The genome of the cryopelagic Antarctic bald notothen, Trematomus borchgrevinki

The Antarctic bald notothen, Trematomus borchgrevinki (family Nototheniidae) occupies a high latitude, ice-laden environment and represents an extreme example of cold-specialization among fishes. We present the first, high-quality, chromosome-scale genome of a female T. borchgrevinki individual comprised of 23 putative chromosomes, the largest of which is 65 megabasepairs (Mbp) in length. The total length of the genome 935.13 Mbp, composed of 2,094 scaffolds, with a scaffold N50 of 42.67 Mbp. Annotation yielded 22,192 protein-coding genes while 54.75% of the genome was occupied by repetitive elements; an analysis of repeats demonstrated that an expansion occurred in recent time. Conserved synteny analysis revealed that the genome architecture of T. borchgrevinki is largely maintained with other members of the notothenioid clade, although several significant translocations and inversions are present, including the fusion of orthologous chromosomes 8 and 11 into a single element. This genome will serve as a cold-specialized model for comparisons to other members of the notothenioid adaptive radiation.