Most animals exhibit bilat­eral symme­try, but asymmet­ric traits have repeat­edly evolved in differ­ent taxonomic groups. However, the genetic mecha­nisms respon­si­ble for asymmet­ric trait varia­tion remain unclear. We will use the scale-eating fish, Peris­so­dus microlepis, to dissect the genetic basis of its remark­able morpho­log­i­cal and behav­ioural asymme­try. This study will yield impor­tant insights into the mecha­nis­tic under­pin­nings of asymmet­ric devel­op­ment and the origin of evolu­tion­ary novelty.

While most verte­brates exhibit a bilat­er­ally symmet­ric body plan, cases of asymmet­ric traits have been well documented across the animal kingdom, the most famous example being behav­ioural later­al­ity, “handed­ness,” of humans. However, the origin and mainte­nance of such asymmet­ric varia­tion remain an unresolved question in evolu­tion­ary biology.

The scale-eating cichlid fish, Peris­so­dus microlepis, from Lake Tanganyika is a remark­able example of morpho­log­i­cal and behav­iour asymme­try. Like human handed­ness, this species is charac­ter­ized by later­al­ized forag­ing behav­iours, with some individ­u­als prefer­en­tially feeding on scales from the right side of prey, and others from the left. This behav­ioural later­al­ity is coupled with asymmet­ric head morphol­ogy that facil­i­tates feeding on scales from the preferred side. The abundance of individ­u­als with left or right later­al­ity has been shown to fluctu­ate around 50% over long time periods, making this species a textbook example for the mainte­nance of varia­tion in nature. However, the molec­u­lar mecha­nisms under­ly­ing this morpho­log­i­cal and behav­ioural asymme­try remain elusive.

This project will inves­ti­gate the genetic basis of head asymme­try and lateral forag­ing behav­iour in this system. By combin­ing high resolu­tion pheno­typ­ing methods (micro-CT analy­ses) with forward genetic approaches and exper­i­men­tal manip­u­la­tion, we will reveal the genetic and environ­men­tal mecha­nisms control­ling this textbook example for a stable polymor­phism of asymmetry.