Abstract
Identification of limpets is often hampered by highly variable within-species shell morphologies and colour patterns. Since pre-Linnean times this has produced complex taxonomies with confusing nomenclatorial histories and uncertain distribution patterns. This is the case for a complex of taxa associated with Cymbula safiana (Lamarck, 1819) and with the rejected name Patella nigra. We DNA sequenced limpets from Nigeria that were originally identified as C. safiana. Comparisons with available cox1 data of patellogastropods show that the specimens actually belong to the genus Cellana Adams, 1869 which has been recorded only once before in the Atlantic Ocean with the finding of specimens from Ghana. We are reporting findings of Cellana sp. from the Gulf of Guinea for the second time. Specimens from Nigeria are 100 % similar to previously published cox1 sequences from Ghana. Due to variable shell characteristics we suspect that this species may have been confused with Cymbula safiana (Lamarck, 1819) in previous records. Inspection of the radula sack and radula demonstrates clear similarities with other Cellana species and contrasting differences in the organization of the teeth in Cymbula. Because Cellana is a possible candidate of invasive species in West Africa and Cymbula is considered as endangered, is seems particularly important to be able to distinguish between the two without being dependent on DNA analysis. When shell morphology seems to be of questionable diagnostic value, examination of the radula will help in future mapping and monitoring of these two species. A cox1 gene tree with Nigerian sequences included is in line with findings of previous authors and restates the need for taxonomic revision of the species clustering with Cellana toreuma (Reeve, 1854) and parts of a polyphyletic Cellana radiata von Born, 1778.
Highlights
Identification of limpets is often hampered by highly variable within-species shell morphologies and colour patterns
As a result of an initiative to produce DNA-barcodes for Nigerian molluscs via BOLD (Ratnasingham and Hebert 2007) we discovered that mitochondrial cytochrome subunit 1 sequences from five Nigerian specimens initially identified as Cymbula safiana had 100 % nucleotide similarity with the African Cellana sequences discussed by Nakano and Sasaki (2011; Christianens 1974)
We report these findings to supplement the discovery of Nakano and Espinosa (2013) with additional information that will hopefully contribute to more accurate records of limpet species in West Africa
Summary
Identification of limpets is often hampered by highly variable within-species shell morphologies and colour patterns. Identification of limpets is often hampered by highly variable shell morphologies and colour patterns within species (Nakano and Sasaki 2011). This has produced complex taxonomies and nomenclatorial histories that are expressed in sometimes lengthy lists of synonyms and misidentified records (Christianens 1974; Gofas 2016). Cymbula safiana is regarded as an endangered species in Europe, it is still listed as being distributed all the way from the Iberian Peninsula to Angola (Espinosa et al 2011) Molecular evidence for this was found in the close similarity of 16S sequences from Angola and Spain (Koufopanou et al 1999)
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