Flash flood simulation and valve behavior of Mytilus galloprovincialis measured with Hall sensors

Abstract

Mussels close their shell as a protective strategy and the quantification of this behavioral marker may represent an alarm signal when they are exposed to environmental stressors. In the present study, we investigated the ability of the Mediterranean mussel Mytilus galloprovincialis to recover and then the resilience or inertia of valve activity after a pulsing exposition to diverse levels of salinity (5, 10, 20, and 35 PSU as reference value). The trial simulated an event of drastic and sudden reduction of seawater salinity thus mimicking an event of flash flood from intense rain. Valve gaping and movements were measured in continuous cycle for 10 days using a customized magneto‐electric device which uses Hall sensors. Results showed that under normal conditions of salinity (35 PSU), the general pattern of valve movements was a continuously open state with sporadic spikes indicating a closing motion. At salinity of 5, PSU mussels reacted by closing their valves, leading to a 77% mortality on the 4th day. At salinity of 10, PSU animals were observed with closed valves for the entire duration of the exposure and no mortality occurred, they showed a significant reduction in the valve activity once the reference value of salinity was re‐established. In contrast, salinity of 20 PSU did not trigger a significant behavioral response. Interestingly, there no define rhythms of valve movements were recorded during salinity challenges.

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“…For example, the blue mussel Mytilus edulis only showed a slight reduction in respiration rates when subjected to dissolved oxygen concentrations decreasing from 9 to 2 mg L −1 and demonstrated excellent survival (98%) when exposed to 2 mg L −1 for 16 days [75]. Mytilids also contain a robust mechanism to cope with these stressors, which involves isolating their living tissue through valve closure [7,76]. For example, the valves of M. galloprovincialis have been shown to close in response to declining salinities (~10) and hypoxic conditions [75,76].…”

“…Mytilids also contain a robust mechanism to cope with these stressors, which involves isolating their living tissue through valve closure [7,76]. For example, the valves of M. galloprovincialis have been shown to close in response to declining salinities (~10) and hypoxic conditions [75,76]. During valve closure, however, oxygen concentrations in the mantle cavity can decline rapidly, resulting in a switch to anaerobic respiration [77].…”

“…During valve closure, however, oxygen concentrations in the mantle cavity can decline rapidly, resulting in a switch to anaerobic respiration [77]. Although this metabolic pathway still yields adequate amounts of ATP and glycogen stores [78,79], prolonged closure can result in substantial mortality [76]. For example, exposing M. galloprovincialis to a salinity of 5, thus inducing valve closure, resulted in 77% mortality after ~4 days [76].…”

“…Although this metabolic pathway still yields adequate amounts of ATP and glycogen stores [78,79], prolonged closure can result in substantial mortality [76]. For example, exposing M. galloprovincialis to a salinity of 5, thus inducing valve closure, resulted in 77% mortality after ~4 days [76]. It was thus relevant that dissolved oxygen concentrations during 2021 dropped below 2 mg L −1 for several weeks, conditions that are also considered lethal for most benthic invertebrates [80,81].…”