African Freshwater Fish Research Articles

Comparative lipid composition and GC–MS fatty acid profiling of tropical African freshwater fishes

In dietary contexts, fish are renowned for the diverse array of unsaturated fatty acids they provide to the body. While data regarding the fatty acid composition of freshwater fish are readily available in most developed countries, research on African freshwater fish remains notably limited. In this study, we investigated the fatty acid composition of fifteen freshwater fish species from Africa, primarily Afrotropical regions. Lipids were extracted using a solvent mixture of methanol, water, and chloroform. Subsequently, total fatty acids were determined by saponification, and the fatty acid profile was analyzed via GC–MS following methylation in the presence of BF3 and methanol. The results revealed lipid levels in fish fillets ranging from 1.99 % for T. guineensis to 6.41 % for M. bananensis. Total fatty acid percentages of lipids were found to be 81.40 ± 9.15 % for S. nigripinnis, 83.75 ± 6.12 % for L. niloticus, and 92.99 ± 11.30 % for C. dageti. The fatty acid profiles of 15 properly identified fish species have been determined, with the majority being identified for the first time. The composition of health-important omega-3 fatty acids EPA and total DHA ranged from 4.82 ± 0.2 % for Cyprinus lepidotus to 17.43 ± 2.50 % for Mugil bananensis. Unsupervised multivariate data analysis of fatty acid profiles of the different fish species showed significant differences. When the fish were grouped into 4 categories based on their similarities, 12 discriminant fatty acids characteristic of each group were identified. Among these fatty acids are omega-6 acids such as γ-linolenic acid and arachidonic acid, and omega-3 7,10,13,16,19-docosapentaenoic acid (DPA). This research opens avenues for consumers to make informed dietary choices aligned with their specific fatty acid needs and preferences regarding fish consumption.

The status of COI and 12S rRNA DNA barcode reference libraries for freshwater fish in South Africa: Implications for future eDNA projects

Environmental DNA metabarcoding (eDNA) is a rapidly emerging field in which high-throughput sequencing is used to catalogue the biodiversity of ecosystems through the amplification of DNA extracted from environmental samples (water, air, faeces and soil). Although eDNA has strong links to DNA barcoding, the molecular marker most often used to detect vertebrates in eDNA studies is a portion of the mitochondrial 12S ribosomal RNA (12S rRNA) and not the standard cytochrome oxidase I (COI) marker used in traditional DNA barcoding. eDNA methods rely on a comprehensive reference library to link sequence data to species, which are often lacking in hyper-diverse countries such as South Africa. In this study, we review the present state of DNA barcode reference databases for both 12S rRNA and COI for freshwater fish (native and introduced) found in South African aquatic systems. Analysis of DNA records available on GenBank and the Barcode of Life Database (BOLD) revealed incomplete records of the examined taxa for both markers. Our findings showed that 34 species, 6 genera and 0 families of native South African freshwater fish lack COI barcode records, while 86 species, 22 genera and 8 families lack 12S rRNA records. Unlike the native freshwater fish, the non-native fish all had barcode records available for both COI and 12S rRNA. Producing comprehensive reference libraries for both markers is an important first step in developing an eDNA protocol for the non-invasive monitoring of native and non-native freshwater fish in South Africa.

From Africa to the world—The journey of Nile tilapia

AbstractDespite the fact that Nile tilapia (Oreochromis niloticus) (Linnaeus, 1758) are African freshwater fish, they have been introduced into many countries inside and outside Africa. The journey of Nile tilapia started during the second half of the 20th Century, especially in Southeast Asia and the Americas, mainly for aquaculture and fisheries enhancement. Most of these introductions became well established in aquaculture. As a result, aquaculture of Nile tilapia has been steadily expanding in many countries. These fish play an important role in the livelihoods of local societies on different continents. This review summarizes the current knowledge on global Nile tilapia introductions and sheds light on their social and economic contributions to the countries into which they have been introduced, as well as their share in the global fish market. The ecological impacts of tilapia introductions have also been addressed. The success stories of the major Nile tilapia producers were highlighted so that the lessons learned from their experiences could be transferred to other countries.

Two new species of Cephalogonimidae Looss, 1899 (Digenea: Plagiorchioidea) from Africa (Mozambique and Guinea), including a new phylogenetic hypothesis for related plagiorchioids.

Two new species of Cephalogonimidae Looss, 1899 (from Emoleptalea Looss, 1900 and Masenia Chatterji, 1933) are described from African freshwater fishes. Emoleptalea mozambiquensis n. sp. infected the turquoise killifish, Nothobranchius furzeri Jubb, in Mozambique and differs from its nine congeners by the combination of differences in body shape and size, oral sucker shape, sucker width ratio, configuration of the digestive tract and gonads, vitelline follicle shape and vitellarium configuration. Emoleptalea dollfusi Srivastava, 1960 is a synonym of Emoleptalea loossi Srivastava, 1960, thus there are still nine accepted species. Masenia baroensis n. sp. infected the globe fish, Tetraodon lineatus L., in the Republic of Guinea and differs from its five African congeners and 15 Asian congeners by the combination of circumoral spine count, oral sucker shape, caecal extent, ovary shape, genital pore position, and configuration of the vitellarium. Masenia dayali (Gupta & Puri, 1984) Chandra & Saxena, 2016 and Masenia pushpanjalii are nomina dubia. We propose Masenia ritai (Agrawal, 1964) n. comb., with M. ritai Sircar & Sinha, 1970 its junior synonym. Heterorchis cf. crumenifer (identified tentatively due to egg size) is reported from the West African lungfish, Protopterus annectens (Owen), in Mozambique (new geographical record). Heterorchis protopteri Thomas, 1958 and Heterorchis ghanensis Thomas, 1968 are species inquirendae. Sequences (28S rDNA) from these parasites were included in a Bayesian phylogenetic analysis with 37 other ingroup taxa. Both new species formed a clade with Masenia nkomatiensis Dumbo, Dos Santos & Avenant-Oldewage, 2019 from Africa. These three species formed a sister relationship with the other available cephalogonimids: Cephalogonimus americanus Stafford, 1902 and Cephalogonimus retusus (Dujardin, 1845), both frog parasites from North America and Europe, respectively. Heterorchis cf. crumenifer represented a distinct lineage within the Plagiorchioidea but formed a polytomy with species from 10 plagiorchioid families.

Morphological and molecular characterization of an African freshwater fish trypanosome, including its development in a leech vector

Trypanosomes are ubiquitous blood parasites of fishes and at least 16 species were originally described infecting African freshwater fishes. This number was later reduced to six and in the late 1990s it was proposed that most records of freshwater fish trypanosomes across Africa are Trypanosoma mukasai Hoare, 1932. Recently, results from a molecular analysis of fish trypanosomes from the Okavango Delta, Botswana, reported the presence of at least two genotypic groups and concluded that the identification of T. mukasai remains problematic. The aims of the present study were thus to elucidate the life cycle of a freshwater fish trypanosome from southern Africa and to do a morphological and molecular characterization of this parasite from both the fish host and leech vector. To locate trypanosome stages, leeches were removed from fishes captured in the Phongolo River, South Africa, and fish blood films and leech squashes were Giemsa-stained and screened. To determine whether trypanosome stages in fishes and leeches were of the same genotype, DNA was extracted and fragments of the 18S rDNA gene were amplified and sequenced. Trypanosomes were detected in the fish families Cichlidae, Clariidae, Mochokidae and Schilbeidae. Sequence data showed that the trypanosome from one of the leeches, identified as Batracobdelloides tricarinata (Blanchard, 1897), was highly similar to those obtained from the plain squeaker, Synodontis zambezensis, with 0.7% difference recorded between them. From morphological and molecular data presented here, it is clear that the trypanosomes from Phongolo are closely related to those of the Okavango and should be considered as a single diverse species with genetic differentiation between 0.4–2.9%, under the 3–5% differences expected to be seen between true distinct species within the rRNA. Developmental stages of the trypanosome found in the leech B. tricarinata supports its status as the vector and the molecular evidence shows the relationship between the trypanosome in the fish and leech, but also illustrates the exceptional genetic and morphological diversity of a single species of trypanosome between host species. The work presented here provides us with clear information to take further steps in resolving the taxonomy and systematics of African freshwater fish trypanosomes.

Pattern and timing of diversification in the African freshwater fish genus Distichodus (Characiformes: Distichodontidae)

BackgroundDistichodus is a clade of tropical freshwater fishes currently comprising 25 named species distributed continent-wide throughout the Nilo-Sudan and most Sub-Saharan drainages. This study investigates the phylogenetic relationships, timing of diversification, and biogeographic history of the genus from a taxonomically comprehensive mutilocus dataset analyzed using Maximum Likelihood and Bayesian methods of phylogenetic inference, coalescence-based species-tree estimation, divergence time estimation, and inference of geographic range evolution.ResultsAnalyses of comparative DNA sequence data in a phylogenetic context reveal the existence of two major clades of similar species-level diversity and provide support for the monophyletic status of most sampled species. Biogeographic reconstruction on a time-scaled phylogeny suggest that the origins of the genus date back to the late Oligocene and that current geographic distributions are the result of a Congo Basin origin followed by dispersal and range expansion into adjacent ichthyofaunal provinces at different times during the evolutionary history of the group.ConclusionsWe present the most comprehensive phylogenetic, chronological, and biogeographic treatment yet conducted for the genus. The few instances of species paraphyly (D. teugelsi, D. fasciolatus) revealed by the resulting phylogenies are likely a consequence of post-divergence introgressive hybridization and/or incomplete lineage sorting due to recent speciation. Historical biogeographic findings are both in agreement and conflict with previous studies of other continent-wide African freshwater fish genera, suggesting a complex scenario for the assemblage of Africa’s continental ichthyofaunal communities.

Unravelling the evolution of Africa’s drainage basins through a widespread freshwater fish, the African sharptooth catfish Clarias gariepinus

AbstractAimThe formation history of Africa's current river basins remains largely unknown. In order to date changes in landscape and climate, we studied the biogeography of the African freshwater fish with the largest natural distribution. We also validated biogeographical units.LocationContinental Africa.TaxonClarias gariepinus sl.MethodsWe investigated mitochondrial cytb sequences of 443 individuals from 97 localities, using a haplotype network and a genetic landscape analysis. We inferred a dated phylogeny using maximum likelihood and Bayesian inference approaches and reconstructed ancestral areas with S‐DEC and S‐DIVA models. Microsatellite genotyping complemented the mitochondrial approach in the Congo basin, where the latter revealed complex patterns.ResultsLimited differentiation is found in northern and south‐western Africa, and sharp genetic differentiation in the continent's east and centre. Populations with affinities to neighbouring basins occur at the edges of the Congo province. High diversity exists in the south of the Congo basin. The Zambezi province is partitioned into eastern, central and western sectors. In the east, specimens were related to those from the Congo. In the west, they were similar to Southern representatives. Phylogenetic inference placed the origin of C. gariepinus in the East Coast, with intraspecific diversification starting around the Great Lakes. These events occurred ca. 4.8–1.65 and 2.3–0.8 MYA respectively.Main conclusionsClades of C. gariepinus sl. show a clear geographical signature. The origin of C. gariepinus in the East Coast and diversification around the Great Lakes coincided with the periods of increased aridity. Low genetic differentiation in northern and southern Africa may result from connectivity during recent periods of higher rainfall. In contrast to other widespread African freshwater fish, colonization rather than extinction seemed to mediate distribution patterns. This can be explained by a high ecological tolerance. We highlight the species’ suitability to study landscape and climate evolution at various scales.

First empirical study of freshwater microplastics in West Africa using gastropods from Nigeria as bioindicators

Freshwater environments are the route through which inland plastics are transported to the ocean, explaining why the number of freshwater microplastic (MP) studies has recently been increasing. Despite the lack of recycling and the presence of severe plastic pollution in many African countries, MPs have been scarcely reported in African freshwaters and the current study gives the first empirical account for West Africa. The study investigates MP pollution in an important West African river system (Osun River system, Nigeria) and gives an insight into microplastic contamination in a main European river (Rhine River), using gastropods which are potential consumers of MPs, from both systems. From the Osun River system, the most common gastropods (Lanistes varicus and Melanoides tuberculata) were analysed for MP contamination. Two MP types (fibre and film) were recorded in L. varicus, whereas only fibre was recorded in M. tuberculata. Micro-Fourier-transform infrared spectroscopy (μFTIR) revealed that the MP films in the African gastropods were made of polyethylene and strongly resembled black polyethylene bags that covered the Osun River banks. From the Rhine River, the gastropod Theodoxus fluviatilis was analysed and nylon as well as polypropylene fibres were found. In both systems (Osun River and Rhine River), fibre was the dominant MP type. In conclusion, the study shows that MP contamination in Nigeria, a West African country with a lack of recycling and poor waste management practice, is reflected in two different local gastropod species. Furthermore, the comparison with a European gastropod species shows that fibres are the dominant MP type in gastropods from both freshwater systems. In both systems, MPs ingested by the gastropods could be transferred to higher trophic levels following predation. We therefore recommend that more empirical studies should be carried out along different feeding guilds of African freshwater invertebrates and fish. When MPs are transferred to fish, MPs may reach humans through fish consumption.

Assessing the vulnerability of Africa's freshwater fishes to climate change: A continent-wide trait-based analysis

Climate change is a key driver of biodiversity loss across the globe, and freshwater fishes are predicted to be among the most vulnerable taxa. African freshwater ecosystems are home to one of the most unique and diverse ichthyo-faunas on the planet, and freshwater fish species provide essential livelihoods for millions of people living in riparian communities across the continent. Although nearly one sixth of African freshwater fishes have been designated as endangered or vulnerable to extinction by the IUCN Red List assessment, the effects of climate change on these species have not been explored on a continent-wide scale. In this study, we present the first trait-based climate change vulnerability assessment (CCVA) comprising the majority (85%) of Africa's currently described freshwater fishes. We assembled data relating to three dimensions of vulnerability including sensitivity, adaptive capacity, and exposure. In addition, we developed an index of ‘conservation value’ based on traditional conservation metrics including extinction risk, endemism, and provision of ecosystem services. We found that almost 40% of African freshwater fishes are vulnerable to climate change, mostly owing to the many species with highly specialized habitat and life-history requirements, and because of the numerous anthropogenic stressors they face. High proportions of species within the Nothobranchiidae and Cichlidae families were found to be vulnerable. Regions with high frequencies of vulnerable species included the African rift valley lakes, the Congo River drainage, and the coastal rivers of West Africa. Several important data deficiencies were identified relating to species' population sizes, genetic variability, and life history traits, and constitute priority research areas for the future. In addition, we highlighted some cases where traditional conservation approaches overlook species and regions that are predicted to be threatened by climate change.

Temperature preference of Nile tilapia (Oreochromis niloticus) juveniles induces spontaneous sex reversal.

Nile tilapia (Oreochromis niloticus) is an African freshwater fish that displays a genetic sex determination system (XX|XY) where high temperatures (above 32°C to 36.5°C) induce masculinization. In Nile tilapia, the thermosensitive period was reported from 10 to 30 days post fertilization. In their natural environment, juveniles may encounter high temperatures that are above the optimal temperature for growth (27–30°C). The relevance of the thermal sex reversal mechanism in a natural context remains unclear. The main objective of our study is to determine whether sexually undifferentiated juveniles spontaneously prefer higher, unfavorable temperatures and whether this choice skews the sex ratio toward males. Five full-sib progenies (from 100% XX crosses) were subjected to (1) a horizontal three-compartment thermal step gradient (thermal continuum 28°C– 32°C– 36.5°C) during the thermosensitive period, (2) a control continuum (28°C– 28°C– 28°C) and (3) a thermal control tank (36.5°C). During the first days of the treatment, up to an average of 20% of the population preferred the masculinizing compartment of the thermal continuum (36.5°C) compared to the control continuum. During the second part of the treatment, juveniles preferred the lower, nonmasculinizing 32°C temperature. This short exposure to higher temperatures was sufficient to significantly skew the sex ratio toward males, compared to congeners raised at 28°C (from 5.0 ± 6.7% to 15.6 ± 16.5% of males). The proportion of males was significantly different in the thermal continuum, thermal control tank and control continuum, and it was positively correlated among populations. Our study shows for the first time that Nile tilapia juveniles can choose a masculinizing temperature during a short period of time. This preference is sufficient to induce sex reversal to males within a population. For the first time, behavior is reported as a potential player in the sex determination mechanism of this species.

Fatty acids composition in South African freshwater fish as indicators of food quality

Lipid classes and fatty acid composition of three commercially important freshwater fish species Oreochromis mossambicus (Mozambique tilapia), Clarias gariepinus (African catfish) and Cyprinus carpio (carp) obtained from an aquaculture, different river systems and fish markets from different provinces in South Africa were investigated. Fatty acids were extracted from the fish fillets through the Folch extraction method (using chloroform: methanol at the ratio of 2:1). Generally, tilapia fish species was found to be the richest in fatty acid composition. In all fish species analysed, palmitic acid (16:0) was found to be the most abundant fatty acid ranging from 18.24 to 21.84%. Appreciable quantities of essential polyunsaturated fatty acid such as docosahexaenoic (DHA) (22:6 n-3, 3.92 to 6.16%), eicosapentaenoic acid (EPA) (20:5 n-3, 1.91 to 2.92%) and arachidonic acid (20:4 n-6, 7.19 to 8.50%) were also found. Observations show that fish species obtained from Gauteng Province are richer in fatty acids compared to those in Limpopo Province. The study points out that all fish species investigated contain appreciable levels of Omega-3 (n-3) polyunsaturated fatty acids (PUFA) and are therefore suitable for an unsaturated low-fat diet. This is important especially for poor communities who cannot afford to get a balanced diet, rich in some essential fatty acids.Therefore, it is important to determine the nutritional value of local fish, since it significantly contribute to a healthy diet in rural communities.

Journal of Fish Biology Special Issue on Biology and Ecology of African Freshwater Fishes

Journal of Fish Biology Special Issue on Biology and Ecology of African Freshwater Fishes

The first report of two monogenean gill parasites assigned to ‎Diclidophora merlangi (Diclidophoridae) and Loxuroides pricei ‎‎(Axinidae) from brushtooth lizardfish and red porgy seabream of ‎the Red Sea, Egypt.

Monogenea is one of the most species-rich groups of parasitic flatworms worldwide with many species described from African freshwater fish. Little is known about the diversity and geographic distribution of monogenean parasites infesting the Red Sea fishes in Egypt. In the present study, a total of 45 specimens of the brushtooth lizardfish Saurida undosquamis (family: Synodontidae) and 35 specimens of the red porgy seabream Pagrus pagrus (family: Sparidae) was examined for monogenean infestation. Samples were collected from water locations at Hurghada coasts along the Red Sea in Egypt. Two different species were recovered. The first recorded parasite was Diclidophora merlangi infesting the lizardfish. This parasite was morphologically similar to the original description for the general body shape, size, shape and arrangement of the clamps and reproduction organs and the number of spines in the lateral groups of the genital atrium, but is distinguished in the host fish which is of a different genus. The second species was Loxuroides pricei. The morphological and quantitative data of the isolated specimens and the potential reproductive consequences supported their assignment to L. pricei than to the other congeneric species. This parasite can be separated from the morphologically similar L. sasikala through having a shorter distance from the anterior extremity to genital atrium or vaginal region, fewer testes and a slightly greater number of spines on cirrus and genital atrium. The two species represented new host and locality records from the Red Sea in Egypt.

Sir Andrew Smith – his contributions and connections to freshwater ichthyology in southern Africa

Sir Andrew Smith (1797–1875), a medical officer in the British Army, was posted to South Africa from 1821 to 1837. During that time, he founded the South African Museum and made many valuable scientific contributions to a range of disciplines; however, his contributions to the discovery of freshwater fishes have not been specifically discussed. Smith was the first to publish descriptions of southern African freshwater fishes in South Africa. He described seven new species in his famed publication of “Illustrations”, a significant step forward in the knowledge of southern African freshwater fishes at the time. This article explores the contributions made by Sir Andrew Smith to freshwater ichthyology in South Africa.

Some nematodes from freshwater fishes in central Africa.

Twenty species (sixteen adult and four larval) of parasitic nematodes belonging to the Ascaridoidea, Camallanoidea, Cosmocercoidea, Dioctophymatoidea, Habronematoidea, Oxyuroidea, Seuratoidea, and Thelazioidea were collected from freshwater fishes of the Congo River basin in the Democratic Republic of the Congo and the Central African Republic in 2008 and 2012, respectively. Based on light and scanning electron microscopical examination, many species are redescribed in detail. This material also contained four previously unknown species, Labeonema longispiculatum sp. n. from Synodontis acanthomias Boulenger, Gendria longispiculata sp. n. from Schilbe grenfelli (Boulenger), G. sanghaensis sp. n. from Schilbe marmoratus Boulenger, and Cucullanus congolensis sp. n. from Auchenoglanis occidentalis (Valenciennes). The new species L. longispiculatum is mainly characterised by conspicuously long (210-228 µm) spicules, approximately twice as long as those in other congeners, the length (45-48 µm) of the gubernaculum and the host family (Mochokidae), whereas G. longispiculata by very long (1.2 mm) spicules, the shape of the oesophagus and cephalic vesicle, distribution of postanal papillae and the host family (Schilbeidae). Main characteristic features of G. sanghaensis are the presence of a hexagonal oral aperture surrounded by lip-like structures, the posterior portion of the oesophagus moderately expanded, spicules and the gubernaculum 414-438 µm and 54-57 µm long, respectively, deirids located at the level of the posterior end of the oesophagus and the absence of cervical alae. Cucullanus congolensis differs from congeneric species parasitising African freshwater and brackish-water fishes mainly in the absence of a ventral precloacal sucker and lateral preanal papillae, the presence of a large median precloacal papilla-like formation, spicules 480-489 µm long and the location of the excretory pore in the region of the oesophago-intestinal junction. Chabaudus Inglis et Ogden, 1965 is considered a junior synonym of Gendria Baylis, 1930 and, consequently, species listed in the former genus are transferred to the latter as G. alaini (Alfonso-Roque, 1981) comb. n., G. chabaudi (Inglis et Ogden, 1965) comb. n., G. dehradunensis (Rizvi, Bursey et Maity, 2016) comb. n., G. thysi (Puylaert, 1970) comb. n. and G. williamsi (Puylaert, 1970) comb. n. The findings represent many new host and geographical records.

Estimating δ15N fractionation and adjusting the lipid correction equation using Southern African freshwater fishes.

Stable isotope analysis is an important tool for characterising food web structure; however, interpretation of isotope data can often be flawed. For instance, lipid normalisation and trophic fractionation values are often assumed to be constant, but can vary considerably between ecosystems, species and tissues. Here, previously determined lipid normalisation equations and trophic fractionation values were re-evaluated using freshwater fish species from three rivers in the Upper Zambezian floodplain ecoregion in southern Africa. The parameters commonly used in lipid normalisation equations were not correct for the 18 model species (new D and I parameters were estimated as D = 4.46‰ [95% CI: 2.62, 4.85] and constant I = 0 [95% CI: 0, 0.17]). We suggest that future isotopic analyses on freshwater fishes use our new values if the species under consideration do not have a high lipid content in their white muscle tissue. Nitrogen fractionation values varied between species and river basin; however, the average value closely matched that calculated in previous studies on other species (δ15N fractionation factor of 3.37 ± 1.30 ‰). Here we have highlighted the need to treat stable isotope data correctly in food web studies to avoid misinterpretation of the data.

Name changes and additions to the southern African freshwater fish fauna

Changes made to the scientific names of southern African freshwater fishes since 2001 are explained and discussed. Adjustments to the phylogeny and classification of the fauna are outlined. Recent systematic studies on cyprinines are discussed and changes to the genera Labeobarbus (expanded concept), Pseudobarbus (expanded concept), and Enteromius are supported. The introduction of the family names Alestidae and Nothobranchiidae is discussed. Adjustments made to the genera Nannocharax, Micropanchax, Tilapia, Coptodon and Mastacembelus are explained. Species name changes for Hepsetus and Zaireichthys are detailed. New species described from the region, or resurrected from synonymy, since 2001 are listed.

Prevalence and characterization of plasmid-mediated quinolone resistance genes in Aeromonas spp. isolated from South African freshwater fish

An increasing incidence of multidrug-resistant Aeromonas spp., which are both fish and emerging opportunistic human pathogens, has been observed worldwide. Quinolone–resistant Aeromonas spp. isolates are increasingly being observed in clinical and environmental settings, and this has been attributed primarily to target gene alterations, efflux, and transferable quinolone resistance. Thirty-four Aeromonas spp., obtained from freshwater aquaculture systems, were screened for the presence of GyrA and ParC substitutions, efflux activity and the prevalence of plasmid-mediated quinolone resistance genes, qnr and aac-6′-Ib-cr. Although 44% of isolates were resistant to nalidixic acid, the majority were susceptible to ciprofloxacin and ofloxacin. The predominant GyrA substitution was Ser-83→Val among Aeromonas veronii isolates whilst Aeromonas hydrophila isolates displayed a Ser-83→Ile substitution, and Ser-80→Ile substitutions were observed in ParC. Minimum inhibitory concentrations of fluoro(quinolones) were determined in the presence and absence of the efflux pump inhibitor, phenylalanine-arginine β-naphthylamide (PAβN). Addition of PAβN had no effect on the levels of fluoro(quinolone) resistance observed for these isolates. Although no aac-6′-Ib-cr variant genes were identified, qnrB and qnrS were detected for 41% and 24% of isolates, respectively, by Southern hybridization and confirmed by PCR and sequencing. Quinolone resistance in these fish-associated Aeromonas isolates was related to mutations in the quinolone resistance determining regions of GyrA and ParC and presence of qnrB and qnrS. The presence of qnr alleles in Aeromonas spp. isolates may facilitate high-level fluoroquinolone resistance and potentially serve as reservoirs for the dissemination of qnr genes to other aquatic microbes.

Molecular phylogeny and biogeography of African diploid barbs, ‘Barbus’, and allies in Africa and Asia (Teleostei: Cypriniformes)

African diploid barbs (‘Barbus’, Clypeobarbus, Barboides, etc.) are a group of small cyprinids with a body size less than 20 cm and widely distributed in drainages across Africa. These species constitute a significant component of African freshwater fish fauna. This study is the first to focus on the molecular systematics and biogeography of African diploid barbs ‘Barbus’ and its African and Asian allies using both mitochondrial and nuclear genes. We test for monophyly of groups, determine interspecific relationships and estimate the time of divergence of 52 species of ‘Barbus’ and allies using two mitochondrial and four nuclear genes. Resulting trees demonstrate that ‘Barbus’ and allies (Systomus, Barboides, Clypeobarbus and African tetraploid barbs) form a strongly supported clade; however, ‘Barbus’ is not resolved as monophyletic. Divergence time analyses identify the separation between Systomus and ‘Barbus’ plus African allies may have occurred around 26 MYA. In addition to the phylogenetic results, these findings highlight the need for more thorough taxonomic and systematic studies on ‘Barbus’ and allies using morphological and additional molecular data and greater taxon sampling, including the type species of the genus Enteromius, ‘Barbus’ potamogalis.

A Fish Assemblage from the Middle Eocene from Libya (Dur At-Talah) and the Earliest Record of Modern African Fish Genera.

In the early nineteen sixties, Arambourg and Magnier found some freshwater fish (i.e., Polypterus sp., Siluriformes indet. and Lates sp.) mixed with marine members in an Eocene vertebrate assemblage at Gebel Coquin, in the southern Libyan Desert. This locality, aged ca 37–39Ma and now known under the name of Dur At-Talah, has been recently excavated. A new fish assemblage, mostly composed of teeth, was collected by the Mission Paléontologique Franco-Libyenne. In this paper, we describe freshwater fish members including a dipnoan (Protopterus sp.), and several actinopterygians: bichir (Polypterus sp.), aba fish (Gymnarchus sp.), several catfishes (Chrysichthys sp. and a mochokid indet.), several characiforms (including the tiger fish Hydrocynus sp., and one or two alestin-like fish), and perciforms (including the snake-head fish Parachanna sp. and at least one cichlid). Together with the fossiliferous outcrops at Birket Qarun in Egypt, the Libyan site at Dur At-Talah reduces a 10-Ma chronological gap in the fossil record of African freshwater fish. Their fish assemblages overlap in their composition and thus constitute a rather homogenous, original and significant amount of new elements regarding the Paleogene African ichthyofauna. This supports the establishment of the modern African freshwater fish fauna during this time period because these sites mostly contain the earliest members known in modern genera.