THE NOTHOBRANCHIUS SITE

MRAC 97-83-P-1, holotype, male, 32.3 mm SL; Tanzania: Ifakara, interconnected pools in a flooded grassy area, 2 km south of the town of Ifakara on the side of the road to the ferry across the Kilombero River, (08°10' S, 36°42' E); I. F. N. Sainthouse, B. R. Watters & R. H. Wildekamp, 7 Jun 1995 [field code: Ifakara TAN 95-4].

MRAC 97-83-P-2-17 (16)

Nothobranchius geminus is distinguished from all other species of the genus by the combination of following characters: 11–13 dorsal-fin rays; 17–21 anal-fin rays; dorsal fin origin above the mid-length of anal fin base; 6 large neuromasts in the preopercular series; the male has an orange-red spot pattern on the dorsal and anal fins, and an orange-red caudal fin; the female has spots on the head, body and unpaired fins (Wildekamp et al., 2002).

Subgenus: Aphyobranchius

Species group: N. janpapi group

Nothobranchius geminus was established as a species by Wildekamp, Watters & Sainthouse in 2002, and that status has been accorded by all authors since.

Tanzania: Ifakara, interconnected pools in a flooded grassy area, 2 km south of the town of Ifakara on the side of the road to the ferry across the Kilombero River (08°10' S, 36°42' E).

This species is endemic to freshwater habitats in coastal Tanzania. It is known from small seasonal bodies of water associated with the Kibasira swamps in the Kilombero River drainage, eastern Tanzania.

Coastal East Africa (564)

242–347 m

Water parameters based on Watters (personal data) are as follows: temperature of 24–25°C; pH of 7.0–7.6; conductivity of 20–140 µS; and typically turbid (Nagy & Watters, 2019).

N. lucius - 100%

N. lourensi - 89 %

N. kilomberoensis - 67%

This species has an annual life cycle.

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

Maximum size reported: 32.3 mm SL (MRAC 97-83-P-1, holotype, male)

Diploid chromosome number 2n = 38, NF = 40, karyotype structure 2sm+36st/a (Krysanov & Demidova, 2018).

Karyotype structure shared with some other species of the subgenus Aphyobranchius. 

The specific name is formed from the Latin geminus meaning twin or double; in reference to the reflective silver spots in the upper part of the iris apprearing as twin stars and making the fish visible from above when viewed in its natural habitat. An adjective.

Vulnerable B1ab(iii) (Nagy & Watters, 2019);

Previous assessment: Vulnerable D2 (Hanssens & Snoeks, 2006)

​    Wildekamp, R. H., B. R. Watters & I. F. N. Sainthouse. 2002. Two new species of the genus Nothobranchius (Cyprinodontiformes: Aplocheilidae) from the Kilombero River basin, Tanzania. Ichthyological Exploration of Freshwaters, 13 (1): 1–10. [taxonomy as Nothobranchius geminus]

    Nagy, B. & B. R. Watters. 2019. Nothobranchius geminus. The IUCN Red List of Threatened Species: e.T61296A47244197. [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]

    Nagy, B. & B. R. Watters, 2021. A review of the conservation status of seasonal Nothobranchius fishes (Teleostei: Cyprinodontiformes), a genus with a high level of threat, inhabiting ephemeral wetland habitats in Africa. Aquatic Conservation: Marine and Freshwater Ecosystems, 1–18. [conservation]