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Abyssal (3501–6500 m) and hadal (>6500 m) fauna evolve under harsh abiotic stresses, characterized by high hydrostatic pressure, darkness and food shortage, providing unique opportunities to investigate mechanisms underlying environmental adaptation. Genomes of several hadal species have recently been reported. However, the genetic adaptation of deep sea species across a broad spectrum of ocean depths has yet to be thoroughly investigated, due to the challenges imposed by collecting the deep sea species. To elucidate the correlation between genetic innovation and vertical distribution, we generated a chromosome‐level genome assembly of the macrourids Coryphaenoides yaquinae, which is widely distributed in the abyssal/hadal zone ranging from 3655 to 7259 m in depth. Genomic comparisons among shallow, abyssal and hadal‐living species identified idiosyncratic and convergent genetic alterations underlying the extraordinary adaptations of deep‐sea species including light perception, circadian regulation, hydrostatic pressure and hunger tolerance. The deep‐sea fishes (Coryphaenoides Sp. and Pseudoliparis swirei) venturing into various ocean depths independently have undergone convergent amino acid substitutions in multiple proteins such as rhodopsin 1, pancreatic and duodenal homeobox 1 and melanocortin 4 receptor which are known or verified in zebrafish to be related with vision adaptation and energy expenditure. Convergent evolution events were also identified in heat shock protein 90 beta family member 1 and valosin‐containing protein genes known to be related to hydrostatic pressure adaptation specifically in fishes found around the hadal range. The uncovering of the molecular convergence among the deep‐sea species shed new light on the common genetic innovations required for deep‐sea adaptation by the fishes. [ABSTRACT FROM AUTHOR]

Alicella gigantea, the largest amphipod scavengers found to date, play key roles in the food web of the hadal ecosystem. However, the genetic structure of A. gigantea populations among different trenches has not been reported yet. In this study, SNP (single-nucleotide polymorphism) markers were developed for three A. gigantea geographic populations collected from the southern Mariana Trench (SMT), the central New Britain Trench (CNBT), and the eastern New Britain Trench (ENBT), based on the SLAF-seq (specific locus amplified fragment sequencing) technology. A total of 570,168 filtered SNPs were screened out for subsequent population genetic analysis. Results showed that the inbreeding levels across the three geographic populations were relatively low, and the genomic inbreeding coefficients of the three populations were similar in magnitude. Based on the results of phylogenetic analysis, population structure analysis, and principal component analysis, it is believed that the three A. gigantea geographic populations belong to the same population, and the kinship relationship between the ENBT and CNBT populations is close. Moreover, the differential candidate adaptive sites on the SNPs suggest that there may be variations in metabolic rates among the three geographic populations, possibly linked to differences in food availability and sources in different trenches, ultimately resulting in different survival strategies in A. gigantea populations within distinct trenches. Compared with the Mariana Trench, the New Britain Trench has a richer organic matter input, and it is speculated that the A. gigantea Mariana Trench population may adopt a lower metabolic rate to cope with the harsher environment of nutrient deficiency. [ABSTRACT FROM AUTHOR]

ABSTRACT The swimming crab Portunus trituberculatus is an important fishery and aquaculture species in China, and salinity has a significant effect on its physiological processes. To verify whether the calcyclin-binding [...]

The white‐blooded Antarctic icefish is the only known vertebrate lacking oxygen‐transporting haemoglobins. Fish skin mucus, as the first line of defence against pathogens, can reflect fish welfare. In this study, we analysed the skin mucus proteome profiles of the two Antarctic fish species, the white‐blooded Antarctic icefish, Chionodraco hamatus, and the red‐blooded Antarctic fish, Notothenia coriiceps, unfolding the different proteins by liquid chromatography coupled with tandem mass spectrometry isobaric tags for relative and absolute quantitation (iTRAQ) technology. Of the 4444 totally identified proteins, 227 differentially expressed proteins (DEPs) were found in the comparison between C. hamatus and N. coriiceps, of which 121 were upregulated and 106 were downregulated in the icefish. In the Kyoto Encyclopedia of Genes and Genomes pathway annotation, we found two pathways "Legionellosis" and "Complement and coagulation cascades" were significantly enriched, among of which innate immune candidate proteins such as C3, CASP1, ASC, F3 and C9 were significantly upregulated, suggesting their important roles in C. hamatus immune system. Additionally, the DEP protein–protein interaction network analysis and "Response to stress" GO category provided candidate biomarkers for deep understanding of the distinct immune response of the two Antarctic fish underlying the cold adaptation. [ABSTRACT FROM AUTHOR]

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