Transcriptomic Analysis of Eggs, Rediae and Cercariae Reveal Stage-Specific Adaptations in the Rumen Fluke Calicophoron Daubneyi

Rumen flukes, particularly the trematode Calicophoron daubneyi, are emerging parasites of livestock in Europe, yet transcriptomic insights into their environmental and intermediate host stages remain limited. Here, we present a comprehensive transcriptomic analysis of eggs at three distinct developmental stages (freshly excreted, early developmental and eye-spot stages), as well as rediae and cercariae, of C. daubneyi. High-quality RNA-sequencing (RNA-seq) datasets revealed both shared and stage-specific transcriptional profiles with each developmental stage exhibiting its own distinct expression pattern. Subsequent GO-Term enrichment analyses revealed that fully embryonated eggs in eye-spot-stage especially upregulated genes related to cilia assembly, movement and motility, reflecting preparation for miracidial hatching and host-seeking behavior. Rediae showed enhanced transcription of genes involved in diverse metabolic and biosynthetic processes, supporting rapid asexual proliferation within the snail intermediate host. Cercariae exhibited predominant upregulation of genes associated with signal transduction and energy metabolism, indicating the adaptation to its changing environmental conditions. These findings provide the first transcriptomic insights into the biology of C. daubneyi outside the definitive host, reveal molecular mechanisms underlying development, transmission and adaptation to a changing environment and identify stage-specific genes as potential targets for interventions aimed at disrupting the parasites life cycle and controlling rumen flukes in the future.