 ). 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.

Colouration in alcohol. Male ( Fig. 2A ). 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.

Female ( Fig. 2B ). Flank and dorsum pale brown, side of head and ventral region pale yellow, darker in dorsoanterior region, chromatophores forming distinct reticulation pattern. All fins hyaline, with small chromatophores scattered over fin membrane.

Live Colouration. Male ( Fig. 3 ). Scales on flank and head iridescent light blue to turquoise with dark brownred 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.

Distribution. Nothobranchius balamaensis is known only from the type locality, in the seasonal Naconha River, a sub-catchment of the upper Montepuez River system in the Balama region of the Cabo Delgado Province, north-eastern Mozambique ( Fig. 5 ).

Ecology. The habitat comprised a pool in a seasonal stream course (<1 m in depth) with turbid and slow flowing water ( Fig. 6 ). The substratum was predominantly fine mud interspersed with sections of fine sand. The riverbanks were covered by grass with remnants of Miombo vegetation. Nothobranchius balamaensis occurred syntopically with N. makondorum , and the cyprinid Enteromius litamba .

The documented rainfall pattern affecting north-eastern Mozambique indicates an extended dry season in autumn, winter and spring (May to November) with a single distinct rainfall season from December to April. Total annual rainfall as for example at Mocimboa da Praia (969 mm), Pemba (874 mm) and Nampula (1059 mm) is typical for the region (after WorldClimate website 2016) and a similar rainfall pattern may be expected in the Balama area where Nothobranchius balamaensis occurs.

This unimodal rainfall pattern differs from the bimodal pattern seen further north in the central coastal part of Tanzania. Coastal areas to the north as close as Kilwa in Tanzania (approximately 290 km from Balama) show what could be referred to as a moderately bimodal rainfall pattern with peaks in November-December (short rains or “vuli”) and March-May (long, more intense rains or “masika”) separated by an interval of lesser rainfall.

Etymology. The specific name, balamaensis , refers to the Balama region in the Cabo Delgado Province, Mozambique, where the type locality for the species is located.

Figures

FIGURE 2. Nothobranchius balamaensis, preserved specimens: A, male, holotype, 29.8 mm SL (SAIAB 190261); B, female, paratype, 29.0 mm SL (SAIAB 190255).

FIGURE 3. Nothobranchius balamaensis, male, holotype, 29.8 SL (SAIAB 190261) showing live colouration.

FIGURE 4. Diagrammatic representation of the latero-sensory system and frontal squamation on the dorsal surface of the head in Nothobranchius balamaensis. Abbreviations: asss: anterior section of the anterior supraorbital series; an, anterior naris; pn, posterior naris; psss: posterior section of the anterior supraorbital series; poss: posterior supraorbital series; prn: posterior rostral neuromast.

FIGURE 5. Type localities of Nothobranchius species occurring in northern Mozambique and neighbouring regions. Red elipse, N. balamaensis; yellow lozenge, N. kirki; orange four pointed star, N. wattersi; light blue dot, N. niassa; green square, N. makondorum; purple arrow, N. hengstleri; blue five pointed star, N. krammeri.

FIGURE 6. Type locality of N. balamaensis, a seasonal pool in the Montepuez River system, Balama region, Cabo Delgado Province, northern Mozambique. Photographed on 5 March, 2013.