Nothobranchius poppi, new species

Nothobranchius poppi, new species, described from ephemeral wetlands in the upper Lubi River system, a left bank affluent of the lower Luapula River drainage (upper Congo River drainage) in the Democratic Republic of the Congo. It is identified as belonging to the N. brieni species group that is endemic to the upper Congo River and upper and middle Zambezi River drainages in south-central Africa. Members of this species group are characterised by a combination of colour pattern features in the male: light blue scales with broad brown-red borders creating a reticulated pattern on body; brown-red spots on proximal portion of median fins; and, caudal and anal fins with either a pattern of dark distal and light subdistal bands or, on the caudal fin an overlaying light blue iridescent distal band. Nothobranchius poppi is distinguished from all other members of this species group by: (i) a unique colour pattern in the male combining median fins with an irregular red-brown reticulated pattern and an overlaying light blue iridescent distal band; an anal fin lacking a subdistal band but having, rather, a narrow red-brown margin on fin-ray tips; (ii) significant differences in morphometric and meristic characters; (iii) molecular analysis of the mitochondrial COI barcoding gene, identifying a phylogenetically distinct lineage; and (iv) unique cytogenetic characteristics showing a multiple sex chromosome system with diploid number 2n = 49 for males and 2n = 50 for females. Nothobranchius poppi, like all congeners, completes its seasonal life cycle in ephemeral freshwater wetlands, making it highly vulnerable to habitat degradation. These wetlands are increasingly threatened by human activities such as agriculture, water abstraction, urban expansion, industrial pollution, and mining. Protecting the integrity of these habitats year-round is essential to preserve their unique seasonal biodiversity. The description of this new species from the lower Luapula River drainage aims to highlight the urgent need for stronger freshwater wetland conservation efforts by both national and international stakeholders.