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

The cyprinodontiform fish fauna of the Bangweulu–Mweru and Upper Lualaba freshwater ecoregions, situated in the uppermost Congo River drainage, has been reviewed. This study introduces four newly described species of seasonal Nothobranchius killifish and a novel species of lampeye belonging to the genus ‘Lacustricola’. Nothobranchius iridescens, new species, from the Kafila system in the Lufira drainage, is characterized in male colouration by anal fin with irregular red-brown spots and stripes, creating two irregular submedial and medial bands and with broad yellow subdistal band; and a caudal fin with a slender light blue subdistal band, densely marked with irregular red spots, and narrow dark brown distinct distal margin. Nothobranchius katemomandai, new species, from the Kay system in the upper Lualaba drainage, is characterized in male colouration by an anal fin with narrow brown submedial band, followed by a slender yellow band, a slender red-brown band and a slender dark brown distal band; and a caudal fin with brown spots proximally and medially, and with slender white to light blue subdistal band and a narrow dark grey distal band. Nothobranchius marmoreus, new species, from the Lufukwe system in the Lake Mweru basin, is characterized in male colouration by a body with irregular red-brown patches and stripes, forming a marble-like mottled pattern; and anal and caudal fins with slender yellow to amber subdistal band and broad dark brown distal band. Nothobranchius dubieensis, new species, from the Lubule system in the Luvua drainage, is characterized in male colouration by an anal fin with narrow dark brown submedial band, narrow yellow and orange medial bands, narrow white subdistal band, and slender dark brown distal band; and a caudal fin with irregular red-brown spots and stripes proximally and medially, followed by an irregular narrow red-brown subdistal band and slender white distal band, and with interrupted red-brown fin tips. ‘Lacustricola’ gemma, new species, from the Kay system in the upper Lualaba drainage, is characterized by a pattern of iridescent, diamond-shaped, light blue spots in scale centres below mid-longitudinal series on posteroventral portion of flank; median fins yellow to hyaline, with dark grey stripes perpendicular to fin rays; dorsal fin with light blue distinct margin; anal fin with dark grey margin. Analysis of mitochondrial COI gene sequences revealed that the five new species represent phylogenetically distinct lineages. These findings not only underscore their genetic uniqueness but also confirm their placement within the Nothobranchius brieni species group and the genus ‘Lacustricola’. Species of the genus Nothobranchius complete their seasonal life cycle in ephemeral natural habitats within freshwater wetlands, while ‘Lacustricola’ species migrate to breed in flooded areas of shallow, typically seasonal wetland habitats at the onset of the rainy season. These wetlands are highly vulnerable to a variety of human-induced stressors and threats, including agricultural cultivation, water extraction, urban expansion resulting in land-use pressure, and increased pollution, particularly from industrial activities such as mining. Therefore, it is essential to protect the integrity of these unique aquatic habitats throughout all the seasons of the year to maintain healthy wetland ecosystems and safeguard the distinctive seasonal freshwater biodiversity they support.