Ostariophysan fishes consist of almost 28% of all known fish species and 68% of the world's freshwater fishes, which are the largest and most diverse group of primarily freshwater fishes. How ostariophysan fishes diversified in freshwater environments is unclear.   

Recently, Professor HE Shunping and his team from Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences in Wuhan, together with international collaborators from Yale University, examined the reservoir of vomeronasal receptor genes (OlfC) and found an obvious relationship between the evolution of OlfC genes with the diversification of ostariophysan fishes. The results were published in Communications Biology.   

The study analyzed a total of 13 fish genomes, including five ostariophysan fishes having fright reaction, two ostariophysan fishes lacking fright reaction, and six non-ostariophysan fishes. Study results showed that ostariophysan fishes having fright reaction have significantly large number of OlfC genes than fishes lacking fright reaction. They built a phylogenetic tree to show the specifically expansion of OlfC subfamily 9 in ostariophysan fishes. Expression levels of expanded OlfC subfamily genes after fright reaction in zebrafish changed more than that of genes that had not expanded. 

This is the first time to investigate the genetic basis of diversification for ostariophysan fishes, and has important impact to link phenotype and genotype. 

Expansion of OlfC genes in ostariophysan fishes (Figure by IHB)