Jacobs, A.; Decanter, N.; Torresen, O. K.; Garmann-Aarhus, B.; Capstick, M.; Rougemont, Q.; Guillaume, F.; Normand, R.; Tremblay, J.; Destouches, J.-P.; Besnard, A.-L.; Souissi, A.; Lassalle, G.; Stoeckel, S.; Petit, E.; Hoff, S. N. K.; Park, D.; Pope, B.; Jentoft, S.; Vollestad, L. A.; Jakobsen, K. S.; Evanno, G.

Lampreys are the only ancestrally parasitic vertebrate lineage, yet parasitism has been repeatedly lost alongside a suite of life-history changes, such as loss of migration and juvenile feeding and accelerated maturation. Combining whole-genome resequencing, haplotype-resolved assemblies, hybrid-zone genotyping, multi-tissue transcriptomics, and sperm phenotyping, we map this life-history syndrome in European Lampetra to six chromosomes spanning a mosaic of genomic architectures: a ~20 Mb low-recombination region on chromosome 1 lacking chromosomal rearrangements within Lampetra but involving inter-specific rearrangements across deep lamprey lineages; a translocated inversion with ecotype-dependent sperm-velocity effects; and ecotype-divergent deletions overlapping genes crucial for nervous system (CNTNAP2) and reproductive development (FSHR). However, this genomic basis is not shared with a convergent sister lineage, pointing to independent routes to a recurring life-history transition in lampreys.