Author Correction: Opah ( Lampris megalopsis) genome sheds light on the evolution of aquatic endothermy.

Endothermy is the ability to generate and conserve metabolic heat to maintain body temperature above that of the surrounding environment. Endothermy enhances the physiological and ecological advantages of mammals, birds, and certain fish species. The opah, Lampris megalopsis (Lampridiformes), is the only known fish to exhibit whole-body endothermy. Currently, however, the underlying molecular mechanism for this remains unclear. Hence, the opah offers an excellent opportunity to study the evolutionary mechanism of whole-body endothermy in aquatic animals. In this study, we assembled a L. megalopsis genome (1.09 Gb in size) and performed comparative genomic analysis with ectothermic fish to reveal the genetic basis of endothermy. Based on analysis of positive selection, rapid evolution, and gene family expansion, we discovered several genes that likely contributed to thermogenesis and heat preservation. As the first reported L. megalopsis genome, our results not only clarify the possible molecular and genetic mechanisms involved in endothermic adaptation but also increase our understanding of endothermic fish biology. Fish face a massive challenge in maintaining body temperature due to the high thermal conductivity of water, with fewer than 0.1% of fish species able to retain internally produced heat. Endothermic fish exhibit strong swimming efficiency, enhanced cold tolerance, high visual acuity for vertical migration, and competitive advantages in predatorprey interactions and niche expansion (Wegner et al., 2015). Recently, the opah (L. guttatus) was discovered to show whole-body endothermy, which is thought to be unique among fish. Globally distributed opahs were originally described as Lampris guttatus (Brünnich, 1 788), but have since been divided into L. incognitus, L. australensis, L. megalopsis, L. guttatus, and L. lauta based on geographical distribution and morphology (Hyde et al., 2014; Underkoffler et al., 2018). The opahs have two thermogenic strategies. They use metabolization of pectoral muscles to generate heat, and they use a specialized intracranial thermogenesis tissue to generate heat. In addition, the opahs have two heat conservation strategies. An extensive of retia mirabilia in intracranial and gill is used for insulation. And thick adipose tissue is another strategy for heat conservation (Franck et al., 2019; Runcie et al., 2009; Wegner et al., 2015). In the current study, an opah specimen was collected from the southern Indian Ocean onboard the Chinese tuna longline vessel “PING TAI RONG 65” and was transported to Zhoushan, China, on 12 September 2018, by “PING TAI RONG LENG 2” for dissection and muscle extraction (Supplementary Figure S1). Mitochondrial genes (cytochrome c oxidase I (COI) and cytochrome b (cyt b)) identified the specimen as a bigeye pacific opah (L. megalopsis) (Supplementary Figures S2, S3), which is known to be distributed in the southern Indian Ocean (Underkoffler et al., 2018). We assembled a L. megalopsis genome (1 091 Mb), which consisted of 12 081 contigs, with a contig N50 of 590 kb and N90 of 30 kb (Supplementary Table S1). Compared with 38.8% for the previously released L. guttatus genome (ASM90030254v1), BUSCO assessment of single-copy orthologs showed that the completeness of our genome was 90.5%, indicating high-quality assembly. A total of <number>23755</number> genes were annotated in the opah genome. We constructed a phylogenetic tree with all singlecopy genes (Figure 1A). Among 13 ectothermic fish, opah was closest to the zebrafish, with an estimated divergence time of ~216 million years ago (Ma). The opah uses its dark red aerobic pectoral muscles for continuous swimming and metabolic heat production. On average, the muscle has a temperature that is 4.8±1.2 °C