The sperm RNA payload in fishes: A vector for paternal inheritance and memory

Paternal RNAs are involved in the phenotype of progeny that may be transmitted across generations. In fishes, sperm RNAs have been identified, however their sources and biological functions remain largely unknown. In this review, we highlight that sperm RNAs are the remnants of spermatogenesis or are obtained from extracellular vesicles in the sperm duct during maturation. Therefore, multiple factors can influence the sperm RNAs profiles by modulating these processes. Sperm RNAs are transferred to embryos at fertilization, resulting in the reestablishment of paternally acquired traits in offspring. This suggests a role for sperm RNAs in mediating RNA-dependent paternal inheritance across generations. These underlying mechanisms involve the modulation of gene cascades in the embryos or the reshaping of chromatin to different conformations. This review addresses current knowledge gaps regarding the regulatory mechanisms underlying RNAs biogenesis and modification in fish sperm. It suggests that further investigations are needed to elucidate the functional consequences of RNAs profiles and their modifications that contribute to paternal effects on offspring phenotypes, providing aquaculture, fisheries, and conservation with invaluable information. • Spermatozoa are capable of de novo transcription and translation • Fish spermatozoa RNAs are derived from both intracellular and extracellular sources • Fish sperm RNAs profiles are affected by diverse biotic and abiotic factors • Paternal traits can be transmitted to offspring by an RNA-mediated mechanism