THE NOTHOBRANCHIUS SITE

MRAC 2019.005.P.0004, holotype, male 41.5 mm SL; Tanzania: remnant pools alongside the road, about 33 km S of Tabora, 05°20.8' S, 32°41.5' E; H. Hengstler, S. Hengstler & W. Krammer, 28 Apr 2018, [field code: Tabora TZHK 2018-02].

MRAC 2019.005.P.0005-9 (5)

Nothobranchius sonjae is distinguished from all other species of the genus by the following characters in males: body coloration light blue to blue-green with red-brown, brown or grey scale margins and a golden-brown to grey stripe on the dorsal scale row between nape and dorsal-fin origin. Anal fin light blue-grey to yellow-grey with irregular red to red-brown spots proximally, followed by a narrow brown submedial band, a slender yellow medial band and a broad black distal band. Caudal fin yellow-brown, grey-brown, blue-grey or grey, with red-brown, brown, dark grey or red spots; some populations with radiating red stripes, the density of which varies from moderate to highly dense such that in the latter cases the basal, proximal and medial zones may appear dominantly a deep red; distal zone comprises a slender to broad semi-translucent dark grey to black distal band. Pelvic fin light blue-grey to yellow-grey, with broad yellow medial band and narrow black and blue distal margin. Furthermore, it differs from the other members of the N. taeniopygus species group in central and western Tanzania by a head length of 25.8-27.0 % SL (vs. 27.3-34.6); and caudal peduncle length 153-159 % of its depth (vs. 119-149 and 160-169, respectively) (Watters et al., 2019).

​Subgenus: Zononothobranchius

Species group: N. taeniopygus group

Populations of this species were referred to N. taeniopygus, based on some general similarities of colour pattern with that species. Since the redescription by Wildekamp (1990), many more populations of members of the N. taeniopygus group across a wide distribution range in western and central Tanzania. These resulted in the name N. taeniopygus or N. aff. taeniopygus being attached to various populations, and notable differences, primarily in colour pattern, led to the informal designation of numerous ‘phenotypes’ by Wildekamp (2004).

Populations of this species had been regarded as representing ‘phenotype 2’ (Wildekamp, 2004). Morphometric and molecular analyses confirmed the distinction from N. taeniopygus and the species was described as N. sonjae by Watters, Nagy & Bellstedt in Watters et al. (2019).

Tanzania: remnant pools alongside the road, about 33 km S of Tabora, 05°20.8' S, 32°41.5' E.

This species is endemic to west-central Tanzania. It is known from seasonal pools and marshes primarily associated with the Malagarasi River drainage, including mainly the Ugalla River system and its tributaries, the Wala and Nkululu rivers in particular, and the Gombe/Igombe river system and associated tributaries. At least one locality exists outside of the present Malagarasi basin, associated with the Moame River that drains into Lake Victoria via the Mwanza Gulf. Many of the presently known sites are in the vicinity of Tabora. The type locality is situated in the Wala drainage.

Malagarasi–Moyowosi (543)

1037–1338 m

Water parameters (Watters, personal data): temperature of 22°C; pH of 7.5–8.3; conductivity of 120-380 µS; and turbid (Nagy & Watters, 2020).

N. seegersi - 24%

N. neumanni - 10%

N. hoermanni - 5%

This species has an annual life cycle.

Embryonic development under captive conditions in peat moss is about three to six months at room temperature.

Maximum size reported: 43.8 mm SL; MRAC 2019.005.P.0009, paratype, male (Watters et al., 2019)

Not known

The specific name is given in honour of Sonja Hengstler, co-collector of the type specimens of this species-name. She is an active participant and plays an essential role in Nothobranchius collecting trips in Africa together with his husband, the renowned killifish enthusiast, Holger Hengstler. A noun in genitive.

Least Concern (Nagy & Watters, 2020)

    Watters, B. R., B. Nagy, P. D. W. van der Merwe, F. P. D. Cotterill & D. U. Bellstedt. 2019. Review of the Nothobranchius taeniopygus species group from central and western Tanzania with descriptions of five new species and redescription of Nothobranchius taeniopygus (Teleostei: Nothobranchiidae). Ichthyological Exploration of Freshwaters, 29 (3): 239–278. [taxonomy as Nothobranchius sonjae, distribution, ecology, phylogeny, systematics]

    Nagy, B. & B. R. Watters. 2020. Nothobranchius sonjae. The IUCN Red List of Threatened Species: e.T156302263A156302289.