A preliminary whole-genome survey of longfin snake eel Pisodonophis cancrivorus (Richardson, 1848)

Longfin snake eel, Pisodonophis cancrivorus (Anguilliformes: Ophichthidae), is a typical snake eel widely distributed across brackish and marine waters of the Indo-Pacific oceans. As sensitivity to environmental change, it has become a potential bio-indicator for assessing habitat health in tropical coastal ecosystems, and plays a significant ecological role in nutrient cycling and benthic community dynamics. However, to our knowledge, no related genomic studies of P. cancrivorus have been reported until now. In this study, the preliminary genome information of P. cancrivorus was derived by using a whole-genome survey method. The genome size was estimated at 2.01 Gb, with the heterozygosity, repetitive sequence ratio and GC content of 1.35%, 39.37% and 41.56%, respectively. A total of 4,338,707 genome-wide microsatellites were mined, with the occurrence frequency of 27.13%. Among six perfect microsatellites, dinucleotide repeats were most abundant (42.23%), whereas pentanucleotide repeats had the lowest proportion (1.33%). About 5,539 putative coding genes were identified in total. By functional classification using Gene Ontology (GO) and EuKaryotic Orthologous Groups (KOG) databases, these annotated genes involved in many physiological and biochemical processes including cellular process, cellular anatomical entity, binding and signal transduction mechanisms. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed neuroactive ligand-receptor interaction was among the most frequently annotated KEGG pathways. The reconstructed phylogenomic relationships indicated that P. cancrivorus, Conger conger and C. myriaster cluster into the same branch in the evolutionary tree. The topology preliminarily supported a close relationship between Ophichthidae and Congridae, while the two sampled Muraenidae species formed a separate clade. This study provides the latest genomic resource and a preliminary phylogenomic reference for this Ophichthidae species.