title: Not as docile as it looks? Loxosceles venom variation and loxoscelism in the Mediterranean Basin and the Canary Islands.
abstract: The medical importance of Loxosceles spiders has promoted extensive research on different aspects of their venoms. Most of the reported cases of loxoscelism have occurred in the Americas, and thus, much work has focused on North and South American Loxosceles species. Interestingly, loxoscelism cases are rare in the Mediterranean Basin although Loxosceles rufescens, endemic to the Mediterranean, is an abundant spider even in human-altered areas. Thus, it has been suggested that the venom of L. rufescens could be of less medical relevance than that of its congeners. In this study, we challenge this hypothesis by using multiple approaches to study venom variation in selected species and lineages from the Mediterranean Basin and the Canary Islands. We found that SMase D activity, the key bioactive component of Loxosceles venom, is comparable to American species that are confirmed to have medically relevant bites. The venom protein composition using SDS-PAGE presents some differences among regional Loxosceles taxa in banding pattern and intensity, mostly between the Canarian and L. rufescens lineages. Differences between these species also exist in the expression of different paralogs of the SicTox gene family, with the Canarian species being less diverse. In conclusion, our results do not support the challenged hypothesis, and suggest that venom of these species may indeed be as potent as other Loxosceles species. Pending confirmation of loxoscelism with direct evidence of Loxosceles bites with species identification by professionals, Loxosceles in the Mediterranean region should conservatively be considered medically relevant taxa.
authors.affiliation: Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona, 08028 Barcelona, Spain.
authors.forename: Enric
authors.initials: E
authors.lastname: Planas
authors.affiliation: Department of Biology, Lewis & Clark College, 0615 SW Palatine Hill Rd., Portland, OR 97219, USA.
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Zobel-Thropp
authors.affiliation: Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona, 08028 Barcelona, Spain.
authors.forename: Carles
authors.initials: C
authors.lastname: Ribera
authors.affiliation: Department of Biology, Lewis & Clark College, 0615 SW Palatine Hill Rd., Portland, OR 97219, USA. Electronic address: binford@lclark.edu.
authors.forename: Greta
authors.initials: G
authors.lastname: Binford
mesh_terms: D001483:Base Sequence; D001499:Bayes Theorem; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D019083:Mediterranean Region / Q000453:epidemiology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010078:Oxazines; D010727:Phosphoric Diester Hydrolases / Q000235:genetics* / Q000633:toxicity*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013030:Spain / Q000453:epidemiology; D013045:Species Specificity; D001098:Spider Bites / Q000453:epidemiology* / Q000503:physiopathology*; D013111:Spider Venoms / Q000201:enzymology* / Q000633:toxicity
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D010078:Oxazines; D013111:Spider Venoms; C470430:Amplex Red; D010727:Phosphoric Diester Hydrolases; C055160:sphingomyelin phosphodiesterase D
keywords: Evolution; SDS-PAGE; SicTox; Sphingomyelinase D (SMase D); Spider