The Congolese and Lower Guinean ichthyological provinces are understudied hotspots of the global fish diversity. Here, we barcoded 741 specimens from the Lower and Middle Congo River and from three major drainage basins of the Lower Guinean ichthyological province, Kouilou‐Niari, Nyanga and Ogowe. We identified 194 morphospecies belonging to 82 genera and 25 families. Most morphospecies (92.8%) corresponded to distinct clusters of DNA barcodes. Of the four morphospecies present in both neighbouring ichthyological provinces, only one showed DNA barcode divergence <2.5%. A small fraction of the fishes barcoded here (12.9% of the morphospecies and 16.1% of the barcode clusters representing putative species) were also barcoded in a previous large‐scale DNA analysis of freshwater fishes of the Lower Congo published in 2011 (191 specimens, 102 morphospecies). We compared species assignments before and after taxonomic updates and across studies performed by independent research teams and observed that most cases of inconsistent species assignments were due to unknown diversity (undescribed species and unknown intraspecific variation). Our results report more than 17 putative new species and show that DNA barcode data provide a measure of genetic variability that facilitates the inventory of underexplored ichthyofaunae. However, taxonomic scrutiny, associated with revisions and new species descriptions, is indispensable to delimit species and build a coherent reference library.
Microbial consortium that is present in fish gut systems works together to achieve unknown specific roles. Here, we collected guppy fish from hydrocarbon- and trace metal-contaminated wastewater to assess the relationships between gut microbiota and host fish adaptation. Targeted genes and 16S rRNA amplicon sequencing have been used to identify gut bacteria of guppies. Mineral-conditioned medium contributes to identify bacteria with the ability to grow and/or to tolerate hydrocarbon and trace metals. Additionally, trace metals’ tolerance minimum inhibitory concentration (MIC) of microbiota was evaluated. We first isolated bacteria from the gut system, and we showed that Bacillus spp., Staphylococcus spp., Shigella spp., Salmonella spp, Pseudomonas spp., Citrobacter spp., Salmonella enterica ssp.arizonae sp., Enterobacter spp, and Acinetobacter spp. are part of guppy gut microbiota. Some representative species are able to degrade and/or tolerate gasoline and/or diesel fuel hydrocarbons. Tolerance to trace metals was observed in Gram-positive and Gram-negative bacteria. We showed that minimal inhibitory concentration (MIC) of some microbiota isolated from gut systems has been found including for mercury (Hg) between 2 and 4‰, cobalt (Co) Co (2 and 5‰), zinc (Zn) (9 and 18‰), and plomb (Pb) (22 and 27‰). Zn and Pb were the trace metals for which the rate of tolerance was significantly higher. Finally, we showed that cytochrome c oxidase is not interfering in presence of trace metals. The working consortium showed that bacteria should work together to achieve their best.
Steered fermentation by microorganisms gives great added value in the nutritional quality of local food. Ginger rhizome naturally contains a myriad of bioactive compounds including polyphenol and flavonoids. The aim of this work was to ferment the ginger juice, to evaluate the biochemical parameters of ginger wine, and to understand the involvement of microorganisms in the bioincrease of polyphenol compounds. Titratable acidity and pH values were determined and showed that pH is around 1.6 at the end of the fermentation when the acidity is around 6.431 g/L. Using colorimetric assay, the total polyphenolic and flavonoid compounds were evaluated throughout the fermentation. The variation of the polyphenol and flavonoid concentrations of the unsweetened sample was around 10.18 to 14.64 mg Eq AG/g and 1.394 to 2.224 mg Eq Cat/g Ms, but those from the sweet sample were around 10.82 to 18.34 mg Eq AG/g Ms and 1.311 to 2.290 mg Eq Cat/g. Using one-step PCR, multiplex techniques with specific primers, with yeast-like phenotype 27.27% (6), have been assigned among 22 isolates to Saccharomyces cerevisiae. By using PCR multiplex techniques, Bacillus licheniformis, Bacillus pumilus, Bacillus safensis, and Saccharomyces cerevisiae have been identified. Together with Saccharomyces cerevisiae, we showed that Bacillus sp. are able to secrete enzymatic landscape with some activities up to 50% including cellulase, amylase, pectinase, and protease.
A new species of smiliogastrin cyprinid is described from the Louesse, Lekoumou (upper Niari basin), and Djoulou (upper Ogowe basin) rivers in the Republic of Congo, west-central Africa. The new species is readily distinguished from congeners by the pres¬ ence of a flexible, weakly ossified and smooth bordered last unbranched dorsal-fin ray, well-developed barbels, and a straight and complete lateral line in combination with a characteristic pigmentation patterning consisting of a distinctive, rounded black spot at the base of and extending over the first rays of the anal fin and a prominent, darkly pigmented blotch over the base of the anterior dorsal-fin rays. A combination of morphological fea¬ tures and pigmentation patterning that appears to be unique among Enteromius. The new species is widespread throughout the Louesse-Djoulou region, and the fact that such a seemingly common species has gone undetected until now serves to underscore how poorly known this region of the Republic of Congo remains.
Ichthyofaunal diversity and the impact of anthropogenic activities on fish population assemblages were studied in Lake Cayo, a small lake located in the coastal region of the Republic of Congo. Twelve stations were sampled twice over a two-year period. Fishing techniques following standardized methods utilizing monofilament gill nets, and nine environment variables were measured at each station. A total of 11,361 specimens comprising 30 species in 28 genera and 18 families were collected with the Cichlidae being the most diversified. Redundancy Analysis with forward selection coupled with Monte Carlo permutation tests identified depth, pH and substrate as accounting for 57.7% of the total variance among the nine variables sampled (p < 0.05). The low Shannon's diversity (1.16 ± 0.33) and Equitability (0.43 ± 0.12) indices at all sites, suggest that the Lake Cayo system is in poor ecological health.
The African cyprinid genus Labeobarbus is characterized by a high polymorphism in mouth morphology. The association between four species of this genus (two chiselmouths, one rubberlip with a well-developed fleshy mental lobe on the lower jaw, i.e., a fleshy appendage on the chin, and one usually with a poorly developed one) and 26 environmental variables was investigated in four affluents of the Luhoho River in the Albertine Highlands of the Upper Congo basin. A combination of univariate and multivariate analyses suggested that differences exist in habitat composition at localities where different Labeobarbus species were reported, and within different mouth phenotypes. The association of L. longidorsalis with the presence of cobbles and pebbles and of L. brauni with the presence of boulders suggests that the occurrence of chiselmouths phenotype is associated with stony habitats, whereas phenotypes with a mental lobe, i.e., Labeobarbus longifilis and L. paucisquamatus, mostly occupy habitats without stones. Differences in the distribution between these two species appear to be linked to physico-chemical parameters such as electrical conductivity and water temperature rather than substrate type. The findings of this study are relevant for developing guidelines that aim effective local preservation and conservation of these Labeobarbus species.
The present study reports on length-weight relationships (LWRs) for 37 of the most abundant fish species in the Lefini River basin, one of the largest right bank tributaries of the Congo River in the Republic of the Congo. The study area comprised 12 stations along 103 km of the river. Each station was sampled during March 2007 to August 2008 following standardized methods utilizing five monofilament gill nets of 10, 12, 15, 20 and 30 mm mesh size. Sample size, lengths, weights, LWRs, 95% confidence intervals of a and b, coefficient of correlation r 2 and growth type are provided for each species. Values of allometric coefficient b of the LWRs (W = aSL b ) ranged from 2.556 for Synodontis nigriventris to 3.363 for Brycinus poptae. These results represent the first study of length-weight relationships for fish species in a large affluent of the Congo basin as a whole. K E Y W O R D S fish, lefini river, length-weight relationship, middle Congo How to cite this article: Ibala Zamba A, Vreven E, Mamonekene V, Musschoot T, Poaty Ngot HF, Snoeks J. Length-weight relationships of 37 freshwater fish species from the Lefini river, middle Congo River basin (Republic of the Congo). J Appl Ichthyol. 2020;36:355-360. https://doi.
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