Hard Clams (Mercenaria mercenaria) Evaluate Predation Risk Using Chemical Signals from Predators and Injured Conspecifics

Abstract

Abstract-Hard clams, Mercenaria mercenaria, are sessile, filter-feeding organisms that are heavily preyed upon by blue crabs, which find their clam prey using chemical cues. Clams may evade blue crabs by reducing their pumping (feeding) behavior when a threat is perceived. The purpose of this study was to determine the type of signals that clams use to detect consumers. Clams decreased their pumping time in response to blue crabs and blue crab effluent, but not to crab shells, indicating that chemical signals and not mechanical cues mediated the response of clams to distant predators. Because predator diet can influence prey evaluation of predatory threats, we compared clam responses to blue crabs fed a steady diet of fish, clams, or that were starved prior to the experiment. In addition, we used injured clams as a stimulus because many organisms detect predators by sensing the odor of injured con-or heterospecifics. Clams reduced feeding in response to injured conspecifics and to blue crabs that had recently fed. Clams reacted similarly to fed crabs, regardless of their diet, but did not respond to starved blue crabs. Because blue crabs are generalist predators and the threat posed by these consumers is unrelated to the crab's diet, we should expect clam reactions to blue crabs to be independent of the crab's diet. The failure of clams to react to starved blue crabs likely increases their vulnerability to these consumers, but clam responses to injured conspecifics may constitute a strategy that allows animals to detect an imminent threat when signals emanating from blue crabs are not detectable.

Sedentary prey facing an acute predation risk: testing the hypothesis of inducible metabolite emission suppression in zebra mussels, Dreissena polymorpha

“…If the mechanisms predicted by the HIMES actually occur, this would help explain some unexpected patterns that have been reported in earlier studies on different species of bivalves. In marine bivalves, the presence of predation cues was found to reduce byssus production and mobility in Hormomya mutabilis (Ishida & Iwasaki, 2003), food intake in Mercenaria mercenaria (Smee & Weissburg, 2006) and respiration rates in Perumytilus purpuratus (Vial et al, 1992;Lopez et al, 1995). In zebra mussels, cues from injured conspecifics have been found to reduce mobility (Toomey et al, 2002;Czarnoleski et al, 2010b), clearance rates (Naddafi et al, 2007;Naddafi & Rudstam, 2014) and attachment strength (Czarnoleski et al, 2010b(Czarnoleski et al, , 2011, and to bias filter-feeding towards easy-to-digest foods (Naddafi et al, 2007).…”

“…Based on the findings of Czarnoleski & Muller (2014), we hypothesized that zebra mussels would reduce their emission of disclosing metabolites when they receive cues about foraging predators. Upon foraging, common predators of bivalves, such as fish and crustaceans, use prey metabolites to sense the location of their prey (Hazlett, 1994;Weissburg and ZimmerFaust, 1994;Weissburg et al, 2002), but the hypothesis of inducible metabolite emission suppression (HIMES) has rarely been addressed by earlier studies (but see Weissburg and Zimmer-Faust, 1994;Smee & Weissburg, 2006;Czarnoleski & Muller, 2014). Over the last two centuries, Ponto-Caspian zebra mussels have expanded to diverse environments in Europe and North America (http://www.europe-aliens.org/), facing a variety of pressures from local predators (Czarnoleski et al, 2010a).…”

Trait-mediated indirect interactions among residents of rocky shore tidepools

“…might not learn that the risk of predation abates as they grow (Yarnall 1964). A third explanation for the similar response of all sizes of snails is that seastars starved for 24 h might not have emitted strong threat cues because recent ingestion of hetero-or conspecifics can increase perception of risk cues by prey, causing stronger avoidance of predators (Jacobsen & Stabell 2004, Smee & Weissburg 2006, Weissburg & Beauvais 2015. This did not appear to be the case in our experiments.…”

Mangrove expansion into temperate marshes alters habitat quality for recruiting Callinectes spp.

“…To assess the influence of risk on habitat preference, 2 portunid predators (described in the previous section) were added to each standpipe in half the trials. Meshcovered openings between the standpipe and each section allowed predator chemical cues to enter the arena without any risk of actual predation (Griffiths & Richardson 2006, Smee & Weissburg 2006. Aeration within each standpipe increased water flow, circulating predator cues from the pipe into the broader arena.…”