Functional chimeric genes in ciliates: An instructive case from Euplotes raikovi

•Chimeric genes are generated by ciliates during the macronuclear development.•In Euplotes raikovi, a pheromone-coding gene, mac-er-1, coexists with a chimeric copy, mac-er-1*.•mac-er-1* originates from the mac-er-1 assembly with an extraneous sequence.•mac-er-1* is functional and practically duplicates the mac-er-1 activity.