Nothobranchius janpapi Wildekamp, 1977

Watters, Brian R. & Nagy, Béla, 2025, A review and redefinition of the subgenus Aphyobranchius Wildekamp, 1977, in the seasonal killifish genus Nothobranchius Peters, 1868 (Teleostei: Nothobranchiidae), from ephemeral wetlands of eastern Tanzania, Zootaxa 5570 (3), pp. 401-446 : 407-411

Nothobranchius janpapi Wildekamp, 1977

( Figs. 2A–D )

Material examined. RMCA 77-16 -P-19, holotype, male, 33.7 mm SL ; – RMCA 77-16 -P-20, female, 28.9 mm SL ; – RMCA 77-16 -P-21-23, 2 females, 28.2–28.6 mm SL; Tanzania: Ruvu drainage, Kwaraza, approx. 06°41.8’ S, 38°42’ E; R. Wildekamp, T. Steinfort, J. Lourens, R. van Haarlem ; 12 June 1976; field code: T 76-8 .

Additional material examined. 1 male, 27.7 mm SL; Tanzania: Ruvu drainage, Kwaraza; 06°40.818’ S, 38°39.829’ E; B. Nagy; 12 January 2009; field code: TZN 09-4 . – 1 male, 28.4 mm SL; Tanzania: Ruvu drainage, Soga; 06°50.14’ S, 38°50.80’ E; B. Watters, J. Rosenstock, M. Agnew, F. Larsen; 29 May 1998; field code: TAN 98- 14 . – 1 male, 32.6 mm SL; Tanzania: Ruvu drainage, Soga; 06°50.19’ S, 38°50.78’ E; B. Watters, R. Wildekamp, B. Cooper; 12 June 1997; field code: TAN 97-45 . – 1 male, 32.0 mm SL; Tanzania: Rufiji drainage, Kitonga; 08°03.110’ S, 39°00.510’ E; B. Watters, B. Cooper, W. Bishopp; 29 May 2003; field code: TAN 03-22. – 5 males, 22.2–25.6 mm SL , 2 females, 21.1–23.5 mm SL; Tanzania: Ruhoi drainage, Ngulakula; 07°48.073’ S, 38°48.739’ E; B. Watters, B. Cooper, O. Schmidt; 4 June 2002; field code: TAN 02-13 .

Diagnosis. Nothobranchius janpapi belongs to the N. janpapi species group within the subgenus Aphyobranchius by presenting the following combination of characters in the male: light blue body colouration with narrow red scale margins and yellow-brown to yellow-green dorsum stripe; rearward positioned dorsal fin with predorsal length of 63.3–67.9 % SL and predorsal length 109–115 as percentage of preanal length; dorsal fin relatively small with low number of rays, 12–14; cephalic sensory system at supraorbital level in an undivided, slightly curved, almost flat, shallow groove with three exposed neuromasts and pronounced lobes ( Fig. 3a ). Both sexes with central 2–3 rays of the caudal fin slightly elongated forming a mild posterior lobe (vs. central lobe absent). Nothobranchius janpapi is distinguished from the other members of the N. janpapi species group by male colouration of anal fin with slender orange-red distal band and narrow light blue margin (vs. slender yellow subdistal band with narrow red distal band); caudal fin base and proximal zone olive, with light grey to translucent subdistal band and narrow dark grey distal band (vs. base and proximal zone grey to light red with slender red subdistal band and narrow black distal band in N. luekei , and caudal fin plain red to orange-red with narrow black distal margin in N. geminus ); dorsal fin with narrow light-blue distal band (vs. slender red in N. luekei and narrow black in N. geminus ); pelvic fin orange-red with narrow light blue distal band (vs. light blue with narrow red distal margin in N. luekei , and yellow to red with narrow black margin in N. geminus ); as well as morphometric characters in males of head depth 74–81 % HL (vs. 66–72 in N. geminus and 55–63 in N. luekei ); suborbital depth 16–20 % HL (vs. 10–14 in N. geminus and 8–12 in N. luekei ); and caudal peduncle length 133–140 in % of its depth (vs. 121–130 in N. geminus and 148–156 in N. luekei ). Further, it differs from N. geminus by dorsal-fin base length 18.8–25.1 % SL vs. 15.6–18.6, and from N. luekei by predorsal length 63.3–67.9 % SL vs. 68.0–73.0, and head width 58–65 % HL vs. 52–56.

Description. General body features illustrated by Figures 2A–D . Morphometric and meristic characters of examined material are summarized in Table 3 .

Male: Small Nothobranchius species, maximum examined size 33.7 mm SL. General body shape laterally compressed. Greatest body depth at vertical in front of pelvic-fin origin (27.4–31.0 % SL). Greatest body width at pectoral-fin base with body progressively narrowing towards caudal-fin base. Dorsal profile slightly convex to straight from tip of snout to dorsal-fin origin, straight to slightly concave on caudal peduncle. Ventral profile convex from lower jaw to base of last anal-fin ray, straight to slightly concave on caudal peduncle. Caudal peduncle moderately deep, length 133–140 % of its depth. Anus situated directly in front of anal-fin origin.

Head moderately long (25.6–30.6 % SL), laterally compressed, deeper than wide (head width 74–81 % of its depth). Snout distinctly pointed, smaller than eye diameter. Mouth supraterminal, slightly oblique in profile. Jaws subequal, lower jaw longer than upper, posterior end of rictus at same level or slightly ventral to centre of eye. Premaxilla and dentary with many irregularly distributed conical teeth on inner rows and slightly curved teeth on outer row. Orbit large, eye diameter 34–38 % HL, mainly in anterior half of head (snout to eye end length 51–59 % HL). Branchiostegal membrane projecting posteriorly from opercle.

Dorsal-fin origin markedly posterior to anal-fin origin (predorsal length 109–115 as % of preanal length), both fins originating posterior to mid-length of body (predorsal length 63.3–67.9 % SL; preanal length 55.5–59.9 % SL). Dorsal fin relatively small with low number of rays,12–14; extremity rounded. Anal fin trapezoidal in shape, with 16–19 rays; lower margin mildly concave in profile. Dorsal and anal fins usually with short fin-ray extensions. Pectoral fin subtriangular, insertion slightly posterior to margin of opercular opening, base slightly oblique, upper fin rays positioned slightly anterior to lower fin rays, with tip reaching or slightly overlapping base of pelvic fin. Pelvic fin subabdominal, origin at about mid-length of body, short, base medially separated, with tip reaching urogenital papilla. Caudal fin rounded, with 13–18 branched rays, plus 2–3 dorsal and ventral procurrent rays; central 2–3 rays of fin commonly relatively slightly elongated resulting in mild central lobe.

Scales cycloid, body and head entirely scaled, except for ventral surface of head. No scales on base of dorsal and anal fins. Scales in mid-longitudinal series 26–28 plus two or three small scales on caudal-fin base. Transverse rows of scales in front of dorsal-fin origin 11; scale rows around caudal peduncle 12.

Cephalic squamation pattern G-type. Frontal neuromast in single shallow groove behind upper lip. Cephalic sensory system at supraorbital level in an undivided, slightly curved, almost flat, shallow groove with three exposed neuromasts and pronounced lobes ( Fig. 3a ), whereas at supratemporal level with three exposed neuromasts in slightly curved arrangement on flat surface, with pronounced lobes. Preorbital canal in shallow groove with 2–3 exposed neuromasts; infraorbital level with series of about 15 small buttons at ventral and posterior margin of orbit; postorbital canal in shallow groove with one exposed long neuromast. Preopercular system with six exposed neuromasts in deep groove on preopercle portion, whereas in shallow groove with four exposed neuromasts on ventral portion. Mandibular canal in shallow groove with about ten small buttons. One neuromast on each scale along trunk mid-longitudinal series.

Female: Smaller than male, maximum recorded size 28.9 mm SL. Branchiostegal membrane not projecting posteriorly from opercle. Dorsal fin rounded with low number of rays, 12–14. Caudal fin basically rounded but with central 2–3 rays slightly elongated resulting in mildly pointed posterior margin. Anal fin subtriangular, tip rounded, central rays longer and more rigid. Anal fin positioned more posteriorly than in males (preanal length 60.5–65.2 % SL vs. 55.5–59.9). Anal-fin base length smaller than in males (18.7–20.4 % SL vs. 22.8–27.1). Head depth smaller than in males (67–69 % HL vs. 74–81; suborbital depth 11–14 % HL vs. 16–20), whereas head width 85–90 in % of its depth vs. 74–81. Caudal peduncle shallower than in male (caudal peduncle depth 10.7–11.8 % SL vs. 12.7–15.0; caudal peduncle length 184–190 % of its depth vs. 133–140).

Colouration. Live male ( Figs. 2A–C ): Scales on trunk and head light iridescent blue with narrow red to less commonly grey-brown margins, forming a regular reticulation pattern. Scales on abdomen faint blue to white with less pronounced margins. Scales on the dorsum anterior to dorsal fin may have yellow-brown centres. Snout, frontal and dorsal portions of the head are yellow-brown; the throat is yellow. Operculum has light blue markings. Exposed part of branchiostegal membrane is yellow with white edging. Iris is blue to blue-green. Dorsal fin background is green to yellow-green grading to grey in the distal zone with a light blue margin that may be white in the very short fin-ray extensions; the background is overlaid by small red spots that may be denser and larger in the basal and proximal zones, becoming smaller and, in some populations, dark grey in the medial and distal zones. Anal fin background comprises a light blue basal zone grading to yellow-brown or yellow-green in the proximal and medial zones which are overlaid by prominent red stripes over fin rays; in some populations these red stripes may be partially broken into irregular spots. The development of red stripes is variable at both the inter- and intrapopulation level; in some they are narrow, allowing the yellow-brown or yellow-green background to dominate, while in others they are broad and dense resulting in an almost solid red fin and merging with the commonly present orange-red distal zone. A narrow, often only partially developed, light blue margin is usually present on the anal fin. Basal, proximal and medial zones of the caudal fin are olive grading into a light grey to translucent subdistal zone that, in turn, grades into a darker grey outer component. Faint red spots may be present on the basal, proximal and submedial zones and may be arranged concentrically conforming to the general outer shape of the fin; less commonly, there may be radiating red stripes parallel to fin rays. Many populations also show orange-red markings along the lower, and more rarely upper, marginal parts of the distal zone of the caudal fin, extending from the fin base and decreasing anteriorly. Pelvic fins are orange-red with poorly developed blue-white edges. Pectoral fins are dominantly hyaline with poorly developed, and usually only partial, blue margins.

Live female ( Fig. 2D ): Trunk and head light grey, darker on the dorsum and lighter ventrally. Scales on the flanks have narrow darker grey-brown margins; scale centres on the trunk above the abdomen are iridescent pale blue; the operculum is iridescent light blue. All fins hyaline. The iris is light golden.

Distribution. Nothobranchius janpapi is endemic to seasonal freshwater habitats in coastal Tanzania and is the most common, but second most widespread, member of the Aphyobranchius subgenus, occurring mainly in the Ruvu and Rufiji river systems ( Fig. 1 ). It occurs in the middle and lower reaches of the latter and throughout most of the former but dominantly in the lower reaches. The westernmost locality known to date is in the Kisaki area on the floodplain of the Mgeta River, a tributary of the upper Ruvu River system. There is currently a lack of range data available for the middle reaches of the Ruvu River, but this can probably be attributed to a lack of investigation in that area. The northern extent of distribution is in the southern part of the Wami River delta where it merges with the coastal plains associated with the Ruvu River. The southernmost occurrences are in the coastal floodplains immediately south of the Rufiji delta, probably extending to the lower Matandu River system where a population of what has provisionally been referred to as “ N. cf. janpapi ” is present. The affiliation of this southern population is presently being studied. A single, relatively isolated, occurrence is also known from the Luhule/Luhute River floodplain within the so-called Mbezi Triangle (sensu Watters et al. 2007; Watters 2009).

Conservation status. Nothobranchius janpapi has been evaluated as Least Concern ( Nagy & Watters 2019a). The known extent of occurrence (EOO) is 22,790 km ². Within its area of distribution, the occurrence of the species is fragmented but it seems to be relatively widespread, and it is known from more than 30 threat-based locations in several river drainages. These factors make it the least threatened member of the Aphyobranchius subgenus. However, there is increasing habitat degradation due to expansion of agriculture and urbanisation across its range, including the conversion of some seasonal habitats into permanent ponds (e.g. in the Kwaraza area of the lower Ruvu River system, where the type locality occurs), thereby modifying them in ways that render them unsuitable to support the semi-annual life cycle of the species.

Figures

FIGURE 1. Distribution of species belonging to the subgenus Aphyobranchius, all of which occur in the east-central and southern coastal lowlands of Tanzania: N. janpapi (yellow-filled circle), N. luekei (red-filled triangle), N. geminus (orange-filled diamond), N. lourensi (green-filled square), N. fuscotaeniatus (blue-filled inverted triangle), N. cf. janpapi (dark magenta-filled circle). The inset map shows the area of distribution in a somewhat broader geographic context, to include the distribution of N. willerti (red-filled star) in the lower Tana River area of northeastern coastal Kenya, a species that herein is considered to belong to the subgenus Adiniops, rather than Aphyobranchius to which it was ascribed in the original description by Wildekamp (1992). Note that individual symbols on the map may represent more than one locality or population where the sites are close to one another and could not reasonably be resolved at the scale of the map.

FIGURE 2. Wild-caught specimens of Nothobranchius janpapi and examples of typical habitat. A. N. janpapi Ndundu TAN 95- 10, male, lower Rufiji River drainage; B. N. janpapi Kwaraza TAN 95-14, male, lower Ruvu River drainage, in vicinity of the type locality; C. N. janpapi Soga TAN 97-45, male, Ruvu River drainage; D. N. janpapi Ruvu River TZN 09-4, female, lower Ruvu River drainage (photograph by B. Nagy); E. Location Ruvu River TAN 00-20, a typical thickly vegetated shallow habitat on the floodplain of the lower Ruvu River (photograph June 14, 2000), hosting N. janpapi, N. melanospilus, N. annectens, N. ocellatus and N. eggersi; F. Location Kikale TAN 02-10, thickly vegetated residual pool at a culvert in a seasonal stream course, peripheral to the northern margin of the Rufiji River delta (photograph June 3, 2002), hosting N. janpapi, N. annectens and N. melanospilus. Photographs by B.R. Watters except where otherwise noted.

FIGURE 3. Cephalic structure: a, Nothobranchius janpapi; b, N. luekei; c, N. geminus; d, N. lourensi and N. fuscotaeniatus. Key to label abbreviations: an, anterior nostril; pn, posterior nostril; f, frontal neuromast; so, supraorbital canal; st, supratemporal canal.