Behavior and survival ofMytiluscongeners following episodes of elevated body temperature in air and seawater

Abstract

Summary Coping with environmental stress may involve combinations of behavioral and physiological responses. We examined potential interactions between adult mussels’ simple behavioral repertoire – opening/closing of the shell valves – and thermal stress physiology in common-gardened individuals of three Mytilus congeners found on the West Coast of North America, two of which are native species (M. californianus and M. trossulus) and one an invasive from the Mediterranean (M. galloprovincialis). We first continuously monitored valve behavior over three consecutive days on which body temperatures were gradually increased, either in air or in seawater. A temperature threshold effect was evident between 25°C and 33°C in several behavioral measures. Mussels tended to spend much less time with the valves in a sealed position following exposure to 33°C body temperature, especially when exposed in air. This behavior could not be explained by decreases in adductor muscle glycogen (stores of this metabolic fuel actually increased in some scenarios), impacts of forced valve sealing on long-term survival (none observed in a second experiment), or loss of contractile function in the adductor muscles (individuals exhibited as many or more valve adduction movements following elevated body temperature as in controls). We hypothesize that this reduced propensity to seal the valves following thermal extremes represents avoidance of hypoxia-reoxygenation cycles and concomitant oxidative stress. We further conjecture that prolonged valve gaping following episodes of elevated body temperature may have important ecological consequences by affecting species interactions. We then examined survival over a 90-d period following exposure to elevated body temperature and/or emersion, observing ongoing mortality throughout this monitoring period. Survival varied significantly among species (M. trossulus had lowest survival) and among experimental contexts (survival was lowest after experiencing elevated body temperature in seawater). Surprisingly, we observed no cumulative impact on survival of three days relative to one day of exposure to elevated body temperature. The delayed mortality and context-specific outcomes we observed have important implications for design of future experiments and for interpretation of field distribution patterns of these species. Ultimately, variation in the catalog of physiological and behavioral capacities among closely related or sympatric species is likely to complicate prediction of the ecological consequences of global change and species invasions.

Thermal variation, thermal extremes and the physiological performance of individuals

“…Petes et al, 2007) or even death (e.g. Dowd and Somero, 2013). In short, an individual's response to the variation in the timing, intensity, duration and interval between stressful events can alter its performance.…”

Thermal stress increases fluctuating asymmetry in marine mussels: environmental variation and developmental instability

“…v www.esajournals.org 1971, Schneider et al 2010, Place et al 2012, Dowd and Somero 2013, their impact on developmental stability remains unclear. It is predicted that warmer temperatures may disrupt developmental stability and increase FA between left and right shell valves (e.g., increased width of distributions; Fig.…”

Effect of temperature on behavior, glycogen content, and mortality in Limnoperna fortunei (Dunker, 1857) (Bivalvia: Mytilidae)

“…Thermal stress in bivalves may cause combinations of behavioral (valve closing/opening) and physiological responses (Anestis et al, 2007;Dowd and Somero, 2013). In the present work, the effects of thermal stress were assessed in terms of valve closing, glycogen concentration in the tissues and mortality.…”

“…The metabolic activities of mussels usually increase with higher temperatures, and oxygen and food resources can become scarce with increasing water temperature (Carey et al, 2013). Thus, as a consequence of environmental fluctuations and other stressors, marine and freshwater mussels have developed a physiological and behavioral strategy (i.e., valve closing) necessary for survival in several waterbodies (Kittner and Riisgård, 2005;Palais et al, 2011;Dowd and Somero, 2013).…”

“…This phenomenon deserves attention in future research. This change in glycogen concentration and behavior may be related to physiological perturbation during this period elicited by stress (Dowd and Somero, 2013). In this case, the maintenance of glycogen concentrations and the valve closing behavior at the end of the experiment are considered to be indicative of an adaptation to stress conditions (Widdows and Bayne, 1971).…”