Heat Stress and Anthropogenic Substrates: Molecular and Behavioral Adaptation of Metridium senile in Human-Modified Marine Environments

Marine litter provides novel habitats for substrate-dependent species, potentially facilitating their expansion under climate change. This study investigated the thermal adaptability and substrate selectivity of the cold-water sea anemone Metridium senile in the Yellow Sea, where rising temperatures and anthropogenic substrates may drive its proliferation. Behavioral experiments revealed diminished adhesion capacity under thermal stress (13 °C and 18 °C), with no substrate preference observed. Transcriptomic analysis identified 175 and 340 differentially expressed genes (DEGs) at 13 °C and 18 °C, respectively, compared with the control (8 °C). These DEGs were enriched in metabolic processes, oxidative stress, and cell homeostasis, with key pathways including dorso-ventral axis formation, ECM–receptor interaction, TGF-β, and Wnt signaling pathways. Notably, 7 regeneration-related, 20 adhesion-related, and 16 collagen-related DEGs were implicated in adaptive responses to heat stress. Our findings elucidate the molecular mechanisms underlying M. senile’s resilience and highlight its potential to exploit human-modified habitats under warming conditions, offering insights into ecological shifts in marine ecosystems.