THE NOTHOBRANCHIUS SITE

BE_RMCA_VERT.2025.008.P.0039, male, 22.5 mm SL; DR Congo: Kay system: upper Lualaba drainage: shallow remnant pool in small seasonal riverbed, 0.5 km west of Lubule village, 07°31'47" S, 27°13'24" E; B. Katemo Manda, 17 Apr 2023 (field code: CD 23-26).

BE_RMCA_VERT.2025.008.P.0040–0043 (4) BE_RMCA_VERT.2025.008.P.0044 (1).

'Lacustricola' gemma is distinguished from all other species of the genus by the unique combination in live colouration: in males, a pattern of iridescent, diamond-shaped, light blue spots in scale centres, especially evident below mid-longitudinal series on posteroventral portion of flank, and larger iridescent blue blotches on dorsum, creating an irregular reflective pattern on body; median fins yellow to hyaline, dorsal and anal fins with six to eight dark grey stripes perpendicular to fin rays basally and posteriorly, with light blue iridescence basally; dorsal with light blue distinct margin; anal with dark grey margin; caudal fin with four to five dark grey stripes perpendicular to fin rays; as well as in females, dorsal and anal fins hyaline with irregular brown stripes, fin tips with narrow light blue margin, caudal hyaline without markings.

Genus: Southern African 'Lacustricola'

Species group: 'L'. hutereaui group

'Lacustricola' gemma was established as a species by Nagy in 2025.

DR Congo: Kay system: upper Lualaba drainage: shallow remnant pool in small seasonal riverbed, 0.5 km west of Lubule village, 07°31'47" S, 27°13'24" E, 634 m alt.

This species is endemic to seasonal freshwater habitats of the upper Congo drainage in south-eastern DR Congo. It is currently known from remnant pools in small ephemeral riverbeds associated with the Kay system in the upper Lualaba drainage. The Kay is a major right bank affluent entering the upper Lualaba below Lake Upemba.

Upper Lualaba (545)

634 m

Water parameters, measured by B. Katemo Manda at two sites: 27.3 and 28.4 °C; 30 and 120 ppm; pH of 7.2.

None

The species has a non-annual mode of reproduction, the same as all of its known congeners. An embryonic development period of about two to three weeks was observed at about 22–24 °C. 

Maximum size reported: 23.0 mm SL (BE_RMCA_VERT.2025.008.P.0040–0043, paratype, male)

Not known

The specific epithet gemma is derived from the ancient Greek word γέμω, originally meaning “precious stone” or “gem.” It refers to the pattern of the body scales, which are adorned with numerous iridescent, diamond-shaped markings, evoking the appearance of tiny gems. The name also alludes to the relatively small adult size of the species. It is treated as a noun in the nominative singular, standing in apposition to the generic name.

Not evaluated

Recommended as Vulnerable in Nagy, 2025.

    Nagy, B. 2025. Review of cyprinodontiform fishes in the upper Congo drainage with descriptions of four new species of seasonal Nothobranchius (Nothobranchiidae) and a new species of ‘Lacustricola’ Lampeye (Procatopodidae) in South-Eastern DR Congo. Ecology and Diversity, 2 (2), 10006. [taxonomy as Nothobranchius katemomandai, distribution, ecology]