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Lake Victoria is home to a unique and taxonomically understudied species flock of endemic haplochromine cichlid fishes, with many morphologically specialized trophic groups and many different species in each of them. One of several mollusk-eating trophic groups are the pharyngeal snail-crushers of the genus Labrochromis Regan, 1920. Currently, six species from Lake Victoria have been described in this genus, none of which occupies rocky shores and reefs. Rocky shores and reefs of Lake Victoria, however harbor rich assemblages of habitat-specialized cichlids and these include snail-crushers. Here two new species of Labrochromis are described from this habitat in the Southeastern part of Lake Victoria. These species are distinct in their ecology, morphology, and male nuptial coloration from all previously described Labrochromis species, and they are distinct from each other in oral dentition, morphology, and stripe pattern. These species are named Labrochromis mawe sp. nov. and Labrochromis mawepili sp. nov. Both are currently only known from the Mwanza and Speke Gulf regions of the lake in Tanzania.

Background The Lake Victoria basin is one of the most persistent hotspots of schistosomiasis in Africa, the intestinal form of the disease being studied more often than the urogenital form. Most schistosomiasis studies have been directed to Schistosoma mansoni and their corresponding intermediate snail hosts of the genus Biomphalaria , while neglecting S. haematobium and their intermediate snail hosts of the genus Bulinus . In the present study, we used DNA sequences from part of the cytochrome c oxidase subunit 1 ( cox 1) gene and the internal transcribed spacer 2 (ITS2) region to investigate Bulinus populations obtained from a longitudinal survey in Lake Victoria and neighbouring systems during 2010–2019. Methods Sequences were obtained to (i) determine specimen identities, diversity and phylogenetic positions, (ii) reconstruct phylogeographical affinities, and (iii) determine the population structure to discuss the results and their implications for the transmission and epidemiology of urogenital schistosomiasis in Lake Victoria. Results Phylogenies, species delimitation methods (SDMs) and statistical parsimony networks revealed the presence of two main groups of Bulinus species occurring in Lake Victoria; B. truncatus / B. tropicus complex with three species ( B. truncatus , B. tropicus and Bulinus sp. 1), dominating the lake proper, and a B. africanus group, prevalent in banks and marshes. Although a total of 47 cox 1 haplotypes, were detected within and outside Lake Victoria, there was limited haplotype sharing (only Haplotype 6 was shared between populations from Lake Victoria open waters and neighbouring aquatic systems) – an indication that haplotypes are specific to habitats. Conclusions The Bulinus fauna of Lake Victoria consists of at least B. truncatus , B. tropicus , Bulinus sp. 1 ( B. trigonus ?) and B. ugandae . The occurrence and wide distribution of Bulinus species in Lake Victoria potentially implies the occurrence of urogenital schistosomiasis in communities living along the shores and on islands of the lake who depend solely on the lake for their livelihood. More in-depth studies are needed to obtain a better picture of the extent of the disease in the Lake Victoria basin.

Background Snails such as Galba truncatula are hosts for trematode flukes causing fascioliasis, a zoonosis that is a major public health problem. Galba truncatula has recently been shown to be a cryptic species complex. African populations of Galba spp. are not yet studied using molecular assessments and is imperative to do so and reconstruct the centre of origin of Galba and to understand when and by what means it may have colonized the highlands of Africa and to what extent humans might have been involved in that process. Methods Samples from all known sub-ranges throughout Africa and new samples from Europe and Asia were obtained. We used a combination of two mitochondrial ( cox 1 and 16S ) and one nuclear (ITS2) markers and phylogenetic, divergence time estimates and phylogeographical methods to determine the identity and biogeographical affinities. We also reconstructed the colonization history including the likely mode of dispersal and tested for the presence of cryptic Galba species in Africa. Results Galba truncatula is restricted to the Palaearctic region of the continent, namely Morocco. All sub-Saharan populations proved to be a distinct species according to the phylogenetic analyses and genetic distance. We propose to use the existing name Galba mweruensis (Connolly, 1929) for this species which is morphologically indistinguishable from the other two species hitherto known to occur in northern Africa, i.e. G. truncatula and G. schirazensis . Sub-tropical Africa has been colonized only once in either the Pliocene and possibly Miocene. Diversification within G. mweruensis is dated to the Plio-Pleistocene and thus human-mediated dispersal can be ruled out for the initial colonization of the isolated mountain ranges. There are potentially even more cryptic species in high altitude areas of Africa as outlined by the distinctness of the population found at the top of Mt. Elgon, Uganda. Conclusions From a novel genetic inspection of available African material, a hitherto neglected distinct species, G. mweruensis , now appears a major host of F. hepatica throughout sub-Saharan Africa. A closer examination of trematode parasites hosted by this species is needed in order to understand transmission patterns in highlands throughout eastern and southern Africa. We encourage future studies to inspect other high altitudes areas in Africa in light of parasites of either veterinary or medical importance.

Speciation often emerges from the complex interplay of geography, demography, ecology, and sexual selection, yet disentangling their relative contributions remains a challenge. In this study, we examine two species complexes of rock-dwelling Lake Victoria cichlids in the genera Pundamilia and Neochromis that are distributed along a continuous geographic gradient of rocky shores. Using morphometric analyses and male nuptial coloration data, we reveal clinal craniofacial divergence following an isolation by distance model of evolution, punctuated by strong local effects. While the Pundamilia cline exhibited modular shifts in craniofacial anatomy linked to diet-specific morphology, variation in the Neochromis cline was dominated by allometric constraints, suggesting different evolutionary processes at play. At the single site where the terminal populations of both clines co-occur, each pair of sister species showed pronounced divergence in morphology and male nuptial coloration, consistent with ecological and sexual character displacement facilitating co-existence. Our findings highlight that clinal morphological variation in parapatry and more abrupt shifts in sympatry interact to generate and maintain species. These rocky shore cichlids provide a rare opportunity to investigate the speciation continuum in one of the world’s youngest adaptive radiations.