Antipredatory Behavior as an Index of Heavy-Metal Pollution? A Test Using Snails and Caddisflies

Abstract

The loss of behaviors that organisms use to avoid predation may serve as a sensitive indicator of pollution. We tested the hypothesis that a correlation exists in the field between heavy metal levels and antipredator behaviors. We examined the antipredator behavior of aquatic caddisfly larvae and snails at sites in the Coeur d'Alene basin of Northern Idaho which varied in their levels of heavy metals. We tested the antipredator response of Physella columbiana snails at 10 polluted lakes downstream from the Bunker Hill Environmental Protection Agency (EPA) Superfund cleanup site. We then compared their behavior to snails at 14 reference lakes. We placed the snails in a plastic testing apparatus, exposed them to an extract of crushed snail, and then monitored their movements to a normally preferred shaded area. We also tested the behavior of caddisfly larvae from 36 sites from a total of 6 streams/rivers adjacent to the Superfund site. Sites were located upstream and downstream of abandoned mines. We located active larvae of four genera, simulated predation by grasping the animals between thumb and forefinger (the larvae respond to being grasped by withdrawing into their case), lifted them from the water for 3 s, and then placed them in an adjacent, slower section of the stream. We then recorded how long it took each larvae to partially emerge from its case and attempt to move away. Unlike reference site snails, snails from heavy metal-polluted environments failed to exhibit antipredator behaviors in response to crushed conspecifics. These results are consistent with previous laboratory studies. We found no effect of heavy metals on the antipredatory behavior of caddisfly larvae.

Terrestrial snails use predator-diet to assess danger

“…Because the number of snails was limited and the egg laying experiment was set up after the results of the climbing experiment were known (no significant effect of crushed snail extract), we did not include a crushed snail extract treatment. Past experience (Lefcort et al 2000(Lefcort et al , 2002 has indicated that many snails have a very strong "all or nothing" response to snail extract. Every day, five drops of treatment solution were placed in each container.…”

“…No anesthesia other than cooling was used, since the anesthesia may have altered the behavior of test snails. Both the snail extract and the fecal solution were filtered (see Lefcort et al 2000). Each snail was exposed to each of the four treatments on separate days; and the order of treatments was randomized.…”

“…For instance, the presence of chemical cues from injured conspecifics alter the distributions of spider mites (Tetranychus urticae; Grostal and Dicke 1999). Marine gastropods grow more predator-resistant shells when exposed to damaged conspecifics (Appleton and Palmer 1988) and aquatic pulmonate snails typically stop moving and withdraw into their shells when presented with a stimulus from damaged conspecifics (Turner 1996;Dewitt et al 1999;Lefcort et al 2000). The effect of damaged conspecifics has not been tested on terrestrial snails.…”

“…Movements and latency to egg laying are easily measured snail behaviors that may be correlated to predator avoidance. Given the responses of other pulmonate snails (Lefcort et al 2000), we also tested whether an extract of crushed snails, i.e., damaged cells without predator odor, would influence snail movements and egg laying.…”

Mining Impacts on the Fresh Water Environment: Technical and Managerial Guidelines for Catchment Scale Management

“…More subtle changes involve indirect effects of metals in species interactions and community function, resulting from alterations in the physiology and/or behaviour of the various organisms. For example, metal exposure affected the territorial behaviour in hydropsychid larvae, relaxing the levels of interspecific competition (Vuori 1994), causing benthic invertebrates to be more susceptible to predation (Clements et al 1989;Clements 1999;Kiffney 1996;Lefcort et al 2000) and increasing the mortality rate of parasitized amphipods and snails (Brown and Pascoe 1989;Guth et al 1977). However, these effects are likely to vary among populations, communities, and ecosystems in different geographical areas.…”