Background Betanodaviruses, members of the Nodaviridae family, are the causative agents of viral nervous necrosis in fish, resulting in great economic losses worldwide. Methods In this study, we isolated a virus strain named seahorse nervous necrosis virus (SHNNV) from cultured big-belly seahorses Hippocampus abdominalis in Xiamen city, Fujian Province, China. Virus isolation, PCR detection, phylogenetic analysis, qRT-PCR, fluorescence in situ hybridization and histology were used for virus identification and analysis of virus histopathology. Furthermore, an artificial infection experiment was conducted for virulence testing. Results Brain and eye tissue homogenates of diseased big-belly seahorses were inoculated onto a grouper spleen (GS) cell monolayer at 28 °C. Tissue homogenates induced obvious cytopathic effects in GS cells. PCR and sequencing analyses revealed that the virus belonged to Betanodavirus and shared high sequence identity with red-spotted grouper nervous necrosis virus isolates. qRT-PCR and fluorescence in situ hybridization revealed that SHNNV mainly attacked the brain and eye. Histopathological examination revealed that the virus led to cytoplasmic vacuolation in the brain and retinal tissues. Infection experiments confirmed that SHNNV was highly infectious, causing massive death in big-belly seahorses. Conclusion A novel seahorse betanodavirus from the big-belly seahorse cultured in China was discovered. This finding will contribute to the development of efficient strategies for disease management in aquaculture.

In this study, we determined the complete mitochondrial genome of the Picasso panda clownfish for the first time. The length of the whole mitogenome is 16,652 bp long and contained 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, 2 non-coding regions and 1 control region(D-lop). The mitochondrial genome of the Picasso panda clownfish consisted of A = 29.19%, T = 25.49%, G = 15.93% and C = 29.40% (AT-skew = 0.067 and GC-skew = −0.297). Molecular phylogenetic analysis suggested that Amphiprion ocellaris, Amphiprion percula, Premnas biaculeatus and the Picasso panda clownfish clustered in one branch of the phylogenetic tree. Picasso panda clownfishand and A. ocellaris are most closely related.