Phylogenetically mediated anti-predator responses in bivalve molluscs

Abstract

Sedentary, group-living taxa, such as bivalves, respond to waterborne predator cues by enhancing tissues that increase anti-predation attributes such as muscle and shell mass. The ability of bivalves to differentiate among cues generated by the consumption of different prey species that vary in phylogenetic relatedness is unknown. We exposed mussels to cues generated by crabs feeding on mussels, cockles and periwinkles to test whether there was a relationship between the magnitude of the induced response and the level of relatedness to the cue source. Mussels exposed to either effluents of unfed crabs or seawater only served as controls. Exposure to cues from conspecifics and cockles caused significantly reduced growth in shell size of mussels compared to control mussels. Shell growth of mussels exposed to cues from crabs feeding on periwinkles did not differ significantly from mussels exposed to effluents from unfed crabs only. Tissue dry weight increased least in mussels exposed to cues of crabs fed conspecifics, followed by mussels exposed to crabs fed cockles. Cues of crabs that were fed mussels caused increased byssus thread production, whereas the other treatments did not. Exposure to cues from crabs fed mussels and crabs fed cockles resulted in significantly thicker and heavier shells compared to unexposed control mussels. The results of this study indicate that alarm cues of progressively more closely related molluscs cause a higher degree of induced morphological anti-predator responses in mussels. The physiological and behavioural responses of mussels to these cues may therefore have a phylogenetic basis. KEY WORDS: Alarm cues · Heterospecifics · Inducible defences · Mytilus edulis · Phylogenetic relationshipResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 363: 217-225, 2008 1996, Leonard et al. 1999, Smith & Jennings 2000, Reimer & Harms-Ringdahl 2001, Freeman & Byers 2006. Furthermore, these responses are specific in character since attack modes vary considerably between predators. Leonard et al. (1999) reported that mussels produced thicker shells when exposed to cues from crabs Carcinus maenas and to cues from damaged conspecifics. Smith & Jennings (2000) observed the same response when they exposed mussels to effluents from whelks Nucella lapillus and crabs. Thickening the shell provides effective protection against drilling and crushing predators, but is less effective against predators that use different predation strategies. Starfishes, for example, pull the shell valves apart using their tube feet and insert their stomach through the resulting aperture (Norberg & Tedengren 1995). Accordingly, mussels exposed to cues from starfish Asterias rubens were found to increase the mass of their adductor muscles to resist higher pulling forces (Reimer & Tedengren 1996, Reimer & HarmsRingdahl 2001. Other responses to predator cues are enhanced byssus thread production (Côté 1995, Leonard et al. 1999, Reimer & Harms-Ringdahl 2001 and clumping be...

Predatory blue crabs induce byssal thread production in hooked mussels

“…The lack of a significant interaction between mussel size and predator treatment could be because small mussels are already producing byssal threads at a maximal rate that cannot be increased further, or it could be due to the fact that members of all size classes of mussels can be consumed by blue crabs. As noted previously, inducible byssal thread production in the mussel Mytilus edulis is well known (Coˆte´1995; Coˆte´& Jelnikar 1999; Leonard et al 1999;Smith & Jennings 2000;Reimer & Harms-Ringdahl 2001;Freeman & Byers 2006;Fa¨ssler & Kaiser 2008), and the presence of predators also induces changes in shell morphology in members of this species (Leonard et al 1999;Reimer & Harms-Ringdahl 2001). Individuals of M. edulis also aggregate in the presence of the scent of predators (Cô te´& Jelnikar 1999; Leonard et al 1999;Smith & Jennings 2000;Reimer & Harms-Ringdahl 2001;Fa¨ssler & Kaiser 2008).…”

Size matters for risk assessment and resource allocation in bivalves

“…Smaller mussels did not reduce soft tissue growth in predator treatments even though they grew a thicker shell. This may have occurred because mussels produce additional byssal threads in response to predators to make it more difficult for predators to dislodge and crush them (Cote 1995, Leonard et al 1999, Fassler & Kaiser 2008. Soft tissue mass included mass from byssal threads, and thus we were unable to determine if mussels were allocating soft tissue growth differently in predator treatments (Fig.…”

“…For example, predator-induced behavioral changes such as a reduction in prey foraging time (Turner 2004, Large & Smee 2010 or feeding cessation (Smee & Weissburg 2006, Naddafi et al 2007 can minimize predation risk, but may ultimately lower growth and fecundity (Relyea 2001, 2002, Fassler & Kaiser 2008, Bourdeau 2010. Constant exposure to risk may also decrease body size and increase the likelihood of being consumed (Edeline et al 2010).…”

Clumping behavior and byssus production as strategies for substrate competition in Mytilus edulis

“…Therefore, it is reasonable to expect that competition between M. edulis and S. rustica is more intense than between M. edulis and H. arctica , which may explain differences in the aggregation and attachment responses of the mussels towards S. rustica and H. arctica . The mechanisms behind how the mussels can differentiate between the two potential competitors are not known, but may involve chemical cues as has been shown in predator recognition by mussels and other bivalves (Smith & Jennings ; Fässler & Kaiser ; Freeman et al. ; Kobak et al.…”