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Background: Monogenean parasites have never been formally reported on fishes from the Lufira River Basin. In this context, we decided to record the monogenean parasite fauna of three cichlid species found in the Upper Lufira River Basin for the first time by inventorizing their diversity (species composition) and analysing their infection parameters (prevalence, mean intensity and abundance)., Methods: The African cichlid fishes Oreochromis mweruensis, Coptodon rendalli and Serranochromis macrocephalus were selected for the study, given their economic value and their abundance in the Upper Lufira River Basin. Monogeneans were isolated from the gills and stomach, mounted on glass slides with either Hoyer's medium or ammonium picrate-glycerin for identification under a stereomicroscope, based on morphological analysis of genital and haptoral hard parts. Indices of diversity and infections parameters were calculated., Results: A total of 13 gill monogenean parasite species (Cichlidogyrus dossoui, C. halli, C. karibae, C. mbirizei, C. papernastrema, C. quaestio, C. sclerosus, C. tiberianus, C. tilapiae, C. zambezensis, Scutogyrus gravivaginus, S. cf. bailloni and Gyrodactylus nyanzae) and one stomach monogenean (Enterogyrus malmbergi) were identified. A species richness (S) of 10 for O. mweruensis, S = 6 for C. rendalli and S = 2 for S. macrocephalus was recorded. Five parasite species were reported to be common amongst O. mweruensis and C. rendalli. According to cichlid species, the most prevalent parasite species was C. halli (prevalence [P] = 80.9%) on O. mweruensis, C. dossoui (P = 92.9%) on C. rendalli and C. karibae and C. zambezensis (both P = 9.1%) on S. macrocephalus. The parasite species with the highest mean intensity (MI) were G. nyanzae (MI = 8.7) on O. mweruensis, C. papernastrema (MI = 17.1) on C. rendalli and C. karibae (MI = 15) on S. macrocephalus. The findings indicate new host ranges for five parasites species (C. quaestio, S. cf. bailloni, E. malmbergi on O. mweruensis, C. halli on C. rendalli and C. karibae on S. macrocephalus) as well as new geographical records for all of them as they are recorded for the first time in the Lufira River Basin., Conclusions: This study highlighted the richness of monogenean communities in the Upper Lufira River Basin and is a starting point for future helminthological studies, such as on the use of fish parasites as indicators of anthropogenic impacts., (© 2023. The Author(s).)

During colonial times, Nile tilapia Oreochromis niloticus (Linnaeus, 1758) was introduced into non-native parts of the Congo Basin (Democratic Republic of the Congo, DRC) for the first time. Currently, it is the most farmed cichlid in the DRC, and is present throughout the Congo Basin. Although Nile tilapia has been reported as an invasive species, documentation of historical introductions into this basin and its consequences are scant. Here, we study the genetic consequences of these introductions by genotyping 213 Nile tilapia from native and introduced regions, focusing on the Congo Basin. Additionally, 48 specimens from 16 other tilapia species were included to test for hybridization. Using RAD sequencing (27,611 single nucleotide polymorphisms), we discovered genetic admixture with other tilapia species in several morphologically identified Nile tilapia from the Congo Basin, reflecting their ability to interbreed and the potential threat they pose to the genetic integrity of native tilapias. Nile tilapia populations from the Upper Congo and those from the Middle-Lower Congo are strongly differentiated. The former show genetic similarity to Nile tilapia from the White Nile, while specimens from the Benue Basin and Lake Kariba are similar to Nile tilapia from the Middle-Lower Congo, suggesting independent introductions using different sources. We conclude that the presence of Nile tilapia in the Congo Basin results from independent introductions, reflecting the dynamic aquaculture history, and that their introduction probably leads to genetic interactions with native tilapias, which could lower their fitness. We therefore urge avoiding further introductions of Nile tilapia in non-native regions and to use native tilapias in future aquaculture efforts., (© 2022 John Wiley & Sons Ltd.)

Haplochromis pharyngalis and Haplochromis petronius, two endemic cichlids from the Lake Edward system (Uganda, Democratic Republic of the Congo), are very similar in general morphology but have been reported to differ in pharyngeal jaw morphology and distribution. This study analysed 51 morphometrics and various qualitative characteristics of 48 specimens from different localities. The morphological traits of both species strongly overlap, and differences in the pharyngeal jaw morphology correspond to a geographic morphocline. We conclude that all specimens belong to one valid species, H. pharyngalis, and consider H. petronius to be a synonym., (© 2020 The Fisheries Society of the British Isles.)

Lake Edward, East Africa, harbours a largely understudied assemblage of haplochromine cichlids that displays a range of adaptions to various specialised trophic niches. In this system, we discovered specimens of Haplochromis with morphologies similar to those of oral-mollusc shellers from Lake Victoria. These morphologies are characterised by short oral jaws with stout teeth that are used either to crush molluscs or to grab the soft bodies of snails and wrench them out of their shells. A morphometric study on 47 specimens from Lake Edward revealed the presence of three new species with an oral-shelling morphology: Haplochromis concilians sp. nov., H. erutus sp. nov. and H. planus sp. nov. All three species are formally described. Stomach-content observations confirmed an opportunistic oral-shelling ecology for H. concilians sp. nov. and H. erutus sp. nov. Within H. planus sp. nov., only large specimens displayed a specialised oral-shelling morphology, but their stomachs were nearly empty, while small specimens consumed mainly Ostracoda and Hydrachnidia. Remarkably, the three species differed considerably in morphology from each other, but they each resembled oral-sheller species from Lake Victoria., (© 2019 The Fisheries Society of the British Isles.)

Since prezygotic rather than postzygotic barriers are believed to maintain the diversity of closely related sympatric cichlids, differences in phenotypic traits and reproductive behaviours are likely involved in maintaining species boundaries. Here, we focused on the reproductive behaviour of three Ophthalmotilapia species with distributions that only overlap on a small stretch of the shore line of Lake Tanganyika. Repeated introgression of mitochondrial DNA between these species was previously reported, which suggested they can hybridise. Our aim is to test the hypothesis that reproductive behaviour acts as a prezygotic barrier that prevents frequent hybridisation in sympatric Ophthalmotilapia species. We performed a quantitative analysis of twelve reproductions (four for O. ventralis, six for O. nasuta, one for O. boops, and one between a female O. ventralis and a male O. nasuta). Although similar ethograms were obtained for these reproductions, the O. ventralis and O. boops males displayed a behaviour that was never performed by O. nasuta males. This behaviour was displayed during courtship and we called it 'invite'. In O. ventralis, we could show that it was associated with the emission of a single pulse sound. The comparison of O. nasuta and O. ventralis reproductive behaviours also revealed some quantitative differences: O. ventralis males showed the location of the bower more often to the female, whereas O. ventralis females followed the male more often. The similarity between the reproductive behaviours in O. ventralis and O. nasuta could explain the occurrence of the heterospecific spawning event recorded between an O. nasuta male and an O. ventralis female. Importantly, few eggs were laid and the maternal mouthbrooding that resulted from this heterospecific reproduction only lasted for two days, which suggested the abortion of egg development. Hence, in the absence of conspecifics, courtship and mating behaviours alone do not constitute perfect prezygotic barriers between these two species., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

The Lower Congo Basin is characterized by a mangrove-lined estuary at its mouth and, further upstream, by many hydrogeographical barriers such as rapids and narrow gorges. Five localities in the mangroves and four from (upstream) left bank tributaries or pools were sampled. On the gills of Coptodon tholloni, Coptodon rendalli, Hemichromis elongatus, Hemichromis stellifer and Tylochromis praecox, 17 species of parasites (Dactylogyridae & Gyrodactylidae, Monogenea) were found, eight of which are new to science. Six of these are herein described: Cichlidogyrus bixlerzavalai n. sp. and Cichlidogyrus omari n. sp. from T. praecox, Cichlidogyrus calycinus n. sp. and Cichlidogyrus polyenso n. sp. from H. elongatus, Cichlidogyrus kmentovae n. sp. from H. stellifer and Onchobdella ximenae n. sp. from both species of Hemichromis. On Cichlidogyrus reversati a ridge on the accessory piece was discovered that connects to the basal bulb of the penis. We report a putative spillback effect of the native parasites Cichlidogyrus berradae, Cichlidogyrus cubitus and Cichlidogyrus flexicolpos from C. tholloni to the introduced C. rendalli. From our results, we note that the parasite fauna of Lower Congo has a higher affinity with the fauna of West African and nearby freshwater ecoregions than it has with fauna of other regions of the Congo Basin and Central Africa., (© M.W.P. Jorissen et al., published by EDP Sciences, 2018.)

Pseudocrenilabrus pyrrhocaudalis sp. nov. is described from Lake Mweru in the upper Congo River drainage, on the border of the Democratic Republic of Congo and Zambia. This species, which appears to be endemic to the lake, lives in sympatry with P. philander. Pseudocrenilabrus pyrrhocaudalis sp. nov. is distinguished from P. philander in nuptial males by the presence of an orange colour on the ventral part of the body and the proximal parts of the anal and caudal fins, a broad band of bright white on the distal edge of anal and caudal fins, a uniform grey head and dorsum, and a subtruncate caudal fin. In addition, P. pyrrhocaudalis has a shorter snout, a narrower head, a smaller interorbital distance, a smaller pre-anal distance, a more slender caudal peduncle and fewer scales around the caudal peduncle in both sexes.

We obtained 398 cytochrome c oxidase subunit I barcodes of 96 morphospecies of Lake Tanganyika (LT) cichlids from the littoral zone. The potential of DNA barcoding in these fishes was tested using both species identification and species delineation methods. The best match (BM) and best close match (BCM) methods were used to evaluate the overall identification success. For this, three libraries were analysed in which the specimens were categorized into Operational Taxonomic Units (OTU) in three alternative ways: (A) morphologically distinct, including undescribed, species, (B) valid species and (C) complexes of morphologically similar or closely related species. For libraries A, B and C, 73, 73 and 96% (BM) and 72, 70 and 94% (BCM) of the specimens were correctly identified. Additionally, the potential of two species delineation methods was tested. The General Mixed Yule Coalescent (GMYC) analysis suggested 70 hypothetical species, while the Automatic Barcode Gap Discovery (ABGD) method revealed 115 putative species. Although the ABGD method had a tendency to oversplit, it outperformed the GMYC analysis in retrieving the species. In most cases where ABGD suggested oversplitting, this was due to intraspecific geographical variation. The failure of the GMYC method to retrieve many species could be attributed to discrepancies between mitochondrial gene trees and the evolutionary histories of LT cichlid species. Littoral LT cichlids have complex evolutionary histories that include instances of hybridization, introgression and rapid speciation. Nevertheless, although the utility of DNA barcoding in identification is restricted to the level of complexes, it has potential for species discovery in cichlid radiations., (© 2016 John Wiley & Sons Ltd.)

The stunning diversity of cichlid fishes has greatly enhanced our understanding of speciation and radiation. Little is known about the evolution of cichlid parasites. Parasites are abundant components of biodiversity, whose diversity typically exceeds that of their hosts. In the first comprehensive phylogenetic parasitological analysis of a vertebrate radiation, we study monogenean parasites infecting tropheine cichlids from Lake Tanganyika. Monogeneans are flatworms usually infecting the body surface and gills of fishes. In contrast to many other parasites, they depend only on a single host species to complete their lifecycle. Our spatially comprehensive combined nuclear-mitochondrial DNA dataset of the parasites covering almost all tropheine host species (N = 18), reveals species-rich parasite assemblages and shows consistent host-specificity. Statistical comparisons of host and parasite phylogenies based on distance and topology-based tests demonstrate significant congruence and suggest that host-switching is rare. Molecular rate evaluation indicates that species of Cichlidogyrus probably diverged synchronically with the initial radiation of the tropheines. They further diversified through within-host speciation into an overlooked species radiation. The unique life history and specialisation of certain parasite groups has profound evolutionary consequences. Hence, evolutionary parasitology adds a new dimension to the study of biodiversity hotspots like Lake Tanganyika.

The unparalleled biodiversity of Lake Tanganyika (Africa) has fascinated biologists for over a century; its unique cichlid communities are a preferred model for evolutionary research. Although species delineation is, in most cases, relatively straightforward, higher-order classifications were shown not to agree with monophyletic groups. Here, traditional morphological methods meet their limitations. A typical example are the tropheine cichlids currently belonging to Simochromis and Pseudosimochromis. The affiliations of these widespread and abundant cichlids are poorly understood. Molecular work suggested that genus and species boundaries should be revised. Moreover, previous morphological results indicated that intraspecific variation should be considered to delineate species in Lake Tanganyika cichlids. We review the genera Simochromis and Pseudosimochromis using an integrative approach. Besides a morphometric study and a barcoding approach, monogenean Cichlidogyrus (Platyhelminthes: Ancyrocephalidae) gill parasites, often highly species-specific, are used as complementary markers. Six new species are described. Cichlidogyrus raeymaekersi sp. nov., C. muterezii sp. nov. and C. banyankimbonai sp. nov. infect S. diagramma. Cichlidogyrus georgesmertensi sp. nov. was found on S. babaulti and S. pleurospilus, C. franswittei sp. nov. on both S. marginatus and P. curvifrons and C. frankwillemsi sp. nov. only on P. curvifrons. As relatedness between Cichlidogyrus species usually reflects relatedness between hosts, we considered Simochromis monotypic because the three Cichlidogyrus species found on S. diagramma belonged to a different morphotype than those found on the other Simochromis. The transfer of S. babaulti, S. marginatus, S. pleurospilus and S. margaretae to Pseudosimochromis was justified by the similarity of their Cichlidogyrus fauna and the intermediate morphology of S. margaretae. Finally parasite data also supported the synonymy between S. pleurospilus and S. babaulti, a species that contains a large amount of geographical morphological variation.

Background: Adaptation to different ecological environments is thought to drive ecological speciation. This phenomenon culminates in the radiations of cichlid fishes in the African Great Lakes. Multiple characteristic traits of cichlids, targeted by natural or sexual selection, are considered among the driving factors of these radiations. Parasites and pathogens have been suggested to initiate or accelerate speciation by triggering both natural and sexual selection. Three prerequisites for parasite-driven speciation can be inferred from ecological speciation theory. The first prerequisite is that different populations experience divergent infection levels. The second prerequisite is that these infection levels cause divergent selection and facilitate adaptive divergence. The third prerequisite is that parasite-driven adaptive divergence facilitates the evolution of reproductive isolation. Here we investigate the first and the second prerequisite in allopatric chromatically differentiated lineages of the rock-dwelling cichlid Tropheus spp. from southern Lake Tanganyika (Central Africa). Macroparasite communities were screened in eight populations belonging to five different colour morphs., Results: Parasite communities were mainly composed of acanthocephalans, nematodes, monogeneans, copepods, branchiurans, and digeneans. In two consecutive years (2011 and 2012), we observed significant variation across populations for infection with acanthocephalans, nematodes, monogeneans of the genera Gyrodactylus and Cichlidogyrus, and the copepod Ergasilus spp. Overall, parasite community composition differed significantly between populations of different colour morphs. Differences in parasite community composition were stable in time. The genetic structure of Tropheus populations was strong and showed a significant isolation-by-distance pattern, confirming that spatial isolation is limiting host dispersal. Correlations between parasite community composition and Tropheus genetic differentiation were not significant, suggesting that host dispersal does not influence parasite community diversification., Conclusions: Subject to alternating episodes of isolation and secondary contact because of lake level fluctuations, Tropheus colour morphs are believed to accumulate and maintain genetic differentiation through a combination of vicariance, philopatric behaviour and mate discrimination. Provided that the observed contrasts in parasitism facilitate adaptive divergence among populations in allopatry (which is the current situation), and promote the evolution of reproductive isolation during episodes of sympatry, parasites might facilitate speciation in this genus.

Fishes normally restricted to inland waters are valuable model systems for historical biogeography, inter alia, because of their limited dispersal abilities and concordance with the distribution patterns of other freshwater taxa (Zogaris et al. 2009). The comparison of fish species assemblages has been the major biogeographical tool for delineating African aquatic ecoregions as the fossil record is often meagre and merely offers complementary information. This is, for example, the case for the Zambezian and Congolian ichthyofaunal provinces, which display substantial contemporary fish diversity (Stewart 2001). Between both regions lies the Bangweulu-Mweru ecoregion (sensu Scott 2005), known for its high percentage of endemicity. Although hydrographically belonging to the Congo Basin, the Bangweulu-Mweru ecoregion has a high affinity with the Zambezi province (Scott 2005), due to historical river connections (Tweddle 2010). Studies comparing the Zambezi and Congo ichthyofaunal provinces are rare and hampered by lack of data from the Congo Basin. The latter harbours more than 1250 fish species (Snoeks et al. 2011) while in the Zambezi, only 120 freshwater fishes are found (Tweddle 2010). Indeed, species richness declines in all major African teleost families from the Congo Basin southwards, riverine haplochromine cichlids forming a notable exception to this rule (Joyce et al. 2005). Although it was hypothesized by Tweddle (2010) that the origin of many Zambezian fish species is in the Congo Basin, the haplochromines Serranochromis Regan, Sargochromis Regan, Pharyngochromis Greenwood and Chetia Trewavas, together forming the serranochromines, have their centre of diversity in the rivers of the Zambezian ichthyofaunal province (Joyce et al. 2005). Therefore, the biogeographical history of Cichlidae across the Zambezi- Congo watershed is not only key to cichlid biogeography on an African scale, but also complementary to biogeography of all other teleosts in the region. Yet, colonisation and speciation patterns are difficult to unravel due to complex hydrological history (Katongo et al. 2007; Schwarzer et al. 2012).

The megadiverse haplochromine cichlid radiations of the East African lakes, famous examples of explosive speciation and adaptive radiation, are according to recent studies, introgressed by different riverine lineages. This study is based on the first comprehensive mitochondrial and nuclear DNA dataset from extensive sampling of riverine haplochromine cichlids. It includes species from the lower River Congo and Angolan (River Kwanza) drainages. Reconstruction of phylogenetic hypotheses revealed the paradox of clearly discordant phylogenetic signals. Closely related mtDNA haplotypes are distributed thousands of kilometres apart and across major African watersheds, whereas some neighbouring species carry drastically divergent mtDNA haplotypes. At shallow and deep phylogenetic layers, strong signals of hybridization are attributed to the complex Late Miocene/Early Pliocene palaeohistory of African rivers. Hybridization of multiple lineages across changing watersheds shaped each of the major haplochromine radiations in lakes Tanganyika, Victoria, Malawi and the Kalahari Palaeolakes, as well as a miniature species flock in the Congo basin (River Fwa). On the basis of our results, introgression occurred not only on a spatially restricted scale, but massively over almost the whole range of the haplochromine distribution. This provides an alternative view on the origin and exceptional high diversity of this enigmatic vertebrate group.

Lake Tanganyika harbours the most diverse endemic cichlid fish assemblage of Africa, but its monogenean fish parasites have not been investigated. Here we report, for the first time, on the Gyrodactylus parasites in this hotspot of fish biodiversity. Haptor morphometrics and nuclear ribosomal DNA sequences revealed 3 new species on Zambian Simochromis diagramma: Gyrodactylus sturmbaueri n. sp., G. thysi n. sp. and G. zimbae n. sp. Their distinct morphology and strong genetic differentiation suggest that they belong to distant lineages within the genus Gyrodactylus, and phylogenetic reconstructions suggest affinities with other genera of gyrodactylids. Additional U-shaped haptoral plates in G. thysi n. sp. and a second large spine-like structure in the male copulatory organ of G. zimbae seem to represent new features for the genus. Such large diversity on a single host species can probably be explained by host-switching events during the course of evolution, in agreement with the generally accepted concept that ecological transfer is an important aspect of gyrodactylid speciation. Additional parasitological surveys on other host species, covering a broader phylogenetic and geographical range, should clarify the evolutionary history of Gyrodactylidae on cichlids in the African Great Lake and other parts of Africa.

Background: Deterministic evolution, phylogenetic contingency and evolutionary chance each can influence patterns of morphological diversification during adaptive radiation. In comparative studies of replicate radiations, convergence in a common morphospace implicates determinism, whereas non-convergence suggests the importance of contingency or chance., Methodology/principal Findings: The endemic cichlid fish assemblages of the three African great lakes have evolved similar sets of ecomorphs but show evidence of non-convergence when compared in a common morphospace, suggesting the importance of contingency and/or chance. We then analyzed the morphological diversity of each assemblage independently and compared their axes of diversification in the unconstrained global morphospace. We find that despite differences in phylogenetic composition, invasion history, and ecological setting, the three assemblages are diversifying along parallel axes through morphospace and have nearly identical variance-covariance structures among morphological elements., Conclusions/significance: By demonstrating that replicate adaptive radiations are diverging along parallel axes, we have shown that non-convergence in the common morphospace is associated with convergence in the global morphospace. Applying these complimentary analyses to future comparative studies will improve our understanding of the relationship between morphological convergence and non-convergence, and the roles of contingency, chance and determinism in driving morphological diversification.

The species flocks of cichlid fishes in the East African Lakes Tanganyika, Malawi and Victoria are prime examples of adaptive radiation and explosive speciation. Several hundreds of endemic species have evolved in each of the lakes over the past several thousands to a few millions years. Sexual selection via colour-assortative mating has often been proposed as a probable causal factor for initiating and maintaining reproductive isolation. Here, we report the consequences of human-mediated admixis among differentially coloured populations of the endemic cichlid fish Tropheus moorii from several localities that have accidentally been put in sympatry in a small harbour bay in the very south of Lake Tanganyika. We analysed the phenotypes (coloration) and genotypes (mitochondrial control region and five microsatellite loci) of almost 500 individuals, sampled over 3 consecutive years. Maximum-likelihood-based parenthood analyses and Bayesian inference of population structure revealed that significantly more juveniles are the product of within-colour-morph matings than could be expected under the assumption of random mating. Our results clearly indicate a marked degree of assortative mating with respect to the different colour morphs. Therefore, we postulate that sexual selection based on social interactions and female mate choice has played an important role in the formation and maintenance of the different colour morphs in Tropheus, and is probably common in other maternally mouthbrooding cichlids as well.

Lake Victoria harbors a unique species-rich flock of more than 500 endemic haplochromine cichlid fishes. The origin, age, and mechanism of diversification of this extraordinary radiation are still debated. Geological evidence suggests that the lake dried out completely about 14,700 years ago. On the basis of phylogenetic analyses of almost 300 DNA sequences of the mitochondrial control region of East African cichlids, we find that the Lake Victoria cichlid flock is derived from the geologically older Lake Kivu. We suggest that the two seeding lineages may have already been lake-adapted when they colonized Lake Victoria. A haplotype analysis further shows that the most recent desiccation of Lake Victoria did not lead to a complete extinction of its endemic cichlid fauna and that the major lineage diversification took place about 100,000 years ago.

The East African Great Lakes are inhabited by impressive radiations of cichlids that display a large variation in morphology, diet, colour pattern, and behaviour and have adapted to a large array of niches. Whilst most of these cichlids are bottom dwellers, a number of species have adapted to a pelagic environment and inhabit open waters. From the Lake Edward system, one pelagic species had been previously described, the zooplanktivorous Haplochromis pappenheimi. Our sampling revealed the Lake Edward system to be inhabited by two more pelagic species that were unknown to science and are formally described here, the zooplanktivorous Haplochromis pelagicus sp. nov. and the insectivorous H. aureus sp. nov. All three species seem mostly restricted to deepwater regions where the depth exceeds six metres in Lake Edward, except for H. pelagicus sp. nov., which also occurs in shallower regions of Lakes Edward and George and of the Kazinga Channel. Sexual dimorphism, mainly in head shape, was discovered in H. pappenheimi and H. pelagicus sp. nov. These differences suggest that females of these species have larger buccal cavities than males, which is most likely linked to female mouth brooding behaviour. [ABSTRACT FROM AUTHOR]

Nile tilapia, one of the most popular aquaculture species worldwide, has been introduced into the Congo Basin several times for aquaculture purposes. Previous studies based on morphological features showed that some of the monogenean gill parasites were co-introduced with Nile tilapia and some spilled over to native Congolese cichlids. In this study, we genetically investigated the co-introduced monogeneans of Nile tilapia from three major parts of the Congo Basin: Upper, Middle and Lower Congo. We sequenced 214 specimens belonging to 16 species of Monogenea, collected from native and introduced tilapia species from Congo, Madagascar and Burundi. We evaluate their position in a phylogeny including 38 monogenean species in total. Our results confirm the co-introductions in the Congo Basin and suggest one unreported parasite transmission from introduced Nile tilapia to native Mweru tilapia in Upper Congo, which was undetectable with a morphological study alone. Shared parasite COI haplotypes between Madagascar and the Congo Basin illustrate how anthropogenic introduction events homogenize parasite communities across large geographical distances and thereby disrupt isolation by distance patterns. Contrary to our expectation, the parasite populations co-introduced in the Congo Basin reveal a high COI diversity, probably resulting from multiple Nile tilapia introductions from different geographic origins. Additionally, we tested the barcoding gap and the performance of mitochondrial COI and nuclear ribosomal ITS-1, 28S and 18S markers. We found a significant barcoding gap of 15% for COI, but none for the other markers. Our molecular results reveal that Cichlidogyrus halli, C. papernastrema, C. tiberianus, C. cirratus and C. zambezensis are in need of taxonomic revision. [ABSTRACT FROM AUTHOR]

The group of large five-spotted Hemichromis species from West Africa and Lower Guinea was revised using an integrative approach combining morphometry (measurements, meristics and colour patterns) and genetics (cytochrome b gene). Specimens from 100 populations were sorted into three main groups on the basis of morphological criteria. Samples from Lake Bosumtwi clustered together with others from West Africa in a large well-supported clade (bootstrap values and posterior probabilities: 98/96/100), both in morphometric and genetic analyses, raising again the hypothesis of synonymy of H. frempongi with H. fasciatus. Samples from southern Lower Guinea, including the type locality (Gabon) of H. elongatus, constituted a second weakly resolved cluster (64/38/51), resulting from a potential admixture of populations of diverse origins which share common morphological traits. Populations from northern Lower Guinea (Atlantic coastal basins) and the upper Chad basin in Cameroon formed a third strongly supported clade (99/100/100), which corresponds to a new species, Hemichromis camerounensis sp. nov., herein described. [ABSTRACT FROM AUTHOR]

The Lake Edward system in Eastern Central Africa, including Lakes Edward and George and their associated rivers, is home to a species assemblage of endemic haplochromine cichlids. Currently, 36 of these species have been formally described, while it is estimated that the system may harbour a total of 60 species. Species flocks of haplochromine cichlids are morphologically and ecologically very diverse and have radiated into many specialised trophic niches. Paedophagy is the feeding on eggs and larvae. In Haplochromis, most paedophages steal fry and eggs from the buccal cavities of mouthbrooding female cichlids. Hitherto, one formally described species with this diet is known from the Lake Edward system: Haplochromis taurinus. We performed a morphometrical revision of all species of Haplochromis from this system with a morphology that suggests a paedophagous diet: long oral jaws set with small teeth. Sixty-eight specimens were studied by taking 28 measurements and 20 counts and by performing stomach content observations. We discovered that H. paradoxus also had a paedophagous diet. Our analyses further revealed the presence of three new species: H. gracilifur sp. nov., H. molossus sp. nov., and H. relictidens sp. nov. All five of these species were described or redescribed. [ABSTRACT FROM AUTHOR]

A new species of Trematocranus, T. pachychilus sp. n., is described from Lake Malawi. So far, it has only been found at Jafua Bay, Mozambique. It can easily be distinguished from T. labifer by its molariform pharyngeal dentition. A morphometric study, including 24 measurements and 15 counts, was done to compare the new species with T. microstoma and T. placodon. Trematocranus pachychilus is characterised by its thick lips. This species further differs from T. microstoma by its bicuspid (vs. unicuspid) outer oral teeth, wide (vs. small) pharyngeal bone, and its head shape. It resembles T. placodon, from which it can be distinguished by its straight to concave head profile (vs. rounded), less-developed pharyngeal bones (vs. hypertrophied), and the presence of small to minute teeth on the lateral parts of the dentigerous area on the lower pharyngeal bone. A key to the species of Trematocranus is provided. [ABSTRACT FROM AUTHOR]

Intra-specific morphological variation in the cichlid Tropheus duboisi from 10 localities over its entire known distribution area along the central eastern and northern shore of Lake Tanganyika was investigated. This revealed significant differences between various populations that are geographically isolated. These morphological observations only partially correspond to the results of a haplotype network, based on mtDNA. In addition, a difference in the timing of the onset of the adult colour pattern was discovered for one isolated population. The occurrence of morphological intra-specific differentiation is discussed with respect to the basal position of T. duboisi within Tropheus as well as to the presumed morphological stasis of the genus. [ABSTRACT FROM AUTHOR]

The megadiverse haplochromine cichlid radiations of the East African lakes, famous examples of explosive speciation and adaptive radiation, are according to recent studies, introgressed by different riverine lineages. This study is based on the first comprehensive mitochondrial and nuclear DNA dataset from extensive sampling of riverine haplochromine cichlids. It includes species from the lower River Congo and Angolan (River Kwanza) drainages. Reconstruction of phylogenetic hypotheses revealed the paradox of clearly discordant phylogenetic signals. Closely related mtDNA haplotypes are distributed thousands of kilometres apart and across major African watersheds, whereas some neighbouring species carry drastically divergent mtDNA haplotypes. At shallow and deep phylogenetic layers, strong signals of hybridization are attributed to the complex Late Miocene/Early Pliocene palaeohistory of African rivers. Hybridization of multiple lineages across changing watersheds shaped each of the major haplochromine radiations in lakes Tanganyika, Victoria, Malawi and the Kalahari Palaeolakes, as well as a miniature species flock in the Congo basin (River Fwa). On the basis of our results, introgression occurred not only on a spatially restricted scale, but massively over almost the whole range of the haplochromine distribution. This provides an alternative view on the origin and exceptional high diversity of this enigmatic vertebrate group. [ABSTRACT FROM AUTHOR]

We present a comprehensive phylogenetic analysis of the Utaka, an informal taxonomic group of cichlid species fromLakeMalawi. We analyse both nuclear and mtDNA data from five Utaka species representing two (Copadichromis and Mchenga) of the three genera within Utaka. Within three of the five analysed species we find two very divergent mtDNA lineages. These lineages are widespread and occur sympatrically in conspecific individuals in different areas throughout the lake. In a broader taxonomic context including representatives of the main groups within the Lake Malawi cichlid fauna, we find that one of these lineages clusters within the non-Mbuna mtDNA clade, while the other forms a separate clade stemming from the base of the Malawian cichlid radiation. This second mtDNA lineage was only found in Utaka individuals, mostly within Copadichromis sp. "virginalis kajose" specimens. The nuclear genes analysed, on the other hand, did not show traces of divergence within each species. We suggest that the discrepancy between the mtDNA and the nuclear DNA signatures is best explained by a past hybridisation event by which the mtDNA of another species introgressed into the ancestral Copadichromis sp. "virginalis kajose" gene pool. [ABSTRACT FROM AUTHOR]

Peripheral isolated populationsmay undergo rapid divergence from themain population due to various factors such as a bottleneck or a founder effect followed by genetic drift or local selection pressures. Recent populations of two economically important Copadichromis species in Lake Malombe, a satellite lake of Lake Malawi, were neither genetically nor morphometrically distinct from their source populations in themain lake. Evidence was found for a founder effect which had a different impact on the genetic composition of the two species. In addition, the increased fishing pressure in Lake Malombe may have led to a reduction of the body sizes of both species. [ABSTRACT FROM AUTHOR]

We discuss geographical distribution and phylogeny of Dactylogyridea (Monogenea) parasitizing Cichlidae to elucidate their hosts' history. Although mesoparasitic Monogenea (Enterogyrus spp.) show typical vicariant distribution, ectoparasitic representatives from different continents are not considered sister taxa, hence their distribution cannot result from vicariance alone. Because of the close host-parasite relationship, this might indicate that present-day cichlid distribution may also reflect dispersal through coastal or brackish waters. Loss of ectoparasites during transoceanic migration, followed by lateral transfer from other fish families might explain extant host-parasite associations. Because of its mesoparasitic nature, hence not subject to salinity variations of the host's environment, Enterogyrus could have survived marine migrations, intolerable for ectoparasites. Host-switches and salinity transitions may be invoked to explain the pattern revealed by a preliminary morphological phylogeny of monogenean genera from Cichlidae and other selected Monogenea genera, rendering the parasite distribution explicable under both vicariance and dispersal. Testable hypotheses are put forward in this parasitological approach to cichlid biogeography. Along with more comprehensive in depth morphological phylogeny, comparison with molecular data, clarifying dactylogyridean evolution on different continents and from various fish families, and providing temporal information on host-parasite history, are needed to discriminate between the possible scenarios. [ABSTRACT FROM AUTHOR]

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Background: Species delineation is particularly challenging in taxa with substantial intra-specific variation. In systematic studies of fishes, meristics and linear measurements that describe shape are often used to delineate species. Yet, little is known about the taxonomic value of these two types of morphological characteristics. Here, we used Tropheus (Teleostei, Cichlidae) from the southern subbasin of Lake Tanganyika to test which of these types of characters best matched genetic lineages that could represent species in this group of stenotypic rock-dwelling cichlids. We further investigated intra-population variation in morphology. By linking this to a proxy of a population's age, we could assess the evolutionary stability of different kinds of morphological markers. Results: Morphological data was collected from 570 specimens originating from 86 localities. An AFLP approach revealed the presence of five lineages in the southern subbasin: T. moorii, T. brichardi, T. sp. 'maculatus', T. sp. 'Mpimbwe' and T. sp. 'red', which we consider to represent distinct species. Although both types of morphological data supported this classification, a comparison of PST-values that describe inter-population morphological differentiation, revealed a better correspondence between the taxon delineation based on AFLP data and the patterns revealed by an analysis of meristics than between the AFLP-based taxon delineation and the patterns revealed by an analysis of shape. However, classifying southern populations of Tropheus was inherently difficult as they contained a large amount of clinal variation, both in genetic and in morphological data, and both within and among species. A scenario is put forward to explain the current-day distribution of the species and colour varieties and the observed clinal variation across the subbasin's shoreline. Additionally, we observed that variation in shape was larger in populations from shallow shores whereas populations from steep shores were more variable in meristics. This difference is explained in terms of the different timescales at which small and large scale lake level fluctuations affected populations of littoral cichlids at steep and shallow shores. Conclusions: Our results showed meristics to be more evolutionary stable, and of higher taxonomic value for species delimitation in Tropheus, than linear measurements that describe shape. These results should be taken into account when interpreting morphological differences between populations of highly stenotypic species, such as littoral cichlids from the Great East African Lakes. [ABSTRACT FROM AUTHOR]