LB 31-301 - CANCELLED - Non-consumptive effects of oyster predators regulate the feeding of both their prey and its ectoparasites

Background/Question/Methods:

Predators and parasites can powerfully regulate the feeding behavior of the organisms which they attack and, in doing so, indirectly influence broader patterns of ecosystem structure and functioning. However, little is known about how predators influence the behavior of parasites and whether non-consumptive predator effects may have cascading impacts on hosts. Using lab behavioral response assays, we examined the effects of predatory mud crab (Panopeus herbstii) scent cues on the feeding behavior of an abundant ectoparasitic snail that attacks the eastern oyster (Crassostrea virginica) in the southeastern US.

Results/Conclusions:

The behavioral response assay revealed that ectoparasites reduced feeding activity in the presence of crab scent cues. A subsequent lab biofiltration assay revealed that, at low and medium ectoparasite densities, the biofiltration rate of oysters exposed to predator scent cues was moderately reduced. However, at high ectoparasite densities, crab scent cues enhanced oyster biofiltration rate. These results demonstrate that the strength and direction of intensity-dependent ectoparasite impacts on oysters can be mediated by crab scent cues, underscoring the complex web of trait-mediated interactions that potentially influence oyster reef functioning. Considering that predators strongly regulate parasite densities in many ecosystems through direct consumption, it is likely they also influence parasite behavior through non consumptive effects with potential cascading impacts on hosts.