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Poster Display

Physiology, Biochemistry, and Toxicology

Poster: PBT, Physiology and Toxicology

D3381: Effects of body size and season on total and methyl mercury concentrations in orb-weaving spiders

Tuesday, November 12, 2024
9:00 AM – 5:00 PM MST
Location: Phoenix Convention Center, Exhibit Hall 6, PCC
Poster Display
Riparian spiders have been proposed as sentinels of bioaccumulative contaminants, like methylmercury (MeHg).  Riparian spiders become contaminated with MeHg when they feed on emergent aquatic insects and concentrations of MeHg in riparian spiders reflect the level of contamination of the aquatic food web.  Although previous studies suggest riparian spiders have potential as sentinels of MeHg, few studies have examined how MeHg concentrations in riparian spiders vary seasonally.  We sampled two genera of orb-weaving spiders (Araneidae: Larinioides sp. and Metazygia sp.) monthly from May-September 2019 at a private boat dock on Eagle Mountain Lake, Texas. We collected 574 spiders and separated them by, genera, size class and month of collection into composite samples. The samples were then analyzed for total Hg (THg, inorganic+MeHg) and MeHg.  We observed no difference in THg concentration between genera and so combined them for subsequent analyses.  During most months we observed a positive correlation between THg concentration and spider size, indicative of age-dependent Hg bioaccumulation, but the slope of the relationship between THg and size increased throughout the summer.  As a consequence, the highest concentrations of THg occurred in the largest spiders in late summer and fall.   Unlike, total Hg, MeHg concentrations were low and remained constant over the course of the study, resulting in a steady decrease in %MeHg in spider tissues.  We hypothesize that these patterns were caused by an increasing reliance on terrestrial insect prey (with low % of MeHg) through the summer.