Extensive gene loss parallels kidney aglomerulism in Syngnathidae

The eccentric seahorses, seadragons, pipehorses and pipefishes (Syngnathidae) have an aglomerular kidney1. Here, we show that nephron genes2 conserved in Bilateria are secondarily eroded/deleted in Syngnathidae genomes. A transcriptome enrichment analysis suggests the predominance of excretion processes in the Syngnathidae kidney. In a lineage where crypsis and idleness are tightly associated, we propose that aglomerulism evolved as an energy-saving strategy.