A Chromosome-Level Genome Assembly of the Anglerfish Lophius litulon

A Chromosome-Level Genome Assembly of Yellowtail Kingfish (Seriola lalandi)

Yellowtail kingfish (Seriola lalandi) is a pelagic marine piscivore with a circumglobal distribution. It is particularly suitable for open ocean aquaculture owing to its large body size, fast swimming, rapid growth, and high economic value. A high-precision genome is of great significance for future genetic breeding research and large-scale aquaculture in the open ocean. PacBio, Illumina, and Hi-C data were combined to assemble chromosome-level reference genome with the size of 648.34 Mb (contig N50: 28.52 Mb). 175 contigs was anchored onto 24 chromosomes with lengths ranging from 12.28 to 34.59 Mb, and 99.79% of the whole genome sequence was covered. The BUSCOs of genome and gene were 94.20 and 95.70%, respectively. Gene families associated with adaptive behaviors, such as olfactory receptors and HSP70 gene families, expanded in the genome of S. lalandi. An analysis of selection pressure revealed 652 fast-evolving genes, among which mkxb, popdc2, dlx6, and ifitm5 may be related to rapid growth traits. The data generated in this study provide a valuable resource for understanding the genetic basis of S. lalandi traits.

Genome and gene evolution of seahorse species revealed by the chromosome-level genome of Hippocampus abdominalis

Seahorses belong to the teleost family Syngnathidae that evolved a distinct body plan and unique male pregnancy compared to other teleosts. As a classic model for studying evolution of viviparity and sexual selection of teleosts, seahorse species still lack a publicly available high‐quality reference genome. Here, we generated the genome assembly of the big‐belly seahorse, Hippocampus abdominalis with long‐read and Hi‐C technologies. We managed to place over 99% of the total length of 444.7 Mb of assembled genome into 21 linkage groups with almost no gaps. We reconstructed a phylogenomic tree with the big‐belly seahorse genome and other representative Syngnathidae and teleost species. We also reconstructed the historical population dynamics of four representative Syngnathidae species. We found the gene families that underwent expansion or contraction in the Syngnathidae ancestor were enriched for immune‐related or ion transporter gene ontology terms. Many of these genes were also reported to show a dynamic expression pattern during the pregnancy stages of H. abdominalis. We also identified putative positively selected genes in the Syngnathidae ancestor or in H. abdominalis, whose mouse mutants are enriched for abnormal craniofacial and limb morphological phenotypes. Overall, our study provides an important genome resource for evolutionary and developmental studies of seahorse species, and candidate genes for future experimental works.