THE NOTHOBRANCHIUS SITE

ZMB 14485, holotype, male, 52.0 mm TL, Sumpfbay Tschangarra, Nord Usinja, Tanzania; colleced by F. Stuhlmann, 7 Mar 1892. [unique, lost]

"Die Art unterscheidet sich von den nächstverwandten Arten leicht durch die weiter nach dem Kopf zu eingelenkte Dorsale" (Ahl, 1935).

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A medium-sized and deep bodied Nothobranchius with pointed snout and slightly convex dorsal-head transition. Dorsal and anal fins large. Origin of dorsal fin in front of, or opposite to, origin of anal fin. Extremely small papillae on dorsal and anal fin rays in males. Male almost completely red (Wildekamp, 1994).

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Nothobranchius robustus males are characterized by pale blue scales with narrow red margins at the anterior part of the trunk, usually resulting in the blue body colour becoming increasingly red towards the posterior part of the body where wide scale margins result in an almost completely red colouration. The unpaired fins and the ventral fins are completely red. The caudal fin usually has a narrow black margin. The intensity of the general red colouration may vary across populations.

Females are yellow-brown, with transparent fins.

Subgenus: Zononothobranchius

Nothobranchius robustus was established as a species by Ahl in 1935. It was described from a single male specimen collected by F. Stuhlmann on 7 March 1892 from a locality spelled as ‘Sumpfbay Tschangarra’ in Ahl (1935). The unique holotype is considered lost (Paepke & Seegers, 1986). The type locality of N. robustus was described by Wildekamp (1980) as a swampy extension of Nungwe Bay, on the eastern shore of Emin Pascha Gulf, east of the village Nungwe, and by Sainthouse (1989) as the Tschamgaera Creek, approximately 2 km southwest of the village Kinunga, spelling and information taken from the detailed route map of Stuhlmann (1894). Following the detailed map, Nagy et al. (2020) estimated the type locality to approximately 02°43' S, 32°28' E.

As pointed out by Nagy & Watters (2018) and Nagy et al. (2020), some uncertainty exists regarding the identity of this species. Since the original collection at the type locality in 1892, the species has not been found again in Tanzania and all other known occurrences of what have been regarded as representatives of this species consist of records from Uganda (Wildekamp, 1994). The limited morphometric a meristic information provided in the original description of Ahl (1935) is not conclusive and are, in general, comparable to those of N. robustus from Uganda (Wildekamp (1994).

Live coloration as provided by Stuhlmann in the original description, can be translated as: “light blue, with brown scale margins on the body with brownish red fins”, which agrees with field observations, particularly in reference to the uniform brown-red coloration of the fins.

Specimens collected in Uganda that are presently referred to as N. robustus, are not differing significantly from that described by Ahl (1935) and are considered to be conspecific (Wildekamp,1994; Nagy et al., 2020).

Sumpfbay Tschangarra, Nord Usinja, Tanzania.

This species is endemic to seasonal freshwater habitats in southern and western Uganda, south-western Kenya and north-western Tanzania. In Uganda, the species is known from temporary rivers, pools and papyrus swamps in the drainage systems of Lake Victoria, Lake Kyoga, the Victoria Nile River, Lake Albert and the Kafu River, and the Katonga River system that drains into Lakes George and Edward. It also inhabits the drainage system of the Sio River in western Kenya, near Lake Victoria and very close to the border with Uganda. The type locality is situated in the drainage system of Lake Victoria in northwestern Tanzania.

Lake Victoria basin (521)

1047–1210 m

Personal observation at collecting sites (12 locations):

Water temperature: 21.8–27.3 °C (average: 24.5 °C)

pH: 6.17–7.16 (average: 6.50)

TDS:  25–198 ppm (average: 94 ppm)

Conductivity: 50–396 µS (average: 188 µS)

N. ugandensis - 8%

This species has a semi-annual life cycle.

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

Maximum size reported: 39.2 mm SL (MRAC 93-159-P-46-48, males); 52 mm TL (Ahl, 1935); 51 mm TL (Nagy et al., 2020)

Diploid chromosome number 2n = 36, NF = 58, karyotype structure 4m+18sm+14st/a (Krysanov & Demidova, 2018).

Diploid chromosome number and karyotype structure shared with N. capriviensis.

The specific name is formed from robustus (in Latin for robust, strong), in reference to the body shape of the species, in comparison to its congeners.

Least Concern (Nagy & Watters, 2019);

Previous assessment: Least Concern (FishBase team RMCA & Geelhand, 2016);

Data Deficient (IUCN Red List 2006)

    Ahl, E. 1935. Über neue oder seltene afrikanische Zahnkarpfen der Gattungen Aphyosemion und Nothobranchius. Zoologischer Anzeiger, 112: 123–129. [taxonomy as Nothobranchius robustus]

    Wildekamp, R.H. 1994. The Nothobranchius species from Uganda, with description of a new polymorphic species (Cyprinodontiformes: Aplocheilidae). Ichthyological ExpIorations of Freshwaters, 5 (3): 193–206. [systematics]

    Nagy, B. 2010. Collecting Nothobranchius in 'The pearl of Africa'.  Nothobranchius Archives, 1 (1): 14–30. [collecting, distribution, ecology]

    Nagy, B. 2015. Life history and reproduction of Nothobranchius fishes. Journal of the American Killifish Association, 47 (4–6): 182–192. [ecology]

    Nagy. B. 2017. Searching for a mystery Nothobranchius in Uganda. Journal of the American Killifish Association, 50 (6): 162–174. [collecting]

    Nagy, B. & B. R. Watters. 2018. Distribution and habitat conditions of Nothobranchius fishes in Uganda. Journal of the American Killifish Association, 51 (5–6): 176–192. [distribution, ecology]

    Nagy, B. & B. R. Watters. 2019. Nothobranchius robustus. The IUCN Red List of Threatened Species 2019: e.T60434A131472275. [conservation]

    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. [phylogeny, systematics]

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