Evolutionary Patterns in Trace Metal (Cd and Zn) Efflux Capacity in Aquatic Organisms

Abstract

The ability to eliminate (efflux) metals is a physiological trait that acts as a major driver of bioaccumulation differences among species. This species-specific trait plays a large role in determining the metal loads that species will need to detoxify to persist in chronically contaminated environments and, therefore, contributes significantly to differences in environmental sensitivity among species. To develop a better understanding of how efflux varies within and among taxonomic groupings, we compared Cd and Zn efflux rate constants (ke values) among members of two species-rich aquatic insect families, Ephemerellidae and Hydropsychidae, and discovered that ke values strongly covaried across species. This relationship allowed us to successfully predict Zn efflux from Cd data gathered from aquatic species belonging to other insect orders and families. We then performed a broader, comparative analysis of Cd and Zn ke values from existing data for arthropods, mollusks, annelids, and chordates (77 species total) and found significant phylogenetic patterns. Taxonomic groups exhibited marked variability in ke magnitudes and ranges, suggesting that some groups are more constrained than others in their abilities to eliminate metals. Understanding broader patterns of variability can lead to more rational extrapolations across species and improved protectiveness in water-quality criteria and ecological assessment.

Calcium uptake in aquatic insects: Influences of phylogeny and metals (Cd and Zn)

“…This finding is consistent with other studies (Buchwalter et al, 2008;Poteat et al, 2013) that demonstrate a strong phylogenetic basis for differences across species in ion (metal) transport processes. Our data also suggest that Ephemerellidae is a more physiologically variable group than is Hydropsychidae.…”

The importance of retaining a phylogenetic perspective in traits‐based community analyses

“…Phylogeny, body weight at the time of experimentation and feeding guild all failed to explain the variation of k e values observed across species . This result contrasts with our previous work that showed how Cd k e values exhibit phylogenetic signal across four aquatic phyla, Annelida, Arthropoda, Chordata and Mollusca (Poteat et al ., ), and even within many of the same EPT genera examined here (Buchwalter et al ., ). The Buchwalter et al .…”

“…Possible K ‐statistic values range from 0 to ∞, with K = 0 indicating no phylogenetic signal and K = 1 indicating traits which are similar to what would be expected under the influence of Brownian motion. Three arbitrary branch lengths [all branches set to equal 1, Pagel's arbitrary (Pagel, ) and Grafen's arbitrary (Grafen, )] were employed to determine the branch lengths which resulted in the highest ln likelihood (the branch lengths which fit the data best; see Poteat et al ., ). The K ‐statistic from the tree with the highest ln likelihood was then used.…”

Assessment of water quality in urban streams based on larvae of Hydropsyche angustipennis (Insecta, Trichoptera)

“…Our findings confirm that this species is capable of accumulating certain amounts of heavy metals even if their concentration in water is low (Girgin et al 2010), as it has been detected in other Hydropsyche species (Cain and Luoma 1998;Barata et al 2005). For previous studied Hydropsyche spp., the metal uptake and efflux were on the similar level irrespective of studied species (Evans et al 2002;Cain et al 2006;Poteat et al 2013;Poteat et al 2015). Taking into consideration the kinetics of metal presence in larvae, the biological half-life of kind of heavy metals, e.g., Cd or Zn, is relatively short (on the order of several weeks) for these caddisflies.…”