A chromosome-level genome of electric catfish ( Malapterurus electricus ) provided new insights into order Siluriformes evolution

The electric catfish ( Malapterurus electricus ), belonging to the family Malapteruridae, order Siluriformes (Actinopterygii: Ostariophysi), is one of the six branches that has independently evolved electrical organs. We assembled a 796.75 Mb M. electricus genome and anchored 88.72% sequences into 28 chromosomes. Gene family analysis revealed 295 expanded gene families that were enriched on functions related to glutamate receptors. Convergent evolutionary analyses of electric organs among different lineage of electric fishes further revealed that the coding gene of rho guanine nucleotide exchange factor 4-like ( arhgef4 ), which is associated with G-protein coupled receptor (GPCR) signaling pathway, underwent adaptive parallel evolution. Gene identification suggests visual degradation in catfishes, and an important role for taste in environmental adaptation. Our findings fill in the genomic data for a branch of electric fish and provide a relevant genetic basis for the adaptive evolution of Siluriformes.