Attachment strength of the mussel Mytilus galloprovincialis: Effect of habitat and body size

Abstract

13Marine organisms adapt to a wide variety of environments, often altering their morphology and behaviour in 14 response to local habitat. This study addressed the effects of habitat (wave exposure) and body size on the 15 morphology and byssal attachment of mussels within the same estuary. Tenacity of the mussel Mytilus 16 galloprovincialis was higher at the exposed site, particularly for the smaller size classes. This was largely 17 due to differences in thread thickness; mussels from the exposed site produced thicker and stronger byssal 18 threads. For a given shell length, exposed mussels also produced thicker and smaller shells and had lower 19 gonadal condition. In laboratory flume experiments, both thread production and mechanical performance 20 (strength and extensibility) decreased with increased flow, suggesting flow alone does not explain tenacity 21 differences between sites. Altogether, these analyses suggest that mussels at exposed sites allocate resources 22 to reducing risk of dislodgment (smaller and thicker shell, stronger byssal threads) instead of growth and 23 reproduction, and these allocation differences between sites are less apparent in larger size classes. The lack 24 2 of the largest size class (8 cm) at the exposed site may reflect an upper limit to size imposed by wave 25 induced mortality, where attachment strength does not keep pace with hydrodynamic loading. 26 27 28 Introduction 29

Anti-predatory responses of the thick shell mussel Mytilus coruscus exposed to seawater acidification and hypoxia

“…Some researches indicated aquatic predators were less efficient at capturing prey when oxygen levels were low (McIntyre and McCollum, 2000;Taylor and Eggleston, 2000;Brante and Hughes, 2001). On the contrary, some reports implied that predators could rapidly reinvade the areas after relaxation of hypoxic conditions (Pihl et al, 1991;Nestlerode and Diaz, 1998;Bell and Eggleston, 2005) and increase foraging after a hypoxic episode (Long et al, 2008). Kroeker et al (2014) reported that it is yet unclear whether marine predators actually prefer prey species from acidified conditions or are able to detect a difference between prey from acidified and non-acidified environments.…”

“…When energy supply is limited by environmental stress, byssus thread production has to compete with other physiological processes for energy. For instance, the zebra mussels, Dreissena polymorpha reduce their feeding when they detect their predator (Czarnoleski et al, 2011), and the mussels Mytilus galloprovincialis under wave exposure produce thicker and stronger byssus threads at the cost of lower growth and gonadal condition (Babarro and Carrington, 2013). If energy allocation to byssus thread production remains unchanged under some stressors, i.e., hypoxia and OA, there is a disproportionate decrease in energy supply for other physiological processes.…”

Interspecies comparison of the mechanical properties and biochemical composition of byssal threads

“…This mechanism for avoiding dislodgement, however, comes at a cost. Babarro and Carrington (2013) suggested that mussel populations at wave-exposed habitats invest more energy in the production of protective tissues, such as shells and byssus, than in reproduction and growth. The byssus is a series of threads made of fibrous proteins with outstanding mechanical properties (Waite, 1985).…”

Selective byssus attachment behavior of mytilid mussels from hard- and soft-bottom coastal systems

“…It is known that mussels can adapt their attachment strength by means of increased byssus production (Denny and Gaylord, 2010;Carrington et al, 2015), which depends on mussel size, with small-sized individuals typically producing more byssus threads than large-sized conspecifics (e.g. Babarro and Carrington, 2013). While mussels might also adjust the thickness of byssus in response to hydrodynamic variability (Carrington et al, 2015), they mostly enhance or decrease the number of byssus threads (Carrington et al, 2008;Babarro and Carrington, 2013).…”

“…Babarro and Carrington, 2013). While mussels might also adjust the thickness of byssus in response to hydrodynamic variability (Carrington et al, 2015), they mostly enhance or decrease the number of byssus threads (Carrington et al, 2008;Babarro and Carrington, 2013).…”