Biodiversity of the freshwater crabs of Benin (Potamonautidae): a genetic approach

Introduction: Published reports on freshwater crabs in Benin (West Africa) are very scarce and mention only two accepted taxa: Sudanonautes aubryi and S. monodi (the latter with no precise locality). The inventory of these species (described using specimens from Gabon and Cameroon, respectively) is still poorly known. Methods: Here, we explore the diversity of freshwater crabs in Benin using a selection of 18 specimens collected in 2022 and 2023 in a range of aquatic biotopes and throughout the country, except for the far north. The specimens were examined morphologically and sequenced for fragments of the COI, 16S and H3 genes. Results: Despite a general variability in color, shape, size and in the DNA sequences (proportion of substitution per site up to ca. 8% for COI, 3% for 16S and 0.3% for H3), our results suggest that all the Beninese crabs belong to a single species of the Sudanonautes genus. They also show that they are neither S. aubryi nor S. floweri, with which they show consistent morphological differences and larger proportions of substitution per site at COI (>10%), 16S (>6%) and H3 (>0.6%). Conclusions: The Beninese crabs may belong to an undescribed species. However, they are more likely conspecific with S. pelii, a species described from the coastal plain of Ghana, previously considered to be a junior synonym of S. aubryi, and whose lectotype’s photographs show no obvious morphological differences with the Sudanonautes crabs from Benin. It is therefore likely that S. pelii will have to be revalidated for certain populations of Sudanonautes crabs from Ghana, Benin and probably adjacent countries.

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