Comparative Genomics Reveals Autophagy‐Lysosome Pathway Expansion and Adaptive Gene Selection in Anguillid Eels

Anguillid eels have a catadromous life cycle, transitioning from deep‐sea larvae to adults in estuaries and freshwater environments. It is well‐established that adult eels cease feeding and experience gut degeneration during their spawning migration. However, the evolutionary mechanisms behind the removal and recycling of damaged tissues in eels during this process remain unclear. This study aims to identify the genes that may play a role in the adaptation of Anguillid eels to their unique, once‐in‐a‐lifetime deep‐sea migration. To investigate these mechanisms, we conducted a comparative genomic analysis using high‐quality genomes from four Anguillid eels. We specifically examined genes that exhibited significant expansion or were subject to positive selection. Among the expanded gene families in four eel species, we observed notable enrichment in the endocytosis pathway ( p < 0.05). Additionally, using the branch‐site model, we detected 65 positively selected genes (PSGs) in the Anguillid eel branch ( p < 0.05). Interestingly, we found PSGs are associated with autophagy‐lysosome pathways (ALPs), suggesting their role in energy production during periods of nutrient scarcity. This study provides valuable insights into the adaptive mechanisms of Anguillid eels, enhancing our understanding of their survival strategies during migration, despite their being in a nonfeeding state.