Antarctic fish genomes reveal how cold adaptation works

The result surprised the researchers: the maternal and paternal genomic variants were remarkably similar overall. One variant contained 17 gene copies, while the other contained 16.

Why can gene length matter in freezing water?

Bista said: “The length of the gene segments differs significantly. Since larger antifreeze proteins can inhibit the growth of ice crystals particularly effectively, these differences could help the fishes adapt to varying conditions in Antarctica.”

Antifreeze proteins inhibit ice-crystal growth, and the researchers connect the parental gene-length difference to differences in protein size. They present this relationship as a possible adaptation to varying Antarctic conditions, rather than a demonstrated cause of improved survival.

What do “jumping genes” add?

Nearly two in five of the genome consists of repetitive DNA, according to the study. Particularly common among these stretches are LINE-L2 transposons, mobile DNA segments that can move within a genome or create new copies of themselves. Their nickname, “jumping genes,” comes from that movement.

Researchers found evidence that these elements multiplied particularly rapidly at certain times during the evolution of Antarctic fishes. That expansion may have contributed to a larger genome and the emergence of new genetic variants, although the study describes this contribution as possible rather than proven.

Is antifreeze protein the whole adaptation?

Antifreeze proteins are only part of the cold-adaptation pattern. The researchers also found evidence of adaptations in genes involved in protecting cells from harmful oxidation, metabolizing fat, folding proteins correctly and maintaining important cellular functions. These processes cover the use of fats, the shapes proteins need to work and the upkeep of core cell systems.

Cold temperatures can make proteins lose their function, while the water’s high oxygen content can place additional stress on cells. Together, the gene-level findings support adaptation through several evolutionary processes rather than one isolated mechanism.

What does the study establish, and what remains uncertain?

The study offers genome-based evidence that several genetic and evolutionary processes act together. The authors’ overall conclusion is that Antarctic fishes adapted through this combination rather than through one genetic change. They keep the specific claims conditional: gene-length differences may help fish survive, and transposon expansions may contribute to genome growth and new variants.

The broader analysis compared different species, while the detailed parental comparison centered on H. antarcticus. The model-species approach supports a group-level explanation without demonstrating that every one of roughly 140 species carries the same variants. Separating parental genomes nevertheless revealed differences that conventional methods could miss.

Where was the study published?

The paper is listed as Jacopo Martelossi et al., “A new phased assembly of the Antarctic spiny plunderfish provides novel insights into the evolution of the notothenioid radiation,” in Genome Biology (2026), DOI 10.1186/s13059-026-04293-7.