Stress-on-stress responses of a marine mussel, Perna canaliculus: food limitation reduces the ability to cope with heat stress in juveniles

Abstract

The marine environment is ever-changing, with daily and seasonal variations in factors such as food availability and seawater temperature. These stressors can affect physiological processes in aquatic organisms, resulting in sub-lethal or lethal consequences. This study assessed the effects of food limitation (i.e. fasting) on heat-stress responses in juveniles (~1.3 mm in shell length) of the green-lipped mussel Perna canaliculus. Fasting for up to 24 h did not have a significant effect on oxidative damage (protein carbonyls and lipid hydroperoxide accumulation) or the activity of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase) after exposure to heat stress. However, fasting for 54 h and subsequent heat stress resulted in increased oxidative damage and decreased activity of antioxidant enzymes in juvenile mussels. Gene expression of 70 kDa heat shock protein (hsp70) was only significantly affected by heat shock, not nutritional status. Tissue carbohydrate and protein levels were significantly depleted by 54 h of fasting; as these proximate components represent key energy substrates for bivalves, it is suggested that energy limitation contributes to compromised antioxidant activity and predisposition to oxidative damage.

Emersion and Relative Humidity Modulate Stress Response and Recovery Dynamics in Juvenile Mussels (Perna canaliculus)

“…The emersion times used in this study are representative of a typical exposure period for an intertidal P. canaliculus (1 h), an exceptional low tide event (5 h), and an artificial emersion time which would represent a common transport time for mussel spat from hatchery to the grow-out farms (20 h). It should be noted that the juvenile mussels used in this study are hatchery produced from subtidal mussel populations (farmed); the results shown here might vary from the potential stress response of wild spat which may have previously experienced emersion [ 36 ] and associated stressors, with the potential to either increase [ 37 ] or reduce [ 32 ] subsequent stress tolerance.…”

“…Macromolecule extractions (protein, lipid and DNA) for determination of oxidative damage in juvenile P. canaliculus were performed according to Delorme et al [ 32 ] In brief, total protein was extracted on ice by adding 900 µL of ice-cold enzyme extraction buffer (100 mM potassium phosphate [pH 7.5] containing 50 mM NaCl, 0.1 mM Na2EDTA, 1% polyvinylpyrrolidone−40, 2 mM phenylmethylsulfonyl fluoride and 0.1% TritonX−100) and homogenising for 30 s at 1500 rpm (1600 MiniG ® , SPEX ® ) using zirconia/silica beads and a pre-chilled cryo-block (SPEX ® ). The samples were then centrifuged for 15 min at 17,000× g at 4 °C and the supernatant (i.e., protein extract) purified using ultrafiltration and purification columns (AMICON).…”

“…The remaining protein extract was used to perform antioxidant enzyme assays: superoxide dismutase activity (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) as described by Delorme et al [32] In brief, SOD was determined using a Cayman Chemicals Superoxide Dismutase Assay Kit and the activity expressed as units of SOD mg of protein −1 . CAT was assayed using the chemiluminescent method of Maral et al [63], as adapted by Janssens et al [64] for 96-well microplates, and the activity expressed as µmol min −1 mg protein −1 .…”

“…The mussel industry routinely transfers juvenile mussels from their capture sites or from its single hatchery to marine farms around the country, a process that can involve emersion of up to 72 h [29,31]. Previous studies have described the stress response of P. canaliculus juveniles and adults to fasting, heat and simulated transport, showing that fasted juveniles are less able to tolerate subsequent stress, and that transport results in oxidative damage [32][33][34]. Additionally, variations in RH during emersion can affect the resettlement behaviour of juvenile P. canaliculus during recovery in seawater, although the underlying dynamic of physiological responses of these stressed juveniles remains unknown [28].…”

Observations on recent mass mortality events of marine mussels in the Oosterschelde, the Netherlands

“…The cumulation of adverse environmental conditions can weaken mussels and make them more susceptible to mortality from conditions that they are able to cope with under normal circumstances (Delorme et al 2020). This is also dependent on the health status of the mussel.…”