An analysis of geographic and intersexual chemical variation in venoms of the spider Tegenaria agrestis (Agelenidae).

The spider Tegenaria agrestis is native to Europe, where it is considered medically innocuous. This species recently colonized the US where it has been accused of bites that result in necrotic lesions and systemic effects in humans. One possible explanation of this pattern is the US spiders have unique venom characteristics. This study compares whole venoms from US and European populations to look for unique US characteristics, and to increase our understanding of venom variability within species. This study compared venoms from T. agrestis males and females from Marysville, Washington (US), Tungstead Quarry, England (UK) and Le Landeron, Switzerland, by means of liquid chromatography; and the US and UK populations by insect bioassays. Chromatographic profiles were different between sexes, but similar within sexes between US and UK populations. Venoms from the Swiss population differed subtly in composition from UK and US venoms. No peaks were unique to the US population. Intersexual differences were primarily in relative abundance of components. Insect assays revealed no differences between US and UK venom potency, but female venoms were more potent than male. These results are difficult to reconcile with claims of necrotic effects that are unique to venoms of US Tegenaria.