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Abstract
Atmospheric heat waves and marine heat waves continue to increase in temperature, frequency, and duration. Intertidal organisms are hypothesized to be particularly vulnerable to acute heat stress, or heat shock, events given their susceptibility to both atmospheric and marine heat waves. Indeed, evidence suggests heat shock can adversely affect intertidal adult metabolism, reproduction and survival. Yet, little is known about how heat shock affects critical developmental stages in intertidal organisms. Previous research on porcelain crabs (Petrolisthes cinctipes), a midintertidal organism, across life stages found significantly higher thermal tolerance in embryos. However, it is unclear to what extent heat shock during different embryonic stages affects physiology. Here, we test the hypothesis that P. cinctipes heat shocked during different embryonic stages affects metabolism, growth, and survival. We applied a 32°C heat shock for one hour on 12 related embryos and five maternal lineages across seven developmental weeks (n = 420) from June to August 2024. We imaged embryos and compared embryo area, yolk consumption, and hatch success of heat shocked individuals to 12 control embryos within each family (n = 60). We expected higher mortality, lower growth, and increased yolk consumption in individuals heat shocked later in embryonic development given the stressful transition from the embryonic to the larval stage. Contrary to our predictions, we found that heat shock does not significantly affect hatch success across families. Additionally, we found heat shock did not affect yolk consumption and growth compared to within family controls. However, when we observe maternal lineage, we find significant differences in yolk consumption and growth among families. Our results suggest that maternal effects act as the primary factor in embryonic yolk consumption and growth variability, and heat shock week does not play a role. Further research into genetic differences and transgenerational plasticity is necessary to fully understand how P. cinctipes embryos respond to acute thermal stress.