Heart oedema in freshly hatched larvae of Eurasian perch is associated with multi-tissue gene dysregulation

Deformities in newly hatched Eurasian perch ( Perca fluviatilis ) larvae poses a significant challenge in aquaculture, impacting larval quality, survival and overall production success. This study investigates the molecular basis of a specific deformity, heart oedema, through whole-body transcriptomic analysis comparing deformed to morphologically normal larvae. Differential gene expression (DEG) analysis identified key candidate genes implicated in glucose metabolism ( gck ), oxygen transport ( hbz ), cardiac development and regulation ( nppa, flnc ), and vascular integrity ( arl14 ). Additional DEGs were linked to functions in non-cardiac tissues, suggesting a broader systemic response to the heart oedema deformity. Notably, results indicate gamete-derived factors influence early developmental outcomes, even under controlled environmental and similar genetic background. These findings highlight the complexity of embryonic development and shed light on molecular pathways associated with spontaneous cardiac deformities, providing a foundation for future studies to validate early biomarkers of developmental abnormalities. • Cardiac oedema is a lethal larval deformity in cultured fishes. • RNA-seq identified 16 heart-specific genes altered in heart oedematose larvae. • Validated genes involve glucose metabolism, oxygen transport, heart structure. • Findings suggest that gamete molecular heterogeneity shape early cardiac development. • Results offer potential biomarkers for lethal larval heart deformities.