Heat shock protein responses to salinity, food deprivation, and temperature in the invasive ground beetle Merizodus soledadinus at the Kerguelen Islands

The ground beetle Merizodus soledadinus was introduced a century ago to the Kerguelen Islands. It has since become invasive and has colonized most coastlines east of this archipelago. In invaded intertidal zones, M. soledadinus has to deal with substrates that can reach high salinity levels. In addition to saline stress, the rapid spread of this invasive insect on the Kerguelen Islands may result in starving during dispersal, especially during winter periods. In order to gain a further understanding of the factors that have contributed to the success of this insect in invading the Kerguelen Islands, we assessed the variability in the expression of heat shock cognate 70 (HSC70) in M. soledadinus. HSC70 are constitutively expressed by insects, and we examined if the expression of HSC70 could picture the health degree of the ground beetles exposed at a range of environmental conditions, for example, varying temperatures (0, 4, 8, 12, and 20 °C), trophic status (fed and food-deprived individuals), and saline conditions (salinities of 0, 35, and 70). We found that HSC70 expression decreased with increasing salinity. HSC70 expression was not modified in response to non-extreme thermal variations or short-term food deprivation, which did not appear to be stressful conditions for M. soledadinus given the survival results. We concluded that HSC70 expression may serve as a molecular indicator of the levels of well-being of this ground beetle when exposed to a range of environmental perturbations.