Differences in heat shock protein 70 expression during larval and early spat development in the Eastern oyster, Crassostrea virginica (Gmelin, 1791)

For a variety of species, changes in the expression of heat shock proteins (HSP) have been linked to key developmental changes, i.e., gametogenesis, embryogenesis, and metamorphosis. Many marine invertebrates are known to have a biphasic life cycle where pelagic larvae go through settlement and metamorphosis as they transition to the benthic life stage. A series of experiments were run to examine the expression of heat shock protein 70 (HSP 70) during larval and early spat (initial benthic phase) development in the Eastern oyster, Crassostrea virginica. In addition, the impact of thermal stress on HSP 70 expression during these early stages was studied. C. virginica larvae and spat expressed three HSP 70 isoforms, two constitutive, HSC 77 and HSC 72, and one inducible, HSP 69. We found differences in the expression of both the constitutive and inducible forms of HSP 70 among larval and early juvenile stages and in response to thermal stress. Low expression of HSP 69 during early larval and spat development may be associated with the susceptibility of these stages to environmental stress. Although developmental regulation of HSP 70 expression has been widely recognized, changes in its expression during settlement and metamorphosis of marine invertebrates are still unknown. The results of the current study demonstrated a reduction of HSP 70 expression during settlement and metamorphosis in the Eastern oyster, C. virginica.     

Laboratory simulation of a mining accident: acute toxicity, hsc/hsp70 response, and recovery from stress in Gammarus fossarum (Crustacea, Amphipoda) exposed to a pulse of cadmium

The rate of survival and stress protein (hsc/hsp70) response were investigated in the freshwater amphipod, Gammarus fossarum Koch, 1835, during a 20-day stress and recovery experiment. Adult females and males, were separately exposed to 9 different cadmium concentrations for 5 days to simulate a short-term pulse of xenobiotics in an aquatic environment, followed by a recovery period of 15 days. In terms of mortality, females were much more sensitive to cadmium than males; 4.28±2.45 g Cd²⁺/l resulted in strong effects on the rate of survival of females but not males. In both sexes, mortality occurred predominantly within the first 5 days of the recovery period. At the cellular level, cadmium induced an hsc/hsp70 response. The lower Cd²⁺ concentrations we used led to an induction of stress proteins while higher Cd²⁺ concentrations resulted in a proportionately reduced hsc/hsp70 response, most likely due to pathological damage. Surviving individuals retained their capacity to induce stress protein production in the recovery period, even if the stress protein response system was overwhelmed by cadmium during the exposure period.     

Daily and seasonal changes in heat exposure and the Hsp70 level of individuals from a field population of Xeropicta derbentina (Krynicki 1836) (Pulmonata, Hygromiidae) in Southern France

The Mediterranean land snail Xeropicta derbentina forms huge populations in Southern France. In order to characterize heat exposure and the induction of the 70-kD heat shock protein (Hsp70) response system during the life cycle of this snail, a selected population from the Vaucluse area, Provence, was investigated encompassing the issues of morphological life cycle parameters (shell size and colouration), the daily courses of heat exposure at different heights above the ground, of shell temperature, and that of the individual Hsp70 levels. The study covered all four seasons of the year 2011. Snails were found to be annual, reaching their final size in August. The shell colouration pattern showed high variation in juveniles (spring) with a strong tendency towards becoming uniformly white at old age in autumn. In all seasons, ambient air temperature decreased with increasing distance from the ground surface during daytime while remaining constantly low in the night. Overall, the Hsp70 level of individuals followed the ambient temperature during diurnal and seasonal variations. Correlation analysis revealed a positive association of individual shell temperature and Hsp70 level for the most part of the life cycle of the snails until late summer, whereas a negative correlation was found for aged animals indicating senescence effects on the capacity of the stress response system.