THE NOTHOBRANCHIUS SITE

MRAC 2019.016.P.0068, holotype, male, 29.5 mm SL; Tanzania: Lake Victoria basin: ephemeral pool on east side of road, 11 km southwest of Chato, 02°42'35" S, 31°43'42" E; B. Nagy, K. Østergaard & G. Petneházy, 1 Jun 2019, [field code: Chato TZN 19-5].

MRAC 2019.016.P.0069–0075 (5), MRAC 2019.016.P.0076 (1)

Nothobranchius venustus belongs to the N. ugandensis species group presenting the following combination of characters in males: body coloration light blue with red or red-brown scale margins; frontal part of head red-brown, throat light blue or red; caudal fin uniform red; and anal fin light blue or yellow with red-brown spotted pattern. Nothobranchius venustus differs from all other members of the N. ugandensis species group by a dorsal fin with a narrow light blue subdistal band and a narrow red-brown to black distal band; an anal fin light blue with irregular red-brown stripes perpendicular to fin rays proximally and medially, and orange with red-brown stripes parallel to fin rays in distal zone; and a dorsal-fin base length 20.4–23.2 % SL (vs. 23.4–28.7) (Nagy et al., 2020).

Subgenus: Zononothobranchius

Species group: N. ugandensis group

​Populations of this species were regarded as part of a diverse complex generally lumped into Nothobranchius species ‘Lake Victoria’, from the basin of that lake in central and western Tanzania and south-western Kenya, together with populations from drainage systems in central Tanzania. Combined morphometric and molecular analyses have revealed that populations from the from the south-western Lake Victoria basin in north-western Tanzania represent a different species, which was described as Nothobranchius venustus by Nagy, Watters & Bellstedt in Nagy et al. (2020).

Tanzania: Lake Victoria basin: ephemeral pool on east side of road, 11 km southwest of Chato, 02°42'35" S, 31°43'42" E.

Nothobranchius venustus is endemic to seasonal freshwater habitats in north-western Tanzania. It is currently known from ephemeral pools and marshes associated with smaller stream systems as part of the Lake Victoria basin, in the southwestern shore region of the lake, and eastwards to the Kongwa River region (Nagy et al., 2020).

Lake Victoria basin (521)

1140–1172 m

At the type locality, the water was turbid, the bottom of the pool not visible. The water temperature measured around noon was 25 °C, the pH was 7.4, and the conductivity was 202 µS (Nagy et al. 2020). Water parameters of another two observations of this species are as follows: temperature 23–28 °C; pH 7.2–8.6; conductivity 40–280 µS; and typically turbid (Watters, personal data in Nagy et al., 2020).

None

This species has a semi-annual life cycle.

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

Maximum size reported: 36.2 mm SL; MRAC 2019.016.P.0076, paratype, male (Nagy et al., 2020)

Diploid chromosome number 2n = 36, NF = 64, karyotype structure 4m+24sm+8st/a (Krysanov et al., 2023).

Karyotype structure unique in the genus, whereas fundamental number unique in the species group.

The specific name venustus, -a, -um is a Latin adjective meaning attractive, charming, graceful, pretty, and is given with reference to the attractive appearance and distinctive coloration of the males.

Vulnerable B1ab(iii)+2ab(iii) (Nagy & Watters, 2021)

    Nagy, B., B. R. Watters, P. D. W. van der Merwe, F. P. D. Cotterill & D. U. Bellstedt. 2020. Review of the Nothobranchius ugandensis species group from the inland plateau of eastern Africa with descriptions of six new species (Teleostei: Nothobranchiidae). Ichthyological Exploration of Freshwaters, 30 (1): 21–73. [taxonomy as Nothobranchius venustus, distribution, ecology, phylogeny, systematics]

    Nagy, B. 2020. An expedition around Lake Victoria. Tropical Fish Hobbyist, #744, Sep/Oct 2020, 69 (1): 44–50. [collecting]

    Nagy, B. 2020. Lands of the unknown Nothobranchius. Practical Fishkeeping, 2020 (12): 24–31. [collecting]

    Nagy, B. & B. R. Watters. 2021. Nothobranchius venustus. The IUCN Red List of Threatened Species: e.T175184958A175184965. [conservation]

    Krysanov, E. Y., B. Nagy, B. R. Watters, A. Sember & S. A. Simanovsky. 2023. Karyotype differentiation in the Nothobranchius ugandensis species group (Teleostei, Cyprinodontiformes), seasonal fishes from the east African inland plateau, in the context of phylogeny and biogeography. Comparative Cytogenetics, 17 (1): 13–29. [chromosomes]